Neurotrophic factor-α1 prevents stress-induced depression through enhancement of neurogenesis and is activated by rosiglitazone

Astragaloside IV plays a neuroprotective role by promoting PPARγ in cerebral ischemia-reperfusion rats

BACKGROUND

Cerebral ischemia-reperfusion injury (CIRI) usually occurs during the treatment phase of ischemic disease, which is closely related to high morbidity and mortality. Promoting neurogenesis and synaptic plasticity are effective neural recovery strategies for CIRI. Astragaloside IV (AS-IV) has been shown to play a neuroprotective role in some neurological diseases. In the current study, we evaluated the effect and possible mechanism of AS-IV in CIRI rats.

METHODS

The middle cerebral artery occlusion reperfusion (MCAO/R) model was established in rats to simulate the occurrence of human CIRI. First, we determined the cerebral injury on the 1st, 3rd, 5th and 7th day after cerebral ischemia-reperfusion (I/R) surgery by neurological deficit detection, TTC staining, TUNEL staining and Western blot analysis. Furthermore, rats were pre administered with AS-IV and then subjected to cerebral I/R surgery. Brains were collected on the 3rd day to evaluate the neuroprotective effect of AS-IV.

RESULTS

Our results showed that on the 3rd day after I/R, the neurological impairment score and infarct volume were highest, the levels of apoptosis and expression of Caspase3 and Bax reached the peak. AS-IV treatment apparently attenuated neurological dysfunction, reduced infarct volume and pathological damage, promoted the neurogenesis, and alleviated the pathological damage caused by cerebral I/R involved in thickening and blurring of synaptic membranes, reduction of microtubules and synaptic vesicles, and loss of synaptic cleft. Our study also showed that AS-IV promoted the transcription and expression of the peroxisome proliferators-activated receptors γ (PPARγ) and brain-derived neurotrophic factor (BDNF), increased the expression of phosphorylation of tyrosine kinase receptor B (TrkB) and downstream PI3K/Akt/mTOR pathway proteins. Notably, when GW9662, an inhibitor of PPARγ was administered with AS-IV, the neuroprotective effect of AS-IV was reduced.

CONCLUSIONS

These findings suggested that AS-IV has neuroprotective function in CIRI rats, and its molecular mechanism may depend on the phosphatidylinositide 3-kinase (PI3K)/protein kinase B (PKB)/Akt signalling pathway activated by PPARγ. AS-IV could be an effective therapeutic drug candidate for CIRI treatment.

Neuritin Controls Axonal Branching in Serotonin Neurons: A Possible Mediator Involved in the Regulation of Depressive and Anxiety Behaviors via FGF Signaling

Abnormal neuronal morphological features, such as dendrite branching, axonal branching, and spine density, are thought to contribute to the symptoms of depression and anxiety. However, the role and molecular mechanisms of aberrant neuronal morphology in the regulation of mood disorders remain poorly characterized. Here, we show that neuritin, an activity-dependent protein, regulates the axonal morphology of serotonin neurons. Male neuritin knock-out (KO) mice harbored impaired axonal branches of serotonin neurons in the medial prefrontal cortex and basolateral region of the amygdala (BLA), and male neuritin KO mice exhibited depressive and anxiety-like behaviors. We also observed that the expression of neuritin was decreased by unpredictable chronic stress in the male mouse brain and that decreased expression of neuritin was associated with reduced axonal branching of serotonin neurons in the brain and with depressive and anxiety behaviors in mice. Furthermore, the stress-mediated impairments in axonal branching and depressive behaviors were reversed by the overexpression of neuritin in the BLA. The ability of neuritin to increase axonal branching in serotonin neurons involves fibroblast growth factor (FGF) signaling, and neuritin contributes to FGF-2-mediated axonal branching regulation in vitro. Finally, the oral administration of an FGF inhibitor reduced the axonal branching of serotonin neurons in the brain and caused depressive and anxiety behaviors in male mice. Our results support the involvement of neuritin in models of stress-induced depression and suggest that neuronal morphological plasticity may play a role in controlling animal behavior.

miR-29a-5p rescues depressive-like behaviors in a CUMS-induced mouse model by facilitating microglia M2-polarization in the prefrontal cortex via TMEM33 suppression

BACKGROUND

Depression accounts for a high proportion of neuropsychiatric disorders and is associated with abnormal states of neurons in specific brain regions. Microglia play a pivotal role in the inflammatory state during depression development; however, the exact mechanism underlying chronic mood states remains unknown. Thus, the present study aimed to determine whether microRNAs (miRNAs) alleviate stress-induced depression-like behavior in mice by regulating the expression levels of their target genes, explore the role of neuroinflammation induced by microglial activation in the pathogenesis and progression of depression, and determine whether the role of the miR-29a-5p/transmembrane protein 33 (TMEM33) axis.

METHODS

In this study, chronic unpredictable mild stress (CUMS) mouse depression model, various behavioral tests, western blotting, dual-luciferase reporter assay, enzyme-linked immunosorbent assay, real-time quantitative reverse transcription PCR, immunofluorescence and lentivirus-mediated gene transfer were used.

RESULTS

After exposure to the CUMS paradigm, miR-29a-5p was significantly down-regulated. This downregulation subsequently promoted the polarization of microglia M1 by upregulating the expression of TMEM33, resulting in enhanced inflammatory chemokines affecting neurons. Conversely, the upregulation of miR-29a-5p within the prefrontal cortex (PFC) suppressed TMEM33 expression, facilitated microglia M2-polarization, and ameliorated depressive-like behavior.

LIMITATIONS

Only rodent models of depression were used, and human samples were not included.

CONCLUSIONS

The results of this study suggest that miR-29a-5p deficits within the PFC mediate microglial anomalies and contribute to depressive-like behaviors. miR-29a-5p and TMEM33 may, therefore, serve as potential therapeutic targets for the treatment of depression.

Exploring the molecular mechanisms of PPARγ agonists in modulating memory impairment in neurodegenerative disorders

Neurodegenerative diseases are characterized by progressive memory impairment and cognitive decline. This review aims to unravel the molecular mechanisms involved in the enhancement of memory function and mitigation of memory impairment through the activation of PPARγ agonists in neurodegenerative diseases. The findings suggest that PPARγ agonists modulate various molecular pathways involved in memory formation and maintenance. Activation of PPARγ enhances synaptic plasticity, promotes neuroprotection, suppresses neuroinflammation, attenuates oxidative stress, and regulates amyloid-beta metabolism. The comprehensive understanding of these molecular mechanisms would facilitate the development of novel therapeutic approaches targeting PPARγ to improve memory function and ultimately to alleviate the burden of neurodegenerative diseases. Further research, including clinical trials, is warranted to explore the efficacy, safety, and optimal use of specific PPARγ agonists as potential therapeutic agents in the treatment of memory impairments associated with neurodegenerative diseases.

Uncovering the effect and mechanism of Jiawei Xiaoyao Wan in treating breast cancer complicated with depression based on network pharmacology and experimental analysis

BACKGROUND

Depression is a clinically common co-morbidity in breast cancer cases that brings negative outcomes on quality of life and potentially survival. Jiawei Xiaoyao Wan (JXW) is widely used in treating breast cancer and depressive disorder, but its potential pharmacological mechanisms remain elusive.

PURPOSE

We aimed to explore the dual therapeutic effects and mechanisms of JXW acting on breast cancer complicated with depression (BCCD) by network pharmacology and in vivo experimental verification.

METHODS

The chemical constituents of JXW were characterized using liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-Q-TOF/MS). The targets related to constituents of JXW were predicted by the TCMSP and Swiss Target Prediction databases, and targets of breast cancer and depression were screened by the GeneCards and OMIM databases. Gene Ontology annotation and KEGG enrichment analysis were performed with the DAVID database. Ultimately, a BCCD mouse model induced by chronic restraint stress (CRS) was used to explore therapeutic effects and mechanisms of JXW against BCCD. The efficacy of JXW in the treatment of BCCD was evaluated based on behavioral tests, tumor volume and weight, and pathological examination. Additionally, the underlying mechanisms were explored by measuring the levels of neurotransmitter and inflammatory factors, as well as detecting the expression of genes or proteins associated with candidate targets and the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway through RT-PCR, western blotting, and immunohistochemistry.

RESULTS

Totals of 108 components were identified in JXW using LC-Q-TOF/MS. By network pharmacology analysis, 714 compound targets of JXW, 2114 breast cancer targets, 1122 depression targets, and 98 overlapping proteins were obtained. PPI network and KEGG analysis implied that TP53, ESR1, VEGFA, AKT1, IL6, TNF, EGFR and the JAK/STAT pathway might be the potential targets of JXW in treating BCCD. In vivo experiments indicated that JXW significantly ameliorated depressive symptoms and tumor progression in BCCD mice. Further mechanistic studies showed that JXW could reduce the levels of inflammatory factors, increase 5-HT level, and regulate mRNA expression levels of TP53, VEGFA, AKT1, IL6, TNF, and EGFR targets. Moreover, the expression levels of proteins related to the JAK2/STAT3 signaling pathway in BCCD mice were effectively regulated by JXW.

CONCLUSION

JXW exerts dual therapeutic effects in a BCCD mouse via multiple targets. The underlying mechanisms might be associated with regulating the levels of neurotransmitter and inflammatory factors; more importantly, the JAK2/STAT3 pathway plays a significant role in this process.

CPE correlates with poor prognosis in gastric cancer by promoting tumourigenesis

Aims

To investigate the potential functions and mechanisms of tumourigenesis in carboxypeptidase E (CPE) and its prognostic value in gastric cancer, and to develop a predictive model for prognosis based on CPE.

Results

Transcriptome level variation and the prognostic value of CPE in different types of cancers were investigated using bioinformatics analyses. The association between CPE and clinicopathological characteristics was specifically explored in gastric cancer. Elevated CPE expression was associated with poor survival and recurrence prognosis and was found in cases with a later clinical stage of gastric cancer. The CPE was considered an independent prognostic factor, as assessed using Cox regression analysis. The prognostic value of CPE was further verified through immunohistochemistry and haematoxylin staining. Enrichment analysis provided a preliminary confirmation of the potential functions and mechanisms of CPE. Immune cell infiltration analysis revealed a significant correlation between CPE and macrophage infiltration. Eventually, a prognosis prediction nomogram model based on CPE was developed.

Conclusion

CPE was identified as an independent biomarker associated with poor prognosis in gastric cancer. This suggests that CPE overexpression promoted epithelial-mesenchymal transition via the activation of the Erk/Wnt pathways, leading to proliferation, invasion, and metastasis. Targeted therapeutic strategies for gastric cancer may benefit from these findings.

Agomirs upregulating carboxypeptidase E expression rescue hippocampal neurogenesis and memory deficits in Alzheimer's disease

BACKGROUND

Adult neurogenesis occurs in the subventricular zone (SVZ) and the subgranular zone of the dentate gyrus in the hippocampus. The neuronal stem cells in these two neurogenic niches respond differently to various physiological and pathological stimuli. Recently, we have found that the decrement of carboxypeptidase E (CPE) with aging impairs the maturation of brain-derived neurotrophic factor (BDNF) and neurogenesis in the SVZ. However, it remains unknown whether these events occur in the hippocampus, and what the role of CPE is in the adult hippocampal neurogenesis in the context of Alzheimer's disease (AD).

METHODS

In vivo screening was performed to search for miRNA mimics capable of upregulating CPE expression and promoting neurogenesis in both neurogenic niches. Among these, two agomirs were further assessed for their effects on hippocampal neurogenesis in the context of AD. We also explored whether these two agomirs could ameliorate behavioral symptoms and AD pathology in mice, using direct intracerebroventricular injection or by non-invasive intranasal instillation.

RESULTS

Restoration of CPE expression in the hippocampus improved BDNF maturation and boosted adult hippocampal neurogenesis. By screening the miRNA mimics targeting the 5'UTR region of Cpe gene, we developed two agomirs that were capable of upregulating CPE expression. The two agomirs significantly rescued adult neurogenesis and cognition, showing multiple beneficial effects against the AD-associated pathologies in APP/PS1 mice. Of note, noninvasive approach via intranasal delivery of these agomirs improved the behavioral and neurocognitive functions of APP/PS1 mice.

CONCLUSIONS

CPE may regulate adult hippocampal neurogenesis via the CPE-BDNF-TrkB signaling pathway. This study supports the prospect of developing miRNA agomirs targeting CPE as biopharmaceuticals to counteract aging- and disease-related neurological decline in human brains.

Converged avenues: depression and Alzheimer's disease- shared pathophysiology and novel therapeutics

Depression, a highly prevalent disorder affecting over 280 million people worldwide, is comorbid with many neurological disorders, particularly Alzheimer's disease (AD). Depression and AD share overlapping pathophysiology, and the search for accountable biological substrates made it an essential and intriguing field of research. The paper outlines the neurobiological pathways coinciding with depression and AD, including neurotrophin signalling, the hypothalamic-pituitary-adrenal axis (HPA), cellular apoptosis, neuroinflammation, and other aetiological factors. Understanding overlapping pathways is crucial in identifying common pathophysiological substrates that can be targeted for effective management of disease state. Antidepressants, particularly monoaminergic drugs (first-line therapy), are shown to have modest or no clinical benefits. Regardless of the ineffectiveness of conventional antidepressants, these drugs remain the mainstay for treating depressive symptoms in AD. To overcome the ineffectiveness of traditional pharmacological agents in treating comorbid conditions, a novel therapeutic class has been discussed in the paper. This includes neurotransmitter modulators, glutamatergic system modulators, mitochondrial modulators, antioxidant agents, HPA axis targeted therapy, inflammatory system targeted therapy, neurogenesis targeted therapy, repurposed anti-diabetic agents, and others. The primary clinical challenge is the development of therapeutic agents and the effective diagnosis of the comorbid condition for which no specific diagnosable scale is present. Hence, introducing Artificial Intelligence (AI) into the healthcare system is revolutionary. AI implemented with interdisciplinary strategies (neuroimaging, EEG, molecular biomarkers) bound to have accurate clinical interpretation of symptoms. Moreover, AI has the potential to forecast neurodegenerative and psychiatric illness much in advance before visible/observable clinical symptoms get precipitated.

Carboxypeptidase E conditional knockout mice exhibit learning and memory deficits and neurodegeneration

Carboxypeptidase E (CPE) is a multifunctional protein with many nonenzymatic functions in various systems. Previous studies using CPE knock-out mice have shown that CPE has neuroprotective effects against stress and is involved in learning and memory. However, the functions of CPE in neurons are still largely unknown. Here we used a Camk2a-Cre system to conditionally knockout CPE in neurons. The wild-type, CPE^flox/-, and CPE^flox/flox mice were weaned, ear-tagged, and tail clipped for genotyping at 3 weeks old, and they underwent open field, object recognition, Y-maze, and fear conditioning tests at 8 weeks old. The CPE^flox/flox mice had normal body weight and glucose metabolism. The behavioral tests showed that CPE^flox/flox mice had impaired learning and memory compared with wild-type and CPE^flox/- mice. Surprisingly, the subiculum (Sub) region of CPE^flox/flox mice was completely degenerated, unlike the CPE full knockout mice, which exhibit CA3 region neurodegeneration. In addition, doublecortin immunostaining suggested that neurogenesis in the dentate gyrus of the hippocampus was significantly reduced in CPE^flox/flox mice. Interestingly, TrkB phosphorylation in the hippocampus was downregulated in CPE^flox/flox mice, but brain-derived neurotrophic factor levels were not. In both the hippocampus and dorsal medial prefrontal cortex, we observed reduced MAP2 and GFAP expression in CPE^flox/flox mice. Taken together, the results of this study demonstrate that specific neuronal CPE knockout leads to central nervous system dysfunction in mice, including learning and memory deficits, hippocampal Sub degeneration and impaired neurogenesis.

Anti-depressant-like effects of rannasangpei and its active ingredient crocin-1 on chronic unpredictable mild stress mice

Major depressive disorder is one of the most common neuropsychiatric diseases and it is a global public health problem that leads to disabilities. Currently, there is a growing need to explore novel strategy to cure major depressive disorder due to the limitation of available treatments. Rannasangpei (RSNP) is a traditional Tibetan medicine which acts as a therapeutic agent in various acute or chronic diseases, including cardiovascular diseases and neurodegenerative diseases. Crocin-1 a coloring ingredient of saffron which exhibited anti-oxidative and anti-inflammatory properties. Here, we aimed to illustrate whether RSNP and its active ingredient crocin-1 rescue depressive-like phenotypes in chronic unpredictable mild stress (CUMS) induced mouse model of depression. Our results showed that peripheral administration of RSNP or crocin-1 ameliorated the depressive-like behaviors in CUMS-treated mice, as demonstrated by the forced swimming test and tail suspension test. Furthermore, RSNP or crocin-1 treatment reduced oxidative stress in the peripheral blood and hippocampus of the CUMS-treated mice. Additionally, the dysregulated immune system response, as demonstrated by the increased expression of the pro-inflammatory factors (tumor necrosis factor-α and interleukin-6) and the decreased expression of the anti-inflammatory factor-interleukin-10 in the prefrontal cortex and/or hippocampus of CUMS-treated mice, were at least partially restored by RSNP or crocin-1 treatment. RSNP or crocin-1 also restored apoptotic protein marker (Bcl-2 and Bax) levels in the prefrontal cortex and hippocampus of the CUMS-treated mice. Moreover, our data indicated that RSNP or crocin-1 increased astrocyte number and brain-derived neurotrophic factor levels in the hippocampus of CUMS-treated mice after RSNP or crocin-1 administration. Taken together, our study for the first time revealed an anti-depressant effect of RSNP and its active ingredient crocin-1 in a mouse model of depression, with involvement of oxidative stress, inflammatory response and apoptotic pathway.

Antidepressant-like effects of trophic factor receptor signaling

A significant body of research has demonstrated that antidepressants regulate neurotrophic factors and that neurotrophins themselves are capable of independently producing antidepressant-like effects. While brain derived neurotrophic factor (BDNF) remains the best studied molecule in this context, there are several structurally diverse trophic factors that have shown comparable behavioral effects, including basic fibroblast growth factor (FGF-2), insulin-like growth factor 1 (IGF-1) and vascular endothelial growth factor (VEGF). In this review we discuss the structural and biochemical signaling aspects of these neurotrophic factors with antidepressant activity. We also include a discussion on a cytokine molecule erythropoietin (EPO), widely known and prescribed as a hormone to treat anemia but has recently been shown to function as a neurotrophic factor in the central nervous system (CNS).

Mechanism of Neural Regeneration Induced by Natural Product LY01 in the 5×FAD Mouse Model of Alzheimer's Disease

Background: A sharp decline in neural regeneration in patients with Alzheimer's disease (AD) exacerbates the decline of cognition and memory. It is of great significance to screen for innovative drugs that promote endogenous neural regeneration. Cytisine N-methylene-(5,7,4'-trihydroxy)-isoflavone (LY01) is a new compound isolated from the Chinese herbal medicine Sophora alopecuroides with both isoflavone and alkaloid characteristic structures. Its pharmacological effects are worth studying. Objective: This study was designed to determine whether LY01 delays the cognitive and memory decline in the early stage of AD and whether this effect of LY01 is related to promoting neural regeneration. Methods: Eight-week-old 5×Familial Alzheimer's Disease (5×FAD) mice were used as disease models of early AD. Three doses of LY01 administered in two courses (2 and 5 weeks) of treatment were tested. Cognition, memory, and anxiety-like behaviors in mice were evaluated by the Morris water maze, fear conditioning, and open field experiments. Regeneration of neurons in the mouse hippocampus was observed using immunofluorescence staining. The effect of LY01 on cell regeneration was also demonstrated using a series of tests on primary cultured neurons, astrocytes, and neural stem cells (NSCs). In addition, flow cytometry and transcriptome sequencing were carried out to preliminarily explored the mechanisms. Results: We found that LY01 reduced the decline of cognition and memory in the early stage of 5×FAD mice. This effect was related to the proliferation of astrocytes, the proliferation and migration of NSCs, and increases in the number of new cells and neural precursor cells in the dentate gyrus area of 5×FAD mice. This phenomenon could be observed both in 2-week-old female and 5-week-old male LY01-treated 5×FAD mice. The neuronal regeneration induced by LY01 was related to the regulation of the extracellular matrix and associated receptors, and effects on the S phase of the cell cycle. Conclusion: LY01 increases the proliferation of NSCs and astrocytes and the number of neural precursor cells in the hippocampus, resulting in neural regeneration in 5×FAD mice by acting on the extracellular matrix and associated receptors and regulating the S phase of the cell cycle. This provides a new idea for the early intervention and treatment of AD.

Neurotrophic Factor-α1/Carboxypeptidase E Functions in Neuroprotection and Alleviates Depression

Depression is a major psychiatric disease affecting all ages and is often co-morbid with neurodegeneration in the elderly. Depression and neurodegeneration are associated with decreased neurotrophic factors. In this mini-review the functions and potential therapeutic use of a newly discovered trophic factor, Neurotrophic factor-α1 (NF-α1), also known as Carboxypeptidase E (CPE), in depression and neuroprotection are discussed. NF-α1/CPE expression is enriched in CA3 neurons of the hippocampus. Families carrying null and homozygous non-sense mutations of the NF-α1/CPE gene share common clinical features including childhood onset obesity, type 2 diabetes, impaired intellectual abilities and hypogonadotrophic hypogonadism. Studies in animal models such as CPE knockout (KO) mice and CPEfat/fat mutant mice exhibit similar phenotypes. Analysis of CPE-KO mouse brain revealed that hippocampal CA3 was completely degenerated after weaning stress, along with deficits in hippocampal long-term potentiation. Carbamazepine effectively blocked weaning stress-induced hippocampal CA3 degeneration, suggesting the stress induced epileptic-like neuronal firing led to the degeneration. Analysis of possible mechanisms underlying NF-α1/CPE -mediated neuroprotection revealed that it interacts with the serotonin receptor, 5-HTR1E, and via β arrestin activation, subsequently upregulates ERK1/2 signaling and pro-survival protein, BCL2, levels. Furthermore, the NF-α1/CPE promoter contains a peroxisome proliferator-activated receptor (PPARγ) binding site which can be activated by rosiglitazone, a PPARγ agonist, to up-regulate expression of NF-α1/CPE and neurogenesis, resulting in anti-depression in animal models. Rosiglitazone, an anti-diabetic drug administered to diabetic patients resulted in decline of depression. Thus, NF-α1/CPE is a potential therapeutic agent or drug target for treating depression and neurodegenerative disorders.

Intranasal Administration of Brain-Derived Neurotrophic Factor Rescues Depressive-Like Phenotypes in Chronic Unpredictable Mild Stress Mice

INTRODUCTION

Major depression disorder is the most common diagnosed mental illnesses, and it bring a high social and economic burden. However, the current treatment for depression has limitations with side effects. Hence, there is an urgent need to search more effective treatment for major depressive disorder. Brain-derived neurotrophic factor (BDNF) is a neurotrophin that is vital to the survival, growth, and maintenance of neurons.

METHODS

We administered BDNF into chronic unpredictable mild stress (CUMS)-induced depression mice and assessed the effects of intranasal delivery of BDNF in depression by the tail suspension test, forced swimming test, novelty suppressed feeding test, and open-field test.

RESULTS

We find that the intranasal administration of BDNF reversed the depressive-like behaviors in CUMS mice as measured Further analyses suggested that BDNF treatment reduced pro-inflammatory cytokine (IL-6, TNF-α, iNOS and IL-1β) expressions in the hippocampus of CUMS mice. In addition, our results showed that BDNF markedly reduced oxidative stress in the hippocampus and blood of CUMS mice. Moreover, our data suggested that BDNF treatment increased neurogenesis in the hippocampus of CUMS mice.

DISCUSSION

Taken together, our results for the first time demonstrated that intranasal delivery of BDNF protein exhibited anti-depressant-like effects in mice, and therefore may represent a new therapeutic strategy for major depressive disorder.

Carboxypeptidase E Independently Changes Microtubule Glutamylation, Dendritic Branching, and Neuronal Migration

Neuronal migration and dendritogenesis are dependent on dynamic changes to the microtubule (MT) network. Among various factors that regulate MT dynamics and stability, post-translational modifications (PTMs) of MTs play a critical role in conferring specificity of regulatory protein binding to MTs. Thus, it is important to understand the regulation of PTMs during brain development as multiple developmental processes are dependent on MTs. In this study, we identified that carboxypeptidase E (CPE) changes tubulin polyglutamylation, a major PTM in the brain, and we examine the impact of CPE-mediated changes to polyglutamylation on cortical neuron migration and dendrite morphology. We show, for the first time, that overexpression of CPE increases the level of polyglutamylated α-tubulin while knockdown decreases the level of polyglutamylation. We also demonstrate that CPE-mediated changes to polyglutamylation are dependent on the CPE zinc-binding motif and that this motif is necessary for CPE action on p150^Glued localization. However, overexpression of a CPE mutant that does not increase MT glutamylation mimics the effects of overexpression of wild type CPE on dendrite branching. Furthermore, although overexpression of wild type CPE does not alter cortical neuron migration, overexpression of the mutant may act in a dominant-negative manner as it decreases the number of neurons that reach the cortical plate (CP), as we previously reported for CPE knockdown. Overall, our data suggest that CPE changes MT glutamylation and redistribution of p150^Glued and that this function of CPE is independent of its role in shaping dendrite development but plays a partial role in regulating cortical neuron migration.

FGF binding protein 3 is required for spinal cord motor neuron development and regeneration in zebrafish

Fibroblast growth factor binding protein 3 (Fgfbp3) have been known to be crucial for the process of neural proliferation, differentiation, migration, and adhesion. However, the specific role and the molecular mechanisms of fgfbp3 in regulating the development of motor neurons remain unclear. In this study, we have investigated the function of fgfbp3 in morphogenesis and regeneration of motor neuron in zebrafish. Firstly, we found that fgfbp3 was localized in the motor neurons and loss of fgfbp3 caused the significant decrease of the length and branching number of the motor neuron axons, which could be partially rescued by fgfbp3 mRNA injection. Moreover, the fgfbp3 knockdown (KD) embryos demonstrated similar defects of motor neurons as identified in fgfbp3 knockout (KO) embryos. Furthermore, we revealed that the locomotion and startle response of fgfbp3 KO embryos were significantly restricted, which were partially rescued by the fgfbp3 overexpression. In addition, fgfbp3 KO remarkably compromised axonal regeneration of motor neurons after injury. Lastly, the malformation of motor neurons in fgfbp3 KO embryos was rescued by overexpressing drd1b or neurod6a, respectively, which were screened by transcriptome sequencing. Taken together, our results provide strong cellular and molecular evidence that fgfbp3 is crucial for the axonal morphogenesis and regeneration of motor neurons in zebrafish.

Altered Peripheral Immune Profiles in First-Episode, Drug-Free Patients With Schizophrenia: Response to Antipsychotic Medications

Previous research has demonstrated aberrations in the levels of inflammatory cytokines in patients with schizophrenia (SCZ), but most of the respective studies have tested a narrow set of inflammatory cytokines. Here, we aimed to analyze broad immune profiles in the peripheral blood of the first-episode drug-free (FEDF) patients with SCZ at baseline and after an 8-week treatment with atypical antipsychotics. Serum samples from 24 FEDF patients with SCZ and 25 healthy control (HC) subjects were tested using Luminex multiplex analysis for 30 cytokines, chemokines, and growth factors. Multiple comparison tests demonstrated that interleukin-2 (IL-2), IL-4, interferon-gamma (IFN-γ), monokine induced by IFN-γ, and granulocyte colony-stimulating factor (G-CSF) levels were significantly increased, whereas those of the epidermal growth factor were significantly decreased in the FEDF patients with SCZ. Moreover, the levels of the 6 dysregulated cytokines as well as those of 12 additional soluble factors in FEDF patients with SCZ were significantly decreased after 8 weeks of antipsychotic treatment. Furthermore, the transcription of G-CSF and IFN-γ was significantly increased in FEDF patients with SCZ when compared with controls, and G-CSF and IFN-γ mRNA levels were highly correlated with their respective protein concentrations. Receiver operating characteristic curves showed that G-CSF and IFN-γ had good performance in differentiating between FEDF patients with SCZ and HC subjects. Taken together, our data revealed that FEDF patients with SCZ were accompanied by a unique pattern of immune profile, and antipsychotic medications seemed to suppress the immune function in these patients, which could be used to develop novel targets for the diagnosis and treatment of SCZ.

Sex and region-specific effects of variable stress on microglia morphology

Major Depressive Disorder (MDD) is a common and debilitating mood disorder that is more prevalent in women than men. In humans, PET imaging of microglia activation is currently being explored as a potential biomarker of MDD and suicidal ideation. Stress is a trigger for many mood disorders, including MDD. Microglial changes in morphology and activation state in response to stress has been reported in various brain regions, but most studies only examined male subjects. Here we report changes in microglia morphology in the nucleus accumbens (NAc) and subregions of the hippocampus (HPC) in both male and female mice following variable stress of 6 or 28 days in duration. Our data demonstrate that after 6 days of stress, microglia in the female NAc and dentate gyrus have a reduction in homeostatic associated morphology and an increase in primed microglia. After 28 days some of these sex specific stress effects were still present in microglia within the NAc but not the dentate gyrus. There were no effects of stress in either sex at either timepoint in CA1. In female mice, anti-inflammatory activation of microglia using rosiglitazone promoted sociability behavior after 6 days of stress. Furthermore, both drug and stress have impact on microglia morphology and activation state in the NAc. These data suggest that microglia morphology and activation state are altered by 6 days of variable stress in a region-specific manner and may contribute to, or potentially compensate for, the onset of stress susceptibility rather than impacting long term exposure to stress.

Blood-Brain Barrier Dysfunction in the Pathogenesis of Major Depressive Disorder

Major depression represents a complex and prevalent psychological disease that is characterized by persistent depressed mood, impaired cognitive function and complicated pathophysiological and neuroendocrine alterations. Despite the multifactorial etiology of depression, one of the most recent factors to be identified as playing a critical role in the development of depression is blood-brain barrier (BBB) disruption. The occurrence of BBB integrity disruption contributes to the disturbance of brain homeostasis and leads to complications of neurological diseases, such as stroke, chronic neurodegenerative disorders, neuroinflammatory disorders. Recently, BBB associated tight junction disruption has been shown to implicate in the pathophysiology of depression and contribute to increased susceptibility to depression. However, the underlying mechanisms and importance of BBB damage in depression remains largely unknown. This review highlights how BBB disruption regulates the depression process and the possible molecular mechanisms involved in development of depression-induced BBB dysfunction. Moreover, insight on promising therapeutic targets for treatment of depression with associated BBB dysfunctions are also discussed.

Impact of depression and stress on placental DNA methylation in ethnically diverse pregnant women

Aim: To investigate the association between placental genome-wide methylation at birth and antenatal depression and stress during pregnancy. Methods: We examined the association between placental genome-wide DNA methylation (n = 301) and maternal depression and stress assessed at six gestation periods during pregnancy. Correlation between DNA methylation at the significantly associated CpGs and expression of nearby genes in the placenta was tested. Results: Depression and stress were associated with methylation of 16 CpGs and two CpGs, respectively, at a 5% false discovery rate. Methylation levels at two of the CpGs associated with depression were significantly associated with expression of ADAM23 and CTDP1, genes implicated in neurodevelopment and neuropsychiatric diseases. Conclusion: Placental epigenetic changes linked to antenatal depression suggest potential fetal brain programming. Clinical trial registration number: NCT00912132 (ClinicalTrials.gov).

The Role of Fgf9 in the Antidepressant Effects of Exercise and Fluoxetine in Chronic Unpredictable Mild Stress Mice

OBJECTIVE

The neurotrophic hypothesis of depression posits that stress and depression decrease neurotrophic factor expression in brain, whereas antidepressants and exercise can contribute to the blockade of stress effects and produce antidepressant effects. Fibroblast growth factor 9 (FGF9), a member of the fibroblast growth factor (FGF) family, has been reported to be dysregulated in depression. The present study aimed to determine whether and how Fgf9 mediates the antidepressant effects of fluoxetine and exercise in chronic unpredictable mild stress (CUMS) mice.

METHODS

Male C57BL/6 mice were exposed to CUMS for 7 weeks. From the fourth week, CUMS-exposed mice were subjected to fluoxetine treatment or swimming exercise for 4 weeks. Forced swim test, tail suspension test, and hole-board test were used to assess behaviors of mice. Real-time polymerase chain reaction was used to examine hippocampal messenger RNA levels of Fgf9, Fgf2, FgfR1, FgfR2, and FgfR3. Western blotting was used to examine the protein levels of Fgf9, protein kinase B (Akt), and phosphorylation of Akt at Ser473 in mouse hippocampus.

RESULTS

Our results demonstrated that CUMS induced depression-like behaviors, which were reversed by fluoxetine treatment and swimming exercise. Moreover, we found that CUMS resulted in a dysregulation of Fgf9, Fgf2, and FgfR2 expression, whereas fluoxetine and swimming restored the FGF expression in CUMS-exposed mice. An analysis of the proteins suggests that the antidepressant effects of fluoxetine and exercise in CUMS-exposed mice were associated with ameliorated Fgf9/Akt signaling.

CONCLUSIONS

Our findings have demonstrated that swimming exercise mimics the antidepressant effects of fluoxetine by regulating Fgf9 in CUMS-exposed mice, which may offer new mechanism-based therapeutic targets for depression.

Peroxisome proliferator-activated receptor gamma: a novel therapeutic target for cognitive impairment and mood disorders that functions via the regulation of adult neurogenesis

The proliferation, differentiation, and migration of neural precursor cells occur not only during embryonic development but also within distinct regions of the adult brain through the process of adult neurogenesis. As neurogenesis can potentially regulate brain cognition and neuronal plasticity, the factors that enhance neurogenesis can be attractive therapeutic targets for improving cognitive function and regulating neurodegenerative and neuropsychiatric disorders, including affective and mood disorders. Peroxisome proliferator-activated receptors (PPARs) are a class of ligand-activated transcription factors belonging to the nuclear receptor superfamily. PPARγ is a target for insulin sensitizers and plays an essential role in regulating various metabolic processes, including adipogenesis and glucose homeostasis. Interestingly, evidence demonstrates the role of PPARγ activation in regulating neurogenesis. The pharmacological activation of PPARγ using specific ligands increases the proliferation and differentiation of neural stem cells in specific brain regions, including the hippocampus, and prevents neurodegeneration and improves cognition and anxiety/depression-like behaviors in animal models. We summarize here recent reports on the role of PPARγ in adult neurogenesis, as well as the mechanisms involved, and suggest that PPARγ can serve as a potential therapeutic target for neurological and/or neurodegenerative diseases.

Takeda G Protein-Coupled Receptor 5 Modulates Depression-like Behaviors via Hippocampal CA3 Pyramidal Neurons Afferent to Dorsolateral Septum

BACKGROUND

Takeda G protein-coupled receptor 5 (TGR5) is recognized as a promising target for type 2 diabetes and metabolic syndrome; its expression has been demonstrated in the brain and is thought to be neuroprotective. Here, we hypothesize that dysfunction of central TGR5 may contribute to the pathogenesis of depression.

METHODS

In well-established chronic social defeat stress (CSDS) and chronic restraint stress (CRS) models of depression, we investigated the functional roles of TGR5 in CA3 pyramidal neurons (PyNs) and underlying mechanisms of the neuronal circuit in depression (for in vivo studies, n = 10; for in vitro studies, n = 5-10) using fiber photometry; optogenetic, chemogenetic, pharmacological, and molecular profiling techniques; and behavioral tests.

RESULTS

Both CSDS and CRS most significantly reduced TGR5 expression of hippocampal CA3 PyNs. Genetic overexpression of TGR5 in CA3 PyNs or intra-CA3 infusion of INT-777, a specific agonist, protected against CSDS and CRS, exerting significant antidepressant-like effects that were mediated via CA3 PyN activation. Conversely, genetic knockout or TGR5 knockdown in CA3 facilitated stress-induced depression-like behaviors. Re-expression of TGR5 in CA3 PyNs rather than infusion of INT-777 significantly improved depression-like behaviors in Tgr5 knockout mice exposed to CSDS or CRS. Silencing and stimulation of CA3 PyNs→somatostatin-GABAergic (gamma-aminobutyric acidergic) neurons of the dorsolateral septum circuit bidirectionally regulated depression-like behaviors, and blockade of this circuit abrogated the antidepressant-like effects from TGR5 activation of CA3 PyNs.

CONCLUSIONS

These findings indicate that TGR5 can regulate depression via CA3 PyNs→somatostatin-GABAergic neurons of dorsolateral septum transmission, suggesting that TGR5 could be a novel target for developing antidepressants.

PTEN in prefrontal cortex is essential in regulating depression-like behaviors in mice

Chronic stress is an environmental risk factor for depression and causes neuronal atrophy in the prefrontal cortex (PFC) and other brain regions. It is still unclear about the molecular mechanism underlying the behavioral alterations and neuronal atrophy induced by chronic stress. We here report that phosphatase and tensin homolog deleted on chromosome ten (PTEN) is a mediator for chronic stress-induced depression-like behaviors and neuronal atrophy in mice. One-month chronic restraint stress (CRS) up-regulated PTEN signaling pathway in the PFC of mice as indicated by increasing levels of PTEN, p-MEK, and p-ERK but decreasing levels of p-AKT. Over-expression of Pten in the PFC led to an increase of depression-like behaviors, whereas genetic inactivation or knockdown of Pten in the PFC prevented the CRS-induced depression-like behaviors. In addition, systemic administration of PTEN inhibitor was also able to prevent these behaviors. Cellular examination showed that Pten over-expression or the CRS treatment resulted in PFC neuron atrophy, and this atrophy was blocked by genetic inactivation of Pten or systemic administration of PTEN inhibitor. Furthermore, possible causal link between Pten and glucocorticoids was examined. In chronic dexamethasone (Dex, a glucocorticoid agonist) treatment-induced depression model, increased PTEN levels were observed, and depression-like behaviors and PFC neuron atrophy were attenuated by the administration of PTEN inhibitor. Our results indicate that PTEN serves as a key mediator in chronic stress-induced neuron atrophy as well as depression-like behaviors, providing molecular evidence supporting the synaptic plasticity theory of depression.

Advances in novel molecular targets for antidepressants

Depression is the most common psychiatric illness affecting numerous people world-wide. The currently available antidepressant treatment presents low response and remission rates. Thus, new effective antidepressants need to be developed or discovered. Aiming to give an overview of novel possible antidepressant drug targets, we summarized the molecular targets of antidepressants and the underlying neurobiology of depression. We have also addressed the multidimensional perspectives on the progress in the psychopharmacological treatment of depression and on the new potential approaches with effective drug discovery.

Neurotrophic factor-α1, a novel tropin is critical for the prevention of stress-induced hippocampal CA3 cell death and cognitive dysfunction in mice: comparison to BDNF

Stress leads to brain pathology including hippocampal degeneration, cognitive dysfunction, and potential mood disorders. Hippocampal CA3, a most stress-vulnerable region, consists of pyramidal neurons that regulate cognitive functions e.g. learning and memory. These CA3 neurons express high levels of the neuroprotective protein, neurotrophic factor-α1 (NF-α1), also known as carboxypeptidase E (CPE), and receive contacts from granule cell projections that release BDNF which has neuroprotective activity. Whether NF-α1-CPE and/or BDNF are critical in protecting these CA3 neurons against severe stress-induced cell death is unknown. Here we show that social combined with the physical stress of maternal separation, ear tagging, and tail snipping at weaning in 3-week-old mice lacking NF-α1-CPE, led to complete hippocampal CA3 degeneration, despite having BDNF and active phosphorylated TrkB receptor levels similar to WT animals. Mice administered TrkB inhibitor, ANA12 which blocked TrkB phosphorylation showed no degeneration of the CA3 neurons after the weaning stress paradigm. Furthermore, transgenic knock-in mice expressing CPE-E342Q, an enzymatically inactive form, replacing NF-α1-CPE, showed no CA3 degeneration and exhibited normal learning and memory after the weaning stress, unlike NF-α1-CPE-KO mice. Mechanistically, we showed that radio-labeled NF-α1-CPE bound HT22 hippocampal cells in a saturable manner and with high affinity (Kd = 4.37 nM). Subsequently, treatment of the HT22^cpe-/- cells with NF-α1-CPE or CPE-E342Q equivalently activated ERK signaling and increased BCL2 expression to protect these neurons against H₂O₂-or glutamate-induced cytotoxicity. Our findings show that NF-α1-CPE is more critical compared to BDNF in protecting CA3 pyramidal neurons against stress-induced cell death and cognitive dysfunction, independent of its enzymatic activity.

Nonenzymatic and Trophic Activities of Carboxypeptidase E Regulate Bone Mass and Bioenergetics of Skeletal Stem Cells in Mice

Bone and energy metabolism are integrated by common regulatory mechanisms. Carboxypeptidase E (CPE), also known as obesity susceptibility protein or neurotrophic factor‐α1, is recognized for its function in processing prohormones, including proinsulin and pro‐opiomelanocortin polypeptide. Independent of its enzymatic activity, CPE may also act as a secreted factor with divergent roles in neuroprotection and cancer growth; however, its role in the regulation of bone mass and skeletal cell differentiation is unknown. Male mice with global deficiency in CPE are characterized with profound visceral obesity, low bone mass in both appendicular and axial skeleton, and high volume of marrow fat. Interestingly, although metabolic deficit of CPE KO mice develops early in life, bone deficit develops in older age, suggesting that CPE bone‐specific activities differ from its enzymatic activities. Indeed, mutated CPE knockin (mCPE KI) mice ectopically expressing CPE‐E342Q, a mutated protein lacking enzymatic activity, develop the same obese phenotype and accumulate the same volume of marrow fat as CPE KO mice, but their bone mass is normal. In addition, differentiation of marrow hematopoietic cells toward tartrate‐resistant acid phosphatase‐positive multinucleated osteoclasts is highly increased in CPE KO mice, but normal in mCPE KI mice. Moreover, in murine skeletal stem cells, nonenzymatic trophic CPE has activated ERK signaling, increased cell proliferation and increased mitochondrial activity. Treatment of preosteoblastic cells with intact or mutated recombinant CPE led to a transient accumulation of small lipid droplets, increased oxidative phosphorylation, and increased cellular dependence on fatty acids as fuel for energy production. In human marrow aspirates, CPE expression increases up to 30‐fold in osteogenic conditions. These findings suggest that nonenzymatic and trophic activities of CPE regulate bone mass, whereas marrow adiposity is controlled by CPE enzymatic activity. Thus, CPE can be positioned as a factor regulating simultaneously bone and energy metabolism through a combination of shared and distinct mechanisms. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

The Emerging Role of SGK1 (Serum- and Glucocorticoid-Regulated Kinase 1) in Major Depressive Disorder: Hypothesis and Mechanisms

Major depressive disorder (MDD) is a heterogeneous psychiatric disease characterized by persistent low mood, diminished interests, and impaired cognitive and social functions. The multifactorial etiology of MDD is still largely unknown because of the complex genetic and environmental interactions involved. Therefore, no established mechanism can explain all the aspects of the disease. In this light, an extensive research about the pathophysiology of MDD has been carried out. Several pathogenic hypotheses, such as monoamines deficiency and neurobiological alterations in the stress-responsive system, including the hypothalamic-pituitary-adrenal (HPA) axis and the immune system, have been proposed for MDD. Over time, remarkable studies, mainly on preclinical rodent models, linked the serum- and glucocorticoid-regulated kinase 1 (SGK1) to the main features of MDD. SGK1 is a serine/threonine kinase belonging to the AGK Kinase family. SGK1 is ubiquitously expressed, which plays a pivotal role in the hormonal regulation of several ion channels, carriers, pumps, and transcription factors or regulators. SGK1 expression is modulated by cell stress and hormones, including gluco- and mineralocorticoids. Compelling evidence suggests that increased SGK1 expression or function is related to the pathogenic stress hypothesis of major depression. Therefore, the first part of the present review highlights the putative role of SGK1 as a critical mediator in the dysregulation of the HPA axis, observed under chronic stress conditions, and its controversial role in the neuroinflammation as well. The second part depicts the negative regulation exerted by SGK1 in the expression of both the brain-derived neurotrophic factor (BDNF) and the vascular endothelial growth factor (VEGF), resulting in an anti-neurogenic activity. Finally, the review focuses on the antidepressant-like effects of anti-oxidative nutraceuticals in several preclinical model of depression, resulting from the restoration of the physiological expression and/or activity of SGK1, which leads to an increase in neurogenesis. In summary, the purpose of this review is a systematic analysis of literature depicting SGK1 as molecular junction of the complex mechanisms underlying the MDD in an effort to suggest the kinase as a potential biomarker and strategic target in modern molecular antidepressant therapy.

Exosomes from patients with major depression cause depressive-like behaviors in mice with involvement of miR-139-5p-regulated neurogenesis

Exosomal microRNAs (miRNAs) have been suggested to participate in the pathogenesis of neuropsychiatric diseases, but their role in major depressive disorder (MDD) is unknown. We performed a genome-wide miRNA expression profiling of blood-derived exosomes from MDD patients and control subjects and revealed the top differentially expressed exosomal miRNA, i.e. hsa-miR-139-5p (upregulation), had good performance to differentiate between MDD patients and controls. Tail vein injection of blood exosomes isolated from MDD patients into normal mice caused their depressive-like behaviors as determined by the forced swimming, tail suspension, and novelty suppressed feeding tests, and injection of blood exosomes isolated from healthy volunteers into unpredictable mild stress (CUMS)-treated mice alleviated their depressive-like behaviors. CUMS mice also showed significantly increased blood and brain levels of exosomal miR-139-5p. Furthermore, the depressive-like behaviors in CUMS-treated mice were rescued by intranasal injection of miR-139-5p antagomir, suggesting that increased exosomal miR-139-5p levels may mediate stress-induced depression-like behavior in mice. Both exosome treatment and miR-139-5p antagomir treatment increased hippocampal neurogenesis in the CUMS-treated mice, and treatment of exosome from MDD patients decreased hippocampal neurogenesis in the normal mice. The role of miR-139-5p in neurogenesis was validated by in vitro experiments, demonstrating that miR-139-5p is a negative regulator for neural stem cell proliferation and neuronal differentiation. Our findings together suggest that exosomes from patients with major depression caused depressive-like behaviors in mice with involvement of miR-139-5p-regulated neurogenesis. Therefore, exosomal miRNAs are promising targets for the diagnosis and treatment of MDD.

Low and High Molecular Weight FGF-2 Have Differential Effects on Astrocyte Proliferation, but Are Both Protective Against Aβ-Induced Cytotoxicity

Astrocytes are the most abundant type of glial cells in the brain, and they play a key role in Alzheimer’s disease (AD). Fibroblast Growth Factor-2 (FGF-2) has been implicated as a potential therapeutic agent for treating AD. In the present study, we investigated the protective effects of low molecular weight (LMW; 17 KDa) and high molecular weight (HMW; 23 KDa) forms of FGF-2 on Aβ_1–42-induced toxicity, and proliferation in astrocytes. We show that both isoforms of FGF-2 have similar protective effects against Aβ_1–42-induced cytotoxicity in primary cultured cortical astrocytes as measured by Lactate Dehydrogenase (LDH) release assay. Additionally, 17 KDa FGF-2 significantly promoted astrocyte proliferation as measured by Trypan Blue, DRAQ5 and 5-ethynyl-2’-deoxyuridine (EdU) staining, but not 23 kDa FGF-2. Furthermore, our results demonstrated that AKT signaling pathway was required for the protective and proliferative effects of FGF-2. Downstream effector studies indicated that 17 kDa FGF-2 promoted astrocyte proliferation by enhanced expression of c-Myc, Cyclin D1, Cyclin E. Furthermore, our data suggested that Cyclin D1 was required for the proliferative effect of LMW FGF2 in astrocytes. Taken together, our findings provide important information for the similarities and differences between 23 kDa and17 kDa isoforms of FGF-2 on astrocyte survival and proliferation.

Neuronal Stem Cell and Drug Interactions: A Systematic Review and Meta-Analysis: Concise Review

Stem cell therapy is a promising treatment option for neurodegenerative diseases that mostly affect geriatric patients who often suffer from comorbidities requiring multiple medications. However, not much is known about the interactions between stem cells and drugs. Here, we focus on the potential interactions between drugs used to treat the comorbidities or sequelae of neurodegenerative diseases and neuronal stem cells to reveal potential effects on drug safety and efficacy. To determine the potential effects of drugs frequently used in geriatric patients (analgesic, antibiotic, antidepressant, antidiabetic, antihyperlipidemic, and antihypertensive drugs) on neuronal stem cell differentiation and proliferation, we systematically searched PubMed to identify nonreview articles published in English in peer-reviewed journals between January 1, 1991, and June 7, 2018. We identified 5,954 publications, of which 214 were included. Only 62 publications provided the complete data sets required for meta-analysis. We found that antidepressants stimulated neuronal stem cell proliferation but not differentiation under physiologic conditions and increased the proliferation of stem cells in the context of stress. Several other potential interactions were identified, but the limited number of available data sets precludes robust conclusions. Although available data were in most cases insufficient to perform robust meta-analysis, a clear interaction between antidepressants and neuronal stem cells was identified. We reveal other potential interactions requiring further experimental investigation. We recommend that future research addresses such interactions and investigates the best combination of pharmacological interventions and neuronal stem cell treatments for more efficient and safer patient care. Stem Cells Translational Medicine 2019;8:1202-1211.

Dysregulation of Fibroblast Growth Factor 10 in the Peripheral Blood of Patients with Schizophrenia

The fibroblast growth factor (FGF) system has been suggested to be involved in the development of schizophrenia (SCZ). However, the potential roles of all FGFs have not been well studied in the literature. Here, we investigated the concentration of peripheral blood fibroblast 10 (FGF10) in patients with SCZ to determine whether FGF10 could serve as a biomarker for SCZ. We recruited 130 SCZ patients (57 first-episode, drug-free patients and 73 chronically medicated patients) and 111 healthy controls. Our results showed that serum FGF10 levels were significantly decreased in SCZ patients when compared with controls. Sub-group analyses revealed that both first-episode, drug-free patients and chronically medicated patients had lower levels of FGF10 than controls. Moreover, both male and female SCZ patients had significantly decreased blood FGF10 levels relative to control subjects. Using a receiver operating characteristic curve, the optimal cutoff value of FGF10 level as an indicator for diagnosis of first-onset SCZ patients was projected to be 152.3 pg/ml, which yielded a sensitivity of 0.658 and specificity of 0.649, with an area under the curve of 0.665 (95% confidence interval, 0.577-0.754). Taken together, our results are the first to demonstrate an association between FGF10 and SCZ, providing further evidence for the neurotrophic factor hypothesis of SCZ.

Neurotrophic, Gene Regulation, and Cognitive Functions of Carboxypeptidase E-Neurotrophic Factor-α1 and Its Variants

Carboxypeptidase E, also known as neurotrophic factor-α1 (CPE-NFα1), was first discovered as an exopeptidase and is known to work by cleaving C-terminal basic amino acids from prohormone intermediates to produce mature peptide hormones and neuropeptides in the endocrine and central nervous systems, respectively. CPE-NFα1 also plays a critical role in prohormone sorting and secretory vesicle transportation. Recently, emerging studies have indicated that CPE-NFα1 exerts multiple non-enzymatic physiological roles in maintaining normal central nervous system function and in neurodevelopment. This includes potent neuroprotective and anti-depressant activities, as well as stem cell differentiation functions. In addition, N-terminal truncated variants of CPE-NFα1 have been identified to regulate expression of important neurodevelopmental genes. This mini-review summarizes recent advances in understanding the mechanisms underlying CPE-NFα1’s function in neuroprotection during stress and aspects of neurodevelopment.

Insulin Resistance as a Shared Pathogenic Mechanism Between Depression and Type 2 Diabetes

Neuropsychiatric disorders and type 2 diabetes (T2D) are major public health concerns proposed to be intimately connected. T2D is associated with increased risk of dementia, neuropsychiatric and mood disorders. Evidences of the involvement of insulin signaling on brain mechanisms related to depression indicate that insulin resistance, a hallmark of type 2 diabetes, could develop in the brains of depressive patients. In this article, we briefly review possible molecular mechanisms associating defective brain insulin signaling with reward system, neurogenesis, synaptic plasticity and hypothalamic-pituitary-adrenal (HPA) stress axis in depression. We further discuss the involvement of tumor necrosis factor α (TNFα) promoting defective insulin signaling and depressive-like behavior in rodent models. Finally, due to the high resistant rate of anti-depressants, novel insights into the link between insulin resistance and depression may advance the development of alternative treatments for this disease.

2,3,5,4'-Tetrahydroxystilbene-2-O-beta-D-glucoside Reverses Stress-Induced Depression via Inflammatory and Oxidative Stress Pathways

Major depressive disorder (MDD) is a chronic mental disease that adversely affects human mood and cognition. Many first-line antidepressant drugs have high rates of partial responsiveness or nonresponsiveness with side effects, and finding more effective drugs for the treatment of depression is therefore urgently needed. THSG, a main active compound of the traditional Chinese herb Polygonum multiflorum, reportedly acts as a neuroprotective agent. This study aimed to illustrate whether THSG prevents depressive-like behaviors induced by chronic restraint stress (CRS) in an MDD mouse model. Our results demonstrated that the peripheral administration of different THSG doses (10 mg/kg, 20 mg/kg, and 40 mg/kg) reversed the depressive-like behaviors in CRS mice as measured by the tail suspension test, forced swimming test, and open-field test. Further analyses suggested that THSG treatment reduced oxidative stress in both the central and peripheral nervous systems of CRS mice. In addition, heightened inflammatory responses, demonstrated by the increased expression of proinflammatory factors (TNF-α, IL-1β, and IL-6), in hippocampal and prefrontal cortex tissues of CRS mice were inhibited by THSG administration. THSG also restored the diminished Akt signaling pathway in the brains of CRS mice. Moreover, our data suggest increased astrocyte proliferation and neurogenesis in the hippocampus of CRS mice after THSG treatment. Taken together, our results demonstrated an antidepressant effect of THSG in a mouse model of MDD for the first time, and oxidative stress and inflammatory pathways were determined to play roles in this effect.

Increased serum FGF2 levels in first-episode, drug-free patients with schizophrenia

Preclinical and clinical studies suggest that brain-derived neurotrophic factor and nerve growth factor are involved in the pathogenesis of schizophrenia (SCZ). However, the roles of other neurotrophic factors in SCZ remain unclear. The aim of this study was to investigate the blood levels of FGF2 and ADNP in first-episode, drug-free SCZ patients compared with healthy control subjects. 20 SCZ patients, and 20 age and sex matched controls were recruited in this study. Serum FGF2 and ADNP protein levels were measured by ELISA assay, and the results showed that FGF2 levels were significantly increased in patients with SCZ when compared with controls, whereas ADNP protein levels did not significantly associated with SCZ. However, we found that blood ADNP mRNA levels were significantly increased in the patients with SCZ when compared with controls. In addition, subgroup analyses suggested that FGF2 levels were significantly increased in female patients of SCZ, but not in male patients of SCZ. Correlation analyses suggested that age and disease severity (PANSS score) did not have moderating effects on the serum FGF2 levels. Taken together, our results for the first time demonstrated that blood FGF2 was up-regulated in first-episode, drug free-SCZ patients, therefore enhancing the knowledge of neurotrophic factor profile in patients with SCZ.

Cloning, gene regulation, and neuronal proliferation functions of novel N-terminal-truncated carboxypeptidase E/neurotrophic factor-αl variants in embryonic mouse brain

Carboxypeptidase E (CPE), an exopeptidase involved in proneuropeptide processing, is also a neurotrophic factor, named neurotrophic factor-α1 (NF-α1) and has important roles in neuroprotection, stem cell differentiation, and neurite outgrowth, independent of enzymatic activity. Additionally, an N-terminal-truncated CPE/NF-α1 variant, (CPE/NF-α1)-ΔN, proposed from bioinformatic analysis of GenBank (National Center for Biotechnology Information, Bethesda, MD, USA) DNA sequences and encoding a 40-kDa protein, has been found to be exclusively expressed in embryonic neurons. To investigate the function of (CPE/NF-α1)-ΔN in neurodevelopment, we first cloned (CPE/NF-α1)-ΔN transcripts from an embryonic mouse brain. A rapid amplification of cDNA ends assay, DNA sequencing, and Northern blot revealed 1.9- and 1.73-kb transcripts, which encoded 47- and 40-kDa (CPE/NF-α1)-ΔN proteins, respectively. Those proteins were expressed in embryonic mouse brain. Expression of the 2 (CPE/NF-α1)-ΔN mRNAs surged at embryonic d 10.5, correlating with the time of neurogenesis in the developing brain and also at postnatal d 1. HT22 cells, a mouse hippocampal cell line, transduced with 40 kDa (CPE/NF-α1)-ΔN up-regulated expression of genes involved in embryonic neurodevelopment: insulin-like growth factor binding protein 2 ( IGFBP2), death-associated protein 1, and ephrin A1, which regulate proliferation, programmed cell death, and neuronal migration, respectively. HT22 cells and embryonic cortical neurons overexpressing 40 kDa (CPE/NF-α1)-ΔN exhibited enhanced proliferation, which was inhibited by IGFBP2 short interfering RNA treatment. Thus, 40 kDa (CPE/NF-α1)-ΔN has an important, enzymatically independent role in the regulation of genes critical for neurodevelopment.-Xiao, L., Yang, X., Sharma, V. K., Loh, Y. P. Cloning, gene regulation, and neuronal proliferation functions of novel N-terminal-truncated carboxypeptidase E/neurotrophic factor-αl variants in embryonic mouse brain.

Insulin resistance, an unmasked culprit in depressive disorders: Promises for interventions

Depressive disorders constitute a set of debilitating diseases with psychological, societal, economic and humanitarian consequences for millions of people worldwide. Scientists are beginning to understand the reciprocal communication between the brain and the rest of the body in the etiology of these diseases. In particular, scientists have noted a connection between depressive disorders, which are primarily seen as brain-based, and, insulin resistance (IR), a modifiable metabolic inflammatory state that is typically seen as peripheral. We highlight evidence showing how treating IR, with drugs or behavioral interventions, may ameliorate or possibly prevent, depressive disorders and their long-term consequences at various stages of the life course. This article is part of the Special Issue entitled 'Metabolic Impairment as Risk Factors for Neurodegenerative Disorders.'

Nuclear deterrents: Intrinsic regulators of IL-1β-induced effects on hippocampal neurogenesis

Hippocampal neurogenesis, the process by which new neurons are born and develop into the host circuitry, begins during embryonic development and persists throughout adulthood. Over the last decade considerable insights have been made into the role of hippocampal neurogenesis in cognitive function and the cellular mechanisms behind this process. Additionally, an increasing amount of evidence exists on the impact of environmental factors, such as stress and neuroinflammation on hippocampal neurogenesis and subsequent impairments in cognition. Elevated expression of the pro-inflammatory cytokine interleukin-1β (IL-1β) in the hippocampus is established as a significant contributor to the neuronal demise evident in many neurological and psychiatric disorders and is now known to negatively regulate hippocampal neurogenesis. In order to prevent the deleterious effects of IL-1β on neurogenesis it is necessary to identify signalling pathways and regulators of neurogenesis within neural progenitor cells that can interact with IL-1β. Nuclear receptors are ligand regulated transcription factors that are involved in modulating a large number of cellular processes including neurogenesis. In this review we focus on the signalling mechanisms of specific nuclear receptors involved in regulating neurogenesis (glucocorticoid receptors, peroxisome proliferator activated receptors, estrogen receptors, and nuclear receptor subfamily 2 group E member 1 (NR2E1 or TLX)). We propose that these nuclear receptors could be targeted to inhibit neuroinflammatory signalling pathways associated with IL-1β. We discuss their potential to be therapeutic targets for neuroinflammatory disorders affecting hippocampal neurogenesis and associated cognitive function.

Rosiglitazone Exerts an Anti-depressive Effect in Unpredictable Chronic Mild-Stress-Induced Depressive Mice by Maintaining Essential Neuron Autophagy and Inhibiting Excessive Astrocytic Apoptosis

There is increasing interest in the association between depression and the development of metabolic diseases. Rosiglitazone, a therapeutic drug used to treat type 2 diabetes mellitus, has shown neuroprotective effects in patients with stroke and Alzheimer's disease. The present study was performed to evaluate the possible roles of rosiglitazone in in vivo (unpredictable chronic mild stress-induced depressive mouse model) and in vitro (corticosterone-induced cellular model) depressive models. The results showed that rosiglitazone reversed depressive behaviors in mice, as indicated by the forced swimming test and open field test. Rosiglitazone was also found to inhibit the inflammatory response, decrease corticosterone levels, and promote astrocyte proliferation and neuronal axon plasticity in the prefrontal cortex of mice. This series of in vivo and in vitro experiments showed that autophagy among neurons was inhibited in depressive models and that rosiglitazone promoted autophagy by upregulating LKB1, which exerted neuroprotective effects. Rosiglitazone was also found to activate the Akt/CREB pathway by increasing IGF-1R expression and IGF-1 protein levels, thereby playing an anti-apoptotic role in astrocytes. Rosiglitazone's autophagy promotion and neuroprotective effects were found to be reversed by the PPARγ antagonist T0070907 in primary neurons and by PPARγ knockdown in an N2a cell line. In conclusion, we found that rosiglitazone protects both neurons and astrocytes in in vivo and in vitro depressive models, thereby playing an anti-depressive role. These findings suggest that PPARγ could be a new target in the development of anti-depressive drugs.

Hippocampal bone morphogenetic protein signaling mediates behavioral effects of antidepressant treatment

Many antidepressants stimulate adult hippocampal neurogenesis, but the mechanisms by which they increase neurogenesis and modulate behavior are incompletely understood. Here we show that hippocampal bone morphogenetic protein (BMP) signaling is modulated by antidepressant treatment, and that the changes in BMP signaling mediate effects of antidepressant treatment on neural progenitor cell proliferation and behavior. Treatment with the selective serotonin reuptake inhibitor fluoxetine suppressed BMP signaling in the adult mouse hippocampus both by decreasing levels of BMP4 ligand and increasing production of the BMP inhibitor noggin. Increasing BMP signaling in the hippocampus via viral overexpression of BMP4 blocked the effects of fluoxetine on proliferation in the dentate gyrus and on depressive behavior. Conversely, inhibiting BMP signaling via viral overexpression of noggin in the hippocampus or infusion of noggin into the ventricles exerted antidepressant and anxiolytic activity along with an increase in hippocampal neurogenesis. Similarly, conditional genetic deletion of the type II BMP receptor in Ascl1-expressing cells promoted neurogenesis and reduced anxiety- and depression-like behaviors, suggesting that neural progenitor cells contribute to the effects of BMP signaling on affective behavior. These observations indicate that BMP signaling in the hippocampus regulates depressive behavior, and that decreasing BMP signaling may be required for the effects of some antidepressants. Thus BMP signaling is a new and powerful potential target for the treatment of depression.

Effects of [Nphe1, Arg14, Lys15] N/OFQ-NH2 (UFP-101), a potent NOP receptor antagonist, on molecular, cellular and behavioural alterations associated with chronic mild stress

The present study investigated the effect of [Nphe¹] Arg¹⁴, Lys¹⁵-N/OFQ-NH₂ (UFP-101), a selective NOP receptor antagonist, in chronic mild stress (CMS) in male Wistar rats. NOP receptor antagonists were reported to elicit antidepressant-like effects in rodents. Our aim was to investigate UFP-101 effects on CMS-induced anhedonia and impairment of hippocampal neurogenesis. UFP-101 (10 nmol/rat intracerebroventricularly) did not influence sucrose intake in non-stressed animals, but reinstated basal sucrose consumption in stressed animals from the second week of treatment. UFP-101 also reversed stress effects in forced swimming test and in open field. Fluoxetine (10 mg/kg intraperitoneally) produced similar effects. Moreover, we investigated whether UFP-101 could affect CMS-induced impairment in hippocampal cell proliferation and neurogenesis, and in fibroblast growth factor (FGF-2) expression. Our data confirm that CMS reduced neural stem cell proliferation and neurogenesis in adult rat hippocampus. Chronic UFP-101 treatment did not affect the reduced proliferation (bromodeoxyuridine-positive cells) observed in stressed animals. However, UFP-101 increased the number of doublecortin-positive cells, restoring neurogenesis. Finally, UFP-101 significantly increased FGF-2 expression, reduced by CMS. These findings support the view that blockade of NOP receptors produces antidepressant-like effects in CMS associated with positive effects on neurogenesis and FGF-2 expression. Therefore, NOP receptors may represent a target for innovative antidepressant drugs.

Safety and tolerability of adjunctive rosiglitazone treatment for children with uncomplicated malaria

BACKGROUND

Despite the widespread use and availability of rapidly acting anti-malarials, the fatality rate of severe malaria in sub-Saharan Africa remains high. Adjunctive therapies that target the host response to malaria infection may further decrease mortality over that of anti-malarial agents alone. Peroxisome proliferator-activated receptor-gamma agonists (e.g. rosiglitazone) have been shown to act on several pathways implicated in the pathogenesis of severe malaria and may improve clinical outcome as an adjunctive intervention.

METHODS

In this study, the safety and tolerability of adjunctive rosiglitazone in paediatric uncomplicated malaria infection was evaluated in Mozambique, as a prelude to its evaluation in a randomized controlled trial in paediatric severe malaria. The study was a prospective, randomized, double-blind, placebo-controlled, phase IIa trial of rosiglitazone (0.045 mg/kg/dose) twice daily for 4 days versus placebo as adjunctive treatment in addition to Mozambican standard of care (artemisinin combination therapy Coartem^®) in children with uncomplicated malaria. The primary outcomes were tolerability and safety, including clinical, haematological, biochemical, and electrocardiographic evaluations.

RESULTS

Thirty children were enrolled: 20 were assigned to rosiglitazone and 10 to placebo. Rosiglitazone treatment did not induce hypoglycaemia nor significantly alter clinical, biochemical, haematological, or electrocardiographic parameters.

CONCLUSIONS

Adjunctive rosiglitazone was safe and well-tolerated in children with uncomplicated malaria, permitting the extension of its evaluation as adjunctive therapy for severe malaria. The trial is registered with Clinicaltrials.gov, NCT02694874.

Absence of Carboxypeptidase E/Neurotrophic Factor-Α1 in Knock-Out Mice Leads to Dysfunction of BDNF-TRKB Signaling in Hippocampus

Carboxypeptidase E (CPE), first discovered as a prohormone processing enzyme, has also now been shown to be a secreted neurotrophic factor (neurotrophic factor-α1, NF-α1) that acts extracellularly as a signaling molecule to mediate neuroprotection, cortical stem cell differentiation, and antidepressive-like behavior in mice. Since brain-derived neurotrophic factor (BDNF) has very similar trophic functions, and its processing from pro-BDNF involves intracellular sorting of pro-BDNF to the regulated secretory pathway by CPE acting as a sorting receptor, we investigated whether the lack of CPE/NF-α1 would affect BDNF-TrkB signaling in mice. Previous studies have shown that CPE/NF-α1 knock-out (KO) mice exhibited severe neurodegeneration of the hippocampal CA3 region which raises the question of why other neurotrophic factors such as BDNF could not compensate for the deficiency of CPE. Here, we show that the expressions of pro-BDNF mRNA and protein in hippocampus of CPE-KO mice were similar to WT mice, but mature BDNF was ∼40% less in the CPE-KO mice, suggesting decreased intracellular processing of pro-BDNF. Furthermore, TrkB receptor levels were similar in both genotypes, but there was significantly decreased phosphorylation of TrkB receptor in the CPE-KO mice. Electrophysiological studies showed lack of formation of long-term potentiation in hippocampal slices of CPE-KO mice compared to WT mice, which was not rescued by application of BDNF, indicating dysfunction of the BDNF-TrkB signaling system. The CPE-KO mice showed normal postsynaptic AMPA response to kainate application in hippocampal slices and dissociated neurons. Our findings indicate that CPE/NF-α1 is essential for normal BDNF-TrkB signaling function in mouse hippocampus.

A Novel Single Nucleotide T980C Polymorphism in the Human Carboxypeptidase E Gene Results in Loss of Neuroprotective Function

Report of a human with a homozygous truncating null mutation of the Carboxypeptidase E (CPE) gene with endocrinological and neurological deficits prompted us to search for other mutations in the human CPE gene that might be linked to disease. We searched an EST database and identified from a small population of patients, a novel T to C single nucleotide polymorphism (SNP) in the CPE gene at bp980 of exon 4, herein called TC-CPE. This introduces a tryptophan to arginine (W235R) mutation in the catalytic domain of human CPE protein. Over-expression of TC-CPE in N2A cells, a neuroendocrine cell line, showed that it was synthesized, but was found in lesser amounts compared to over-expressed WT-CPE in these cells. Furthermore, TC-CPE was secreted poorly from these N2A cells. The levels of TC-CPE were significantly increased after the N2A cells were treated with MG132 (a proteasome inhibitor), suggesting that TC-CPE was targeted to proteasomes for degradation in N2A cells. In addition, TC-CPE induced ER stress as demonstrated by the increased expression of CHOP in N2A cells. Double labeling of CPE and calnexin (and ER marker) suggested the accumulation of TC-CPE in the ER, and the accumulation appears to be enhanced by the treatment of MG132 in the cells. Moreover, the secreted levels of TC-CPE were not affected by the treatment of MG132 in the cells. Over-expression studies revealed that while N2A cells transfected with WT-CPE showed reduced cytotoxicity when challenged with H₂O₂ compared to cells expressing an empty vector, cells transfected with TC-CPE had no effect. Furthermore, WT-CPE condition medium showed protective effect against oxidative stress, but not TC-CPE condition medium. Although co-expression of WT-CPE and TC-CPE in N2A cells resulted in the reduction in secretion of WT-CPE, co-expression of WT-CPE and TC-CPE did not significantly affect the protective effect of WT-CPE. Taken together, we have identified a novel SNP in the CPE gene which results in the loss of its neuroprotective function in cells and may confer neurological disorders in humans.

Neuroserpin Attenuates H2O2-Induced Oxidative Stress in Hippocampal Neurons via AKT and BCL-2 Signaling Pathways

Oxidative stress plays a critical role in neuronal injury and is associated with various neurological diseases. Here, we explored the potential protective effect of neuroserpin against oxidative stress in primary cultured hippocampal neurons. Our results show that neuroserpin inhibits H2O2-induced neurotoxicity in hippocampal cultures as measured by WST, LDH release, and TUNEL assays. We found that neuroserpin enhanced the activation of AKT in cultures subjected to oxidative stress and that the AKT inhibitor Ly294002 blocked this neuroprotective effect. Neuroserpin increased the expression of the anti-apoptotic protein BCL-2 and blocked the activation of caspase-3. Neuroserpin did not increase the level of neuroprotection over levels seen in neurons transduced with a BCL-2 expression vector, and an inhibitor of Trk receptors, K252a, did not block neuroserpin's effect. Taken together, our study demonstrates that neuroserpin protects against oxidative stress-induced dysfunction and death of primary cultured hippocampal neurons through the AKT-BCL-2 signaling pathway through a mechanism that does not involve the Trk receptors and leads to inhibition of caspase-3 activation.