FLUOXETINE modifies the expression of serotonergic markers in a differentiation-dependent fashion in the mesencephalic neural cell line A1 mes c-myc

Generation of High-Yield, Functional Oligodendrocytes from a c-myc Immortalized Neural Cell Line, Endowed with Staminal Properties

Neural stem cells represent a powerful tool to study molecules involved in pathophysiology of Nervous System and to discover new drugs. Although they can be cultured and expanded in vitro as a primary culture, their use is hampered by their heterogeneity and by the cost and time needed for their preparation. Here we report that mes-c-myc A1 cells (A1), a neural cell line, is endowed with staminal properties. Undifferentiated/proliferating and differentiated/non-proliferating A1 cells are able to generate neurospheres (Ns) in which gene expression parallels the original differentiation status. In fact, Ns derived from undifferentiated A1 cells express higher levels of Nestin, Kruppel-like factor 4 (Klf4) and glial fibrillary protein (GFAP), markers of stemness, while those obtained from differentiated A1 cells show higher levels of the neuronal marker beta III tubulin. Interestingly, Ns differentiation, by Epidermal Growth Factors (EGF) and Fibroblast Growth Factor 2 (bFGF) withdrawal, generates oligodendrocytes at high-yield as shown by the expression of markers, Galactosylceramidase (Gal-C) Neuron-Glial antigen 2 (NG2), Receptor-Interacting Protein (RIP) and Myelin Basic Protein (MBP). Finally, upon co-culture, Ns-A1-derived oligodendrocytes cause a redistribution of contactin-associated protein (Caspr/paranodin) protein on neuronal cells, as primary oligodendrocytes cultures, suggesting that they are able to form compact myelin. Thus, Ns-A1-derived oligodendrocytes may represent a time-saving and low-cost tool to study the pathophysiology of oligodendrocytes and to test new drugs.

Neurotrophic Factor BDNF, Physiological Functions and Therapeutic Potential in Depression, Neurodegeneration and Brain Cancer

Brain-derived neurotrophic factor (BDNF) is one of the most distributed and extensively studied neurotrophins in the mammalian brain. BDNF signals through the tropomycin receptor kinase B (TrkB) and the low affinity p75 neurotrophin receptor (p75NTR). BDNF plays an important role in proper growth, development, and plasticity of glutamatergic and GABAergic synapses and through modulation of neuronal differentiation, it influences serotonergic and dopaminergic neurotransmission. BDNF acts as paracrine and autocrine factor, on both pre-synaptic and post-synaptic target sites. It is crucial in the transformation of synaptic activity into long-term synaptic memories. BDNF is considered an instructive mediator of functional and structural plasticity in the central nervous system (CNS), influencing dendritic spines and, at least in the hippocampus, the adult neurogenesis. Changes in the rate of adult neurogenesis and in spine density can influence several forms of learning and memory and can contribute to depression-like behaviors. The possible roles of BDNF in neuronal plasticity highlighted in this review focus on the effect of antidepressant therapies on BDNF-mediated plasticity. Moreover, we will review data that illustrate the role of BDNF as a potent protective factor that is able to confer protection against neurodegeneration, in particular in Alzheimer's disease. Finally, we will give evidence of how the involvement of BDNF in the pathogenesis of brain glioblastoma has emerged, thus opening new avenues for the treatment of this deadly cancer.

Ruta graveolens as a potential source of neuroactive compounds to promote and restore neural functions

Nutraceuticals had always been known for their therapeutic effects in ancient medicine and had been the primary healing remedy until the introduction of modern chemistry and pharmacology. However, their use has not been dismissed but actually is acquiring a new acclamation among the scientific community especially for their efficacy on the Central Nervous System (CNS). Molecular mechanisms of the most common neurodegenerative diseases are now being uncovered and along with that the molecules that drive the neurodegenerative processes. It is not surprising that some natural compounds can interact with those molecules and interfere with the pathological pathways halting the cascades that ultimately lead to neuronal cell death. The plant Ruta graveolens has gained increased attention in medicinal chemistry due to its beneficial role to treat a variety of human diseases and also because of the presence of a huge number of compounds belonging to different classes of natural products, including neuroactive compounds potentially able to promote neuroprotection. Among all the components of the plant extract, rutin – which is highly, if not the most, abundant – positively interacts with the neurophysiology of the CNS too, being particularly efficient against neurotoxicity. Rutin, has proven to be protective in a variety of experimental settings of neurodegeneration. Finally, it has been shown that the water extract of Ruta graveolens (RGWE) induces death of glioblastoma cells but not of neuronal cells. Moreover, it also fosters cell cycle re-entry and differentiation of neuronal cells. This peculiarity represents a promising tool to promote neural plasticity in pathological conditions.

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Traditional therapeutic use of the plant Ruta graveolens in a large variety of illnesses.

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It has been used, together with its main component rutin to treat some neurodegenerative diseases.

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It might own compounds able to foster plasticity in neural cells.

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It is able to kill neural cancer cells but not neurons.

A targeted secretome profiling by multiplexed immunoassay revealed that secreted chemokine ligand 2 (MCP-1/CCL2) affects neural differentiation in mesencephalic neural progenitor cells

Chemokines and cytokines, primarily known for their roles in the immune and inflammatory response, have also been identified as key components of the neurogenic niche where they are involved in the modulation of neural stem cell proliferation and differentiation. However, a complete understanding of the functional role played in neural differentiation and a comprehensive profiling of these secreted molecules are lacking. By exploiting the multiplexing capability of magnetic bead-based immunoassays, we have investigated the changes of the expression levels of a set of chemokines and cytokines released from the pluripotent neural cell line mes-c-myc A1 following its differentiation from a proliferating phenotype (A1P) toward a neural (A1D) phenotype. We found a subset of molecules exclusively released from A1P, whereas others were differentially detected in A1P and A1D conditioned media. Among them, we identified monocyte chemoattractant protein-1/chemokine ligand 2 (MCP-1/CCL2) as a proneurogenic factor able to affect neuronal differentiation of A1 cells as well as of neuroblasts from primary cultures and to induce the elongation and/or formation of neuritic processes. Altogether, data are suggestive of a main role played by the CCL2/CCR2 signaling pathway and in general of the network of secreted cytokines/chemokines in the differentiation of neural progenitor cells toward a neural fate.

Secretome profiling of differentiated neural mes-c-myc A1 cell line endowed with stem cell properties

Neural stem cell proliferation and differentiation play a crucial role in the formation and wiring of neuronal connections forming neuronal circuits. During neural tissues development, a large diversity of neuronal phenotypes is produced from neural precursor cells. In recent years, the cellular and molecular mechanisms by which specific types of neurons are generated have been explored with the aim to elucidate the complex events leading to the generation of different phenotypes via distinctive developmental programs that control self-renewal, differentiation, and plasticity. The extracellular environment is thought to provide instructive influences that actively induce the production of specific neuronal phenotypes. In this work, the secretome profiling of differentiated neural mes-c-myc A1 (A1) cell line endowed with stem cell properties was analyzed by applying a shotgun LC-MS/MS approach. The results provide a list of secreted molecules with potential relevance for the functional and biological features characterizing the A1 neuronal phenotype. Proteins involved in biological processes closely related to nervous system development including neurites growth, differentiation of neurons and axonogenesis were identified. Among them, proteins belonging to extracellular matrix and cell-adhesion complexes as well as soluble factors with well established neurotrophic properties were detected. The presented work provides the basis to clarify the complex extracellular protein networks implicated in neuronal differentiation and in the acquisition of the neuronal phenotype. This article is part of a Special Issue entitled: An Updated Secretome.

Tryptophan hydroxylase 2 (TPH2) in a neuronal cell line: modulation by cell differentiation and NRSF/rest activity

Serotonin (5-HT) is a neurotransmitter involved in many aspects of the neuronal function. The synthesis of 5-HT is initiated by the hydroxylation of tryptophan, catalyzed by tryptophan hydroxylase (TPH). Two isoforms of TPH (TPH1 and TPH2) have been identified, with TPH2 almost exclusively expressed in the brain. Following TPH2 discovery, it was reported that polymorphisms of both gene and non-coding regions are associated with a spectrum of psychiatric disorders. Thus, insights into the mechanisms that specifically regulate TPH2 expression and its modulation by exogenous stimuli may represent a new therapeutic approach to modify serotonergic neurotransmission. To this aim, a CNS-originated cell line expressing TPH2 endogenously represents a valid model system. In this study, we report that TPH2 transcript and protein are modulated by neuronal differentiation in the cell line A1 mes-c-myc (A1). Moreover, we show luciferase activity driven by the human TPH2 promoter region and demonstrate that upon mutation of the NRSF/REST responsive element, the promoter activity strongly increases with cell differentiation. Our data suggest that A1 cells could represent a model system, allowing an insight into the mechanisms of regulation of TPH2 and to identify novel therapeutic targets in the development of drugs for the management of psychiatric disorders.

The genetics of selective serotonin reuptake inhibitors

Selective serotonin reuptake inhibitors (SSRIs) are among the most widely prescribed drugs in psychiatry. Based on the fact that SSRIs increase extracellular monoamine levels in the brain, the monoamine hypothesis of depression was introduced, postulating that depression is associated with too low serotonin, dopamine and noradrenaline levels. However, several lines of evidence indicate that this hypothesis is too simplistic and that depression and the efficacy of SSRIs are dependent on neuroplastic changes mediated by changes in gene expression. Because a coherent view on global gene expression is lacking, we aim to provide an overview of the effects of SSRI treatment on the final targets of 5-HT receptor signal transduction pathways, namely the transcriptional regulation of genes. We address gene polymorphisms in humans that affect SSRI efficacy, as well as in vitro studies employing human-derived cells. We also discuss the molecular targets affected by SSRIs in animal models, both in vivo and in vitro. We conclude that serotonin transporter gene variation in humans affects the efficacy and side-effects of SSRIs, whereas SSRIs generally do not affect serotonin transporter gene expression in animals. Instead, SSRIs alter mRNA levels of genes encoding serotonin receptors, components of non-serotonergic neurotransmitter systems, neurotrophic factors, hypothalamic hormones and inflammatory factors. So far little is known about the epigenetic and age-dependent molecular effects of SSRIs, which might give more insights in the working mechanism(s) of SSRIs.

Advances in tryptophan hydroxylase-2 gene expression regulation: new insights into serotonin-stress interaction and clinical implications

Serotonin (5-HT) modulates the stress response by interacting with the hormonal hypothalamic-pituitary-adrenal (HPA) axis and neuronal sympathetic nervous system (SNS). Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in 5-HT biosynthesis, and the recent identification of a second, neuron-specific TPH isoform (TPH2) opened up a new area of research. While TPH2 genetic variance has been linked to numerous behavioral traits and disorders, findings on TPH2 gene expression have not only reinforced, but also provided new insights into, the long-recognized but not yet fully understood 5-HT-stress interaction. In this review, we summarize advances in TPH2 expression regulation and its relevance to the stress response and clinical implications. Particularly, based on findings on rhesus monkey TPH2 genetics and other relevant literature, we propose that: (i) upon activation of adrenal cortisol secretion, the cortisol surge induces TPH2 expression and de novo 5-HT synthesis; (ii) the induced 5-HT in turn inhibits cortisol secretion by modulating the adrenal sensitivity to ACTH via the suprachiasmatic nuclei (SCN)-SNS-adrenal system, such that it contributes to the feedback inhibition of cortisol production; (iii) basal TPH2 expression or 5-HT synthesis, as well as early-life experience, influence basal cortisol primarily via the hormonal HPA axis; and (iv) 5'- and 3'-regulatory polymorphisms of TPH2 may differentially influence the stress response, presumably due to their differential roles in gene expression regulation. Our increasing knowledge of TPH2 expression regulation not only helps us better understand the 5-HT-stress interaction and the pathophysiology of neuropsychiatric disorders, but also provides new strategies for the treatment of stress-associated diseases.

Quantitative neuroproteomics: classical and novel tools for studying neural differentiation and function

Mechanisms underlying neural stem cell proliferation, differentiation and maturation play a critical role in the formation and wiring of neuronal connections. This process involves the activation of multiple serial events, which guide the undifferentiated cells to different lineages via distinctive developmental programs, forming neuronal circuits and thus shaping the adult nervous system. Furthermore, alterations within these strictly regulated pathways can lead to severe neurological and psychiatric diseases. In this framework, the investigation of the high dynamic protein expression changes and other factors affecting protein functions, for example post-translational modifications, the alterations of protein interaction networks, is of pivotal importance for the understanding of the molecular mechanisms responsible for cell differentiation. More recently, proteomic studies in neuroscience ("neuroproteomics") are receiving increased interest for the primary understanding of the regulatory networks underlying neuronal differentiation processes. Besides the classical two-dimensional-based proteomic strategies, the emerging platforms for LC-MS shotgun proteomic analysis hold great promise in unraveling the molecular basis of neural stem cell differentiation. In this review, recent advancements in label-free LC-MS quantitative neuroproteomics are highlighted as a new tool for the study of neural differentiation and functions, in comparison to mass spectrometry-based labeling approaches. The more commonly used protein profiling strategies and model systems for the analysis of neural differentiation are also discussed, along with the challenging proteomic approaches aimed to analyze the nervous system-specific organelles, the neural cells secretome and the specific protein interaction networks.

Association of a functional polymorphism in the adrenomedullin gene (ADM) with response to paroxetine

To identify genes that may be relevant to the molecular action of antidepressants, we investigated transcriptional changes induced by the selective serotonin reuptake inhibitor paroxetine in a serotonergic cell line. We examined gene expression changes after acute treatment with paroxetine and sought to validate microarray results by quantitative PCR (qPCR). Concordant transcriptional changes were confirmed for 14 genes by qPCR and five of these, including the adrenomedullin gene (Adm), either approached or reached statistical significance. Reporter gene assays showed that a SNP (rs11042725) in the upstream flanking region of ADM significantly altered expression. Association analysis demonstrated rs11042725 to be significantly associated with response to paroxetine (odds ratio=0.075, P<0.001) but not with response to either fluoxetine or citalopram. Our results suggest that ADM is involved with the therapeutic efficacy of paroxetine, which may have pharmacogenetic utility.

Expression and association analyses of promoter variants of the neurogenic gene HES6, a candidate gene for mood disorder susceptibility and antidepressant response

Hes6 is a neurogenic gene which is down-regulated in the hippocampi of rats chronically treated with the antidepressant paroxetine. To assess whether variability in HES6 associates with mood disorder diagnosis or antidepressant response, this gene was sequenced in 24 unrelated New Zealand Caucasians. A total of 12 polymorphisms were identified, six of which were in the promoter region of the gene. Haplotypes encompassing the promoter SNPs were studied by cloning the region upstream of the transcription start site, and examining basal transcription rates in luciferase reporter gene assays. SNPs located at positions -1099, -831, -424 and -267 were shown to significantly alter expression of the reporter gene. These four variants were tested for association with mood disorder diagnosis or antidepressant response in a family study of depression, but no significant associations were observed. However, given the importance of this gene in neural function and development, the promoter variants described here may be of wider relevance.

Fluoxetine mediates G0/G1 arrest by inducing functional inhibition of cyclin dependent kinase subunit (CKS)1

Fluoxetine, a well-known antidepressant used clinically for mental depression has gained attention in cancer research owing to its chemosensitizing potential in drug resistant cell lines. Some preliminary reports, however, suggested its independent cytotoxic potential which is not yet well characterized. Our aim in this study was to characterize its antiproliferative activity in tumor cells and to further elucidate the mechanism. We found that fluoxetine sensitized the effect of cyclophosphamide even in drug sensitive MDA MB 231 and SiHa cells. IC(50) values of 28 and 32 microM were obtained for fluoxetine mediated antiproliferative response in these cells. Further, PARP and caspase 3 cleavage analyses confirmed fluoxetine mediated apoptosis at molecular level. Cell cycle analysis showed that fluoxetine arrested cells at G0/G1 phase in a time dependent manner. The application of bioinformatics tools at this juncture predicted CKS1 as one of the possible targets of fluoxetine, which is of relevance to cell cycle biology. Fluoxetine showed the potential to disrupt skp2-CKS1 assembly required for ubiquitination and proteasomal degradation of p27 and p21. Our in vitro results were in agreement with the predictions made in silico. We found that fluoxetine treatment could accumulate p27 and p21, an immediate outcome characteristic of functional inhibition of CKS1. This was accompanied by the accumulation of cyclin E, another possible target of CKS1. We observed CKS1 downregulation also upon prolonged fluoxetine treatment. Fluoxetine had downregulated cyclin A which confirmed G0/G1 arrest at the molecular level. We conclude that fluoxetine induced cell cycle arrest is CKS1 dependent.