Antidepressant Administration Modulates Neural Stem Cell Survival and Serotoninergic Differentiation Through Bcl-2

Psilocybin for dementia prevention? The potential role of psilocybin to alter mechanisms associated with major depression and neurodegenerative diseases

Major depression is an established risk factor for subsequent dementia, and depression in late life may also represent a prodromal state of dementia. Considering current challenges in the clinical development of disease modifying therapies for dementia, the focus of research is shifting towards prevention and modification of risk factors to alter the neurodegenerative disease trajectory. Understanding mechanistic commonalities underlying affective symptoms and cognitive decline may reveal biomarkers to aid early identification of those at risk of progressing to dementia during the preclinical phase of disease, thus allowing for timely intervention. Adult hippocampal neurogenesis (AHN) is a phenomenon that describes the birth of new neurons in the dentate gyrus throughout life and it is associated with spatial learning, memory and mood regulation. Microglia are innate immune system macrophages in the central nervous system that carefully regulate AHN via multiple mechanisms. Disruption in AHN is associated with both dementia and major depression and microgliosis is a hallmark of several neurodegenerative diseases. Emerging evidence suggests that psychedelics promote neuroplasticity, including neurogenesis, and may also be immunomodulatory. In this context, psilocybin, a serotonergic agonist with rapid-acting antidepressant properties has the potential to ameliorate intersecting pathophysiological processes relevant for both major depression and neurodegenerative diseases. In this narrative review, we focus on the evidence base for the effects of psilocybin on adult hippocampal neurogenesis and microglial form and function; which may suggest that psilocybin has the potential to modulate multiple mechanisms of action, and may have implications in altering the progression from major depression to dementia in those at risk.

Roles of microglia in adult hippocampal neurogenesis in depression and their therapeutics

Adult hippocampal neurogenesis generates functional neurons from neural progenitor cells in the hippocampal dentate gyrus (DG) to complement and repair neurons and neural circuits, thus benefiting the treatment of depression. Increasing evidence has shown that aberrant microglial activity can disrupt the appropriate formation and development of functional properties of neurogenesis, which will play a crucial role in the occurrence and development of depression. However, the mechanisms of the crosstalk between microglia and adult hippocampal neurogenesis in depression are not yet fully understood. Therefore, in this review, we first introduce recent discoveries regarding the roles of microglia and adult hippocampal neurogenesis in the etiology of depression. Then, we systematically discuss the possible mechanisms of how microglia regulate adult hippocampal neurogenesis in depression according to recent studies, which involve toll-like receptors, microglial polarization, fractalkine-C-X3-C motif chemokine receptor 1, hypothalamic-pituitary-adrenal axis, cytokines, brain-derived neurotrophic factor, and the microbiota-gut-brain axis, etc. In addition, we summarize the promising drugs that could improve the adult hippocampal neurogenesis by regulating the microglia. These findings will help us understand the complicated pathological mechanisms of depression and shed light on the development of new treatment strategies for this disease.

N-3 polyunsaturated fatty acids promote astrocyte differentiation and neurotrophin production independent of cAMP in patient-derived neural stem cells

Evidence from epidemiological and laboratory studies, as well as randomized placebo-controlled trials, suggests supplementation with n-3 polyunsaturated fatty acids (PUFAs) may be efficacious for treatment of major depressive disorder (MDD). The mechanisms underlying n-3 PUFAs potential therapeutic properties remain unknown. There are suggestions in the literature that glial hypofunction is associated with depressive symptoms and that antidepressants may normalize glial function. In this study, induced pluripotent stem cells (iPSC)-derived neuronal stem cell lines were generated from individuals with MDD. Astrocytes differentiated from patient-derived neuronal stem cells (iNSCs) were verified by GFAP. Cells were treated with eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or stearic acid (SA). During astrocyte differentiation, we found that n-3 PUFAs increased GFAP expression and GFAP positive cell formation. BDNF and GDNF production were increased in the astrocytes derived from patients subsequent to n-3 PUFA treatment. Stearic Acid (SA) treatment did not have this effect. CREB activity (phosphorylated CREB) was also increased by DHA and EPA but not by SA. Furthermore, when these astrocytes were treated with n-3 PUFAs, the cAMP antagonist, RP-cAMPs did not block n-3 PUFA CREB activation. However, the CREB specific inhibitor (666-15) diminished BDNF and GDNF production induced by n-3 PUFA, suggesting CREB dependence. Together, these results suggested that n-3 PUFAs facilitate astrocyte differentiation, and may mimic effects of some antidepressants by increasing production of neurotrophic factors. The CREB-dependence and cAMP independence of this process suggests a manner in which n-3 PUFA could augment antidepressant effects. These data also suggest a role for astrocytes in both MDD and antidepressant action.

Antidepressants Promote and Prevent Cancers

The review states that antidepressants (ADs) increase brain-derived neurotrophic factor (BDNF) transmission concomitantly in the brain and the blood: ADs increasing BDNF synthesis in specific areas of the central nervous system (CNS) could presumably affect megakaryocyte's production of platelets. ADs increase BDNF levels in the CNS and improve mood. In the blood, ADs increase BDNF release from platelets. The hypothesis presented here is that the release of BDNF from platelets contributes to the ADs effects on neurogenesis and on tumor growth in the cancer disease. Oncological studies indicate that chemicals ADs exert an aggravating effect on the cancer disease, possibly by promoting proplatelets formation and enhancing BDNF release from platelets in the tumor.

Subchronic administration of creatine produces antidepressant-like effect by modulating hippocampal signaling pathway mediated by FNDC5/BDNF/Akt in mice

Creatine has been shown to play a significant role in the pathophysiology and treatment of major depressive disorder (MDD) in preclinical and clinical studies. However, the biological mechanisms underlying its antidepressant effect is still not fully elucidated. This study investigated the effect of creatine (p.o.) administered for 21 days in the behavior of mice submitted to tail suspension test (TST), a predictive test of antidepressant activity. Creatine reduced the immobility time in the TST (1-10 mg/kg), without affecting locomotor activity, a finding consistent with an antidepressant profile. Creatine administration increased the ubiquitous creatine kinase (uCK) and creatine kinase brain isoform (CK-B) mRNA in the hippocampus of mice. Taking into account that PGC-1α induces FNDC5/irisin expression mediating BDNF-dependent neuroplasticity, the effect of creatine administration (1 mg/kg, p. o.) on the hippocampal PGC-1α, FNDC5 and BDNF gene expression was investigated. Creatine treatment increased PGC-1α, FNDC5 and BDNF mRNA in the hippocampus as well as BDNF immunocontent. The involvement of BDNF downstream intracellular signaling pathway mediated by Akt, proapoptotic proteins BAX and BAD and antiapoptotic proteins Bcl2 and Bcl-xL was also investigated following creatine treatment. Creatine increased Akt phosphorylation (Ser 473), and Bcl2 mRNA and protein levels, and Bcl-xL mRNA, whereas BAD mRNA was decreased following creatine administration in the hippocampus. Altogether these results indicate that creatine antidepressant-like effect may be dependent on Akt activation and increased expression of the neuroprotective proteins in the hippocampus of mice. The obtained data reinforce the antidepressant property of creatine and highlight the role of these molecular targets in the pathophysiology of MDD.

Thirty-five Day Fluoxetine Treatment Limits Sensory-Motor Deficit and Biochemical Disorders in a Rat Model of Decompression Sickness

According to the OECD statistical base for 2014, anti-depressants will, on average, be distributed at a rate of 62 daily doses per 1,000 inhabitants for the 25 countries surveyed (Health at a glance: Europe 2014; OECD Health Statistics; World Health Organization and OECD Health Statistics, 2014). Divers must be concerned. On another hand, divers are potentially exposed to decompression sickness including coagulation inflammation and ischemia, which can result in neurological lesions or even death. The purpose of this study is to assess whether chronic treatment with anti-depressants may represent a contraindication to the practice of an at-risk activity, such as, scuba diving, or even presents a benefit by attenuating the severity of the symptoms. We study for the first time the effect of a 35-day fluoxetine treatment (20 mg/kg) on the occurrence of decompression sickness in laboratory rats (n = 79). Following exposure to the hazardous protocol, there is a significant correlation between the type of treatment and the clinical status of the rats in favor of a better clinical prognosis for the rats treated with fluoxetine with a significantly higher number of No DCS status and a lower number of Severe DCS status in the Flux, compared to Controls. The treatment modifies the rat performances both significantly and favorably during the physical and behavioral tests, just like their biological and biochemical constants. After decompression, rats under treatment display lower sensory-motor deficit and lowers biochemical disorders. From a biological point of view, we conclude fluoxetine should not be seen as a contraindication for diving on the basis of anticipated increased physiological risk.

The alkaloids of Banisteriopsis caapi, the plant source of the Amazonian hallucinogen Ayahuasca, stimulate adult neurogenesis in vitro

Banisteriopsis caapi is the basic ingredient of ayahuasca, a psychotropic plant tea used in the Amazon for ritual and medicinal purposes, and by interested individuals worldwide. Animal studies and recent clinical research suggests that B. caapi preparations show antidepressant activity, a therapeutic effect that has been linked to hippocampal neurogenesis. Here we report that harmine, tetrahydroharmine and harmaline, the three main alkaloids present in B. caapi, and the harmine metabolite harmol, stimulate adult neurogenesis in vitro. In neurospheres prepared from progenitor cells obtained from the subventricular and the subgranular zones of adult mice brains, all compounds stimulated neural stem cell proliferation, migration, and differentiation into adult neurons. These findings suggest that modulation of brain plasticity could be a major contribution to the antidepressant effects of ayahuasca. They also expand the potential application of B. caapi alkaloids to other brain disorders that may benefit from stimulation of endogenous neural precursor niches.

Harmine stimulates proliferation of human neural progenitors

Harmine is the β-carboline alkaloid with the highest concentration in the psychotropic plant decoction Ayahuasca. In rodents, classical antidepressants reverse the symptoms of depression by stimulating neuronal proliferation. It has been shown that Ayahuasca presents antidepressant effects in patients with depressive disorder. In the present study, we investigated the effects of harmine in cell cultures containing human neural progenitor cells (hNPCs, 97% nestin-positive) derived from pluripotent stem cells. After 4 days of treatment, the pool of proliferating hNPCs increased by 71.5%. Harmine has been reported as a potent inhibitor of the dual specificity tyrosine-phosphorylation-regulated kinase (DYRK1A), which regulates cell proliferation and brain development. We tested the effect of analogs of harmine, an inhibitor of DYRK1A (INDY), and an irreversible selective inhibitor of monoamine oxidase (MAO) but not DYRK1A (pargyline). INDY but not pargyline induced proliferation of hNPCs similarly to harmine, suggesting that inhibition of DYRK1A is a possible mechanism to explain harmine effects upon the proliferation of hNPCs. Our findings show that harmine enhances proliferation of hNPCs and suggest that inhibition of DYRK1A may explain its effects upon proliferation in vitro and antidepressant effects in vivo.

Control of Cell Survival in Adult Mammalian Neurogenesis

The fact that continuous proliferation of stem cells and progenitors, as well as the production of new neurons, occurs in the adult mammalian central nervous system (CNS) raises several basic questions concerning the number of neurons required in a particular system. Can we observe continued growth of brain regions that sustain neurogenesis? Or does an elimination mechanism exist to maintain a constant number of cells? If so, are old neurons replaced, or are the new neurons competing for limited network access among each other? What signals support their survival and integration and what factors are responsible for their elimination? This review will address these and other questions regarding regulatory mechanisms that control cell-death and cell-survival mechanisms during neurogenesis in the intact adult mammalian brain.

Citalopram increases the differentiation efficacy of bone marrow mesenchymal stem cells into neuronal-like cells

Several studies have demonstrated that selective serotonin reuptake inhibitor antidepressants can promote neuronal cell proliferation and enhance neuroplasticity both in vitro and in vivo. It is hypothesized that citalopram, a selective serotonin reuptake inhibitor, can promote the neuronal differentiation of adult bone marrow mesenchymal stem cells. Citalopram strongly enhanced neuronal characteristics of the cells derived from bone marrow mesenchymal stem cells. The rate of cell death was decreased in citalopram-treated bone marrow mesenchymal stem cells than in control cells in neurobasal medium. In addition, the cumulative population doubling level of the citalopram-treated cells was significantly increased compared to that of control cells. Also BrdU incorporation was elevated in citalopram-treated cells. These findings suggest that citalopram can improve the neuronal-like cell differentiation of bone marrow mesenchymal stem cells by increasing cell proliferation and survival while maintaining their neuronal characteristics.

Lack of association of acute phase response proteins with hormone levels and antidepressant medication in perimenopausal depression

BACKGROUND

Major depression is associated with higher plasma levels of positive acute-phase proteins, as well as with lower plasma levels of negative acute-phase proteins. The aim of this study is to examine the levels of acute-phase response proteins and whether these levels are influenced by reproductive hormones and antidepressant medication in the perimenopausal depression.

METHODS

Sixty-five women (age range: 40-58 years old) participated in this study. All women were in the perimenopausal phase. The diagnosis of depression was made through a psychiatric interview and with the aid of Hamilton Depression Rating Scale 17 (HAM-D 17). The acute-phase response proteins, such as haptoglobin (HP), transferrine (TRf), α1-antitrypsin, complement protein 3 (C3), complement protein 4 (C4) and C-reactive protein (CRP) and the reproductive hormones, for example follicle-stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E2), were analyzed using standard laboratory methods. Pearson's correlations were applied to evaluate the relationship between acute-phase proteins and hormones.

RESULTS

Perimenopausal women were divided into three groups. The first group consisted of normal controls, the second one involved depressed perimenopausal women, who were taking selective serotonin reuptake inhibitors (SSRIs), and the third one included depressed women that were not treated with SSRIs. Depressed women in perimenopause, when being compared to non-depressed women, did not differ as to serum levels of acute-phase proteins. There was a positive correlation between HP and E2 in depressed perimenopausal women, who were not taking SSRIs.

CONCLUSIONS

The lack of association between acute-phase proteins and depressive mood mentioned in this study does not support previous findings in patients with major depression. This negative finding in perimenopausal depression indicates either the absence or a more complex nature of the interactions between acute-phase proteins, low-grade inflammation and depression. The hormonal profile of women is a part of this complexity, because it seems that in perimenopause the hormonal changes are accompanied by changes of acute-phase response proteins. Particularly, in perimenopausal depression, there is an interaction between HP and E2. Therefore, it seems that perimenopause is a period of a woman's life during which hormonal, immune and metabolic changes occur and interact with each other making women vulnerable to depression.

Effect of sertraline on proliferation and neurogenic differentiation of human adipose-derived stem cells

Background:

Antidepressant drugs are commonly employed for anxiety and mood disorders. Sertraline is extensively used as antidepressant in clinic. In addition, adipose tissue represents an abundant and accessible source of adult stem cells with the ability to differentiate in to multiple lineages. Therefore, human adipose-derived stem cells (hADSCs) may be useful for autologous transplantation.

Materials and Methods:

In the present study, we assessed the effect of antidepressant drug Sertraline on the proliferation and neurogenic differentiation of hADSCs using MTT assay and immunofluorescence technique respectively.

Results:

MTT assay analysis showed that 0.5 μM Sertraline significantly increased the proliferation rate of hADSCs induced cells (P < 0.05), while immunofluorescent staining indicated that Sertraline treatment during neurogenic differentiation could be decreased the percentage of glial fibrillary acidic protein and Nestin-positive cells, but did not significantly effect on the percentage of MAP2 positive cells.

Conclusion:

Overall, our data show that Sertraline can be promoting proliferation rate during neurogenic differentiation of hADSCs after 6 days post-induction, while Sertraline inhibits gliogenesis of induced hADSCs.

Sertraline increases the survival of retinoic acid induced neuronal cells but not glial cells from human mesenchymal stem cells

An increase in the number of viable in vitro differentiated neuronal cells is important for their use in clinics. A proportion of differentiated cells lose their viability before being used, and therefore we decided to use a pharmacological agent, sertraline, to increase neural cell differentiation and their survival. Purified endometrial stem cells (EnSCs) were examined for neuronal and glial cell specific markers after retinoic acid (RA) and sertraline treatment via RT-PCR, immunocytochemistry and Western blot analysis. The survival of differentiated cells was measured by MTT assay and the frequency of apoptosis, demonstrated by caspase-3-like activity. EnSCs were differentiated into neuronal cells after RA induction. Sertraline increased neuronal cell differentiation by 1.2-fold and their survival by 1.4-fold, and decreased from glial cell differentiation significantly. The findings indicate that sertraline could be used to improve the in vitro differentiation process of stem cells into neuronal cells, and may be involved in regenerative pharmacology in future.

Interleukin-1β inhibits the differentiation of hippocampal neural precursor cells into serotonergic neurons

Interleukin-1 beta (IL-1β) is one of pro-inflammatory cytokines. Recent studies have shown that IL-1β impairs hippocampal neurogenesis, mediates proliferation and differentiation of multipotent neural precursor cells (NPCs), and exerts effects of anti-proliferation, anti-neurogenesis, and pro-gliogenesis on embryonic hippocampal NPCs. The aim of this study was to examine the effect of IL-1β on the differentiation of hippocampal NPCs into functional serotonergic neurons, which play important roles in the pathophysiology and treatment of depression. Hippocampal NPCs were prepared from the hippocampus of neonatal rats (within 24h after birth). After three passages and phenotyping, hippocampal NPCs were cultured in a differentiating medium with various concentrations (5, 10, and 20 ng/mL) of IL-1β for 7 days. At the endpoint, the serotonergic differentiation of hippocampal NPCs in IL-1β-treated cultures decreased in a dose-dependent manner and this effect was blocked by IL-1ra, an IL-1 receptor antagonist capable of blocking the effects of IL-1 by binding to the same receptor (IL-1R1) without triggering signaling; serotonin in the lysate of the differentiated hippocampal NPCs decreased in IL-1β-treated cultures; and levels of Bcl-2 and phosphorylated extracellular-regulated kinase (pERK) were also lower in differentiated hippocampal NPCs with IL-1β treatment. These results support the hypothesis that IL-1β is an important factor in the stress-associated neuropathology and psychopathology and has relevance to the treatment of depressive symptoms in patients with depression.

Fluoxetine protects neurons against microglial activation-mediated neurotoxicity

Neuroinflammation is closely associated with the pathogenesis of Parkinson's disease (PD) and other neurological disorders. Increasing evidence suggests that inhibition of microglia-mediated neuroinflammation might represent a promising therapeutic potential for PD and related disorders. Fluoxetine, a selective serotonin reuptake inhibitor, is commonly used for the treatment of major depression due to its tolerability and safety profiles. Recent studies have shown that fluoxetine affords robust neuroprotection in a series of neurological disease models. However, the mechanism underlying fluoxetine-mediated neuroprotection remains unclear. Here, by using rat primary midbrain neuronglia cultures, we report that both R and S enantiomers of fluoxetine attenuated chronic neurodegeneration induced by a common inflammogen lipopolysaccharide (LPS) and a neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)). Reconstituted cell culture studies further revealed that microglia were required for fluoxetine-mediated neuroprotection. Fluoxetine significantly inhibited LPS-induced activation of microglia and subsequent release of multiple pro-inflammatory and cytotoxic factors including tumor necrosis factor-α, interleukin-1β, nitric oxide, and reactive oxygen species. Furthermore, inhibition of microglial NF-κB signaling pathway participated in fluoxetine-mediated neuroprotection. Collectively, fluoxetine exerted neuroprotection against microglia-mediated neurotoxicity. Thus, fluoxetine might hold a potential to retard inflammation-mediated chronic neurodegenerative process of PD.

Sertraline promotes hippocampus-derived neural stem cells differentiating into neurons but not glia and attenuates LPS-induced cellular damage

Sertraline is one of the most commonly used antidepressants in clinic. Although it is well accepted that sertraline exerts its action through inhibition of the reuptake of serotonin at presynaptic site in the brain, its effect on the neural stem cells (NSCs) has not been well elucidated. In this study, we utilized NSCs separated from the hippocampus of fetal rat to investigate the effect of sertraline on the proliferation and differentiation of NSCs. The study demonstrated that sertraline had no effect on NSCs proliferation but it significantly promoted NSCs to differentiate into serotoninergic neurons other than glia cells. Furthermore, we found that sertraline protected NSCs against the lipopolysaccharide-induced cellular damage. These data indicate that sertraline can promote neurogenesis and protect the viability of neural stem cells.

In animal models, psychosocial stress-induced (neuro)inflammation, apoptosis and reduced neurogenesis are associated to the onset of depression

Recently, the inflammatory and neurodegenerative (I&ND) hypothesis of depression was formulated (Maes et al., 2009), i.e. the neurodegeneration and reduced neurogenesis that characterize depression are caused by inflammation, cell-mediated immune activation and their long-term sequels. The aim of this paper is to review the body of evidence that external stressors may induce (neuro)inflammation, neurodegeneration and reduced neurogenesis; and that antidepressive treatments may impact on these pathways. The chronic mild stress (CMS) and learned helplessness (LH) models show that depression-like behaviors are accompanied by peripheral and central inflammation, neuronal cell damage, decreased neurogenesis and apoptosis in the hippocampus. External stress-induced depression-like behaviors are associated with a) increased interleukin-(IL)1β, tumor necrosis factor-α, IL-6, nuclear factor κB, cyclooxygenase-2, expression of Toll-like receptors and lipid peroxidation; b) antineurogenic effects and reduced brain-derived neurotrophic factor (BDNF) levels; and c) apoptosis with reduced levels of Bcl-2 and BAG1 (Bcl-2 associated athanogene 1), and increased levels of caspase-3. Stress-induced inflammation, e.g. increased IL-1β, but not reduced neurogenesis, is sufficient to cause depression. Antidepressants a) reduce peripheral and central inflammatory pathways by decreasing IL-1β, TNFα and IL-6 levels; b) stimulate neuronal differentiation, synaptic plasticity, axonal growth and regeneration through stimulatory effects on the expression of different neurotrophic factors, e.g. trkB, the receptor for brain-derived neurotrophic factor; and c) attenuate apoptotic pathways by activating Bcl-2 and Bcl-xl proteins, and suppressing caspase-3. It is concluded that external stressors may provoke depression-like behaviors through activation of inflammatory, oxidative, apoptotic and antineurogenic mechanisms. The clinical efficacity of antidepressants may be ascribed to their ability to reverse these different pathways.

Ageing and neurodegenerative diseases

Ageing, which all creatures must encounter, is a challenge to every living organism. In the human body, it is estimated that cell division and metabolism occurs exuberantly until about 25 years of age. Beyond this age, subsidiary products of metabolism and cell damage accumulate, and the phenotypes of ageing appear, causing disease formation. Among these age-related diseases, neurodegenerative diseases have drawn a lot of attention due to their irreversibility, lack of effective treatment, and accompanied social and economical burdens. In seeking to ameliorate ageing and age-related diseases, the search for anti-ageing drugs has been of much interest. Numerous studies have shown that the plant polyphenol, resveratrol (3,5,4'-trihydroxystilbene), extends the lifespan of several species, prevents age-related diseases, and possesses anti-inflammatory, and anti-cancer properties. The beneficial effects of resveratrol are believed to be associated with the activation of a longevity gene, SirT1. In this review, we discuss the pathogenesis of age-related neurodegenerative diseases including Alzheimer's disease, Parkinson's disease and cerebrovascular disease. The therapeutic potential of resveratrol, diet and the roles of stem cell therapy are discussed to provide a better understanding of the ageing mystery.

Fluoxetine promotes gliogenesis during neural differentiation in mouse embryonic stem cells

Selective serotonin reuptake inhibitors (SSRIs) are commonly prescribed for treatment of mood disorders and depression, even during pregnancy and lactation. SSRIs are thought to be much safer than tricyclic antidepressants, with a low risk of embryonic toxicity. Several recent studies, however, have reported that fetal exposure to SSRIs increases the risk of adverse effects during fetal and neonatal development. This is consistent with our previous finding that fluoxetine, a prototypical SSRI, profoundly affected the viability of cultured embryonic stem (ES) cells as well as their ability to differentiate into cardiomyocytes. Furthermore, we found that fluoxetine induced fluctuations in ectodermal marker gene expression during ES cell differentiation, which suggests that fluoxetine may affect neural development. In the present study, we investigated the effects of fluoxetine on the process of differentiation from ES cells into neural cells using the stromal cell-derived inducing activity (SDIA) method. Fluoxetine treatment was found to enhance the expression of glial marker genes following neural differentiation, as observed by immunocytochemical analysis or quantitative RT-PCR. The promoter activity of glial marker genes was also significantly enhanced when cells were treated with fluoxetine, as observed by luciferase reporter assay. The expression of neuronal markers during ES cell differentiation into neural cells, on the other hand, was inhibited by fluoxetine treatment. In addition, FACS analysis revealed an increased population of glial cells in the differentiating ES cells treated with fluoxetine. These results suggest that fluoxetine could facilitate the differentiation of mouse ES cells into glial cell lineage, which may affect fetal neural development.

Stem cell-based neuroprotective and neurorestorative strategies

Stem cells, a special subset of cells derived from embryo or adult tissues, are known to present the characteristics of self-renewal, multiple lineages of differentiation, high plastic capability, and long-term maintenance. Recent reports have further suggested that neural stem cells (NSCs) derived from the adult hippocampal and subventricular regions possess the utilizing potential to develop the transplantation strategies and to screen the candidate agents for neurogenesis, neuroprotection, and neuroplasticity in neurodegenerative diseases. In this article, we review the roles of NSCs and other stem cells in neuroprotective and neurorestorative therapies for neurological and psychiatric diseases. We show the evidences that NSCs play the key roles involved in the pathogenesis of several neurodegenerative disorders, including depression, stroke and Parkinson’s disease. Moreover, the potential and possible utilities of induced pluripotent stem cells (iPS), reprogramming from adult fibroblasts with ectopic expression of four embryonic genes, are also reviewed and further discussed. An understanding of the biophysiology of stem cells could help us elucidate the pathogenicity and develop new treatments for neurodegenerative disorders. In contrast to cell transplantation therapies, the application of stem cells can further provide a platform for drug discovery and small molecular testing, including Chinese herbal medicines. In addition, the high-throughput stem cell-based systems can be used to elucidate the mechanisms of neuroprotective candidates in translation medical research for neurodegenerative diseases.

Fluoxetine induces apoptosis in ovarian carcinoma cell line OVCAR-3 through reactive oxygen species-dependent activation of nuclear factor-kappaB

The apoptotic effect of fluoxetine (FLX), an antidepressant, against human epithelial ovarian cancer cell lines OVCAR-3 and SK-OV-3 was investigated in relation to the mitochondria-mediated cell death process and nuclear factor (NF)-kappaB activation. FLX-induced mitochondrial membrane permeability change and formation of reactive oxygen species, leading to cell death. FLX-induced increase in mitochondrial Bax levels, decrease in cytosolic Bid and Bcl-2 levels, loss of the mitochondrial transmembrane potential, cytochrome c release, caspase-3 activation and up-regulation of p53. Oxidant scavengers and Bay 11-7085 [an inhibitor of nuclear factor kappaB (NF-kappaB) activation] prevented the FLX-induced cell death, increase in phosphorylated inhibitory kappaB-alpha and NF-kappaB p65 levels, and binding of NF-kappaB p65 to DNA. Results from this study suggest that FLX may exhibit apoptotic effect against ovarian cancer cell lines by inducing the mitochondrial membrane permeability change, which leads to cytochrome c release and subsequent caspase-3 activation, through reactive oxygen species-dependent activation of NF-kappaB.

Ageing abolishes the effects of fluoxetine on neurogenesis

Depression constitutes a widespread condition observed in elderly patients. Recently, it was found that several drugs employed in therapies against depression stimulate hippocampal neurogenesis in young rodents and nonhuman primates. As the rate of neurogenesis is dramatically reduced during ageing, we examined the influences of ageing on neurogenic actions of antidepressants. We tested the impact of fluoxetine, a broadly used antidepressant, on hippocampal neurogenesis in mice of three different age groups (100, 200 and over 400 days of age). Proliferation and survival rate of newly generated cells, as well as the percentage of cells that acquired a neuronal phenotype were analyzed in the hippocampus of mice that received fluoxetine daily in a chronic manner. Surprisingly, the action of fluoxetine on neurogenesis was decreasing as a function of age and was only significant in young animals. Hence, fluoxetine increased survival and the frequency of neuronal marker expression in newly generated cells of the hippocampus in the young adult group (that is 100 days of age) only. No significant effects on neurogenesis could be detected in fluoxetine-treated adult and elderly mice (200 and over 400 days of age). The data indicate that the action of fluoxetine on neurogenesis is highly dependent on the age of the treated individual. Although the function of neurogenesis in the clinical manifestation of depression is currently a matter of speculation, this study clearly shows that the therapeutic effects of antidepressants in elderly patients are not mediated by neurogenesis modulation.

Effects of typical (haloperidol) and atypical (risperidone) antipsychotic agents on protein expression in rat neural stem cells

Neural stem cells (NSCs) play a crucial role in the development and maturation of the central nervous system. Recently studies suggest that antipsychotic drugs regulate the activities of NSCs. However, the molecular mechanisms underlying antipsychotic-induced changes of the activity of NSCs, particularly protein expression, are still unknown. We studied the growth and protein expression in haloperidol (HD) and risperidone (RS) treated rat NSCs. The treatment with RS (3microM) or HD (3microM) had no effect on morphology of NSCs after 24h, but significantly promotes or inhibits the differentiation of NSCs after a 96h of treatment. 2-DE based proteomics was performed at 24h, a stage before phenotypic expression of NSCs. Gel image analysis revealed that 30 protein spots in HD- and 60 spots in RS-treated groups were differentially regulated in their expression compared to control group (p<0.05; ANOVA). When these spots were compared between the two drug-treated groups, 23 spots overlapped leaving 7 HD-specific and 37 RS-specific spots. Of these 67 spots, 32 different proteins were identified. The majority of the differentially regulated proteins were classified into several functional groups, such as cytoskeletal, calcium regulating protein, metabolism, signal transduction and proteins related to oxidative stress. Our data shows that atypical RS expressed more proteins than typical HD, and these results might explain the molecular mechanisms underlying the different effects of both drugs on NSCs activities as described above. Identified proteins in this experiment may be useful in future studies of NSCs differentiation and/or understanding in molecular mechanisms of different neural diseases including schizophenia.

Antiapoptotic and neurotrophic effects of antidepressants: a review of clinical and experimental studies

Recent studies have strengthened the role of the abnormalities in neurotrophic pathways in the pathophysiology of depression. It has been shown that the depletion of growth factors, particularly brain-derived neurotrophic factor, may result in depression-like behavior in animals and may induce cellular changes that are reminiscent of those observed in depressed patients. Some authors even suggested that increased neuronal cell loss may contribute to the pathogenesis of depression. Hence, appreciable interest has been focused on the trophic and antiapoptotic effects of antidepressant drugs. In this paper, we put emphasis on the contribution of hippocampal atrophy, increased cell death and alterations in trophic factors to the pathogenesis of depression and their relationship to the potential of antidepressants to reverse these changes by modulating trophic factor cascades and preventing apoptosis. First, evidences for increased hippocampal atrophy and cell death in depression are discussed, followed by a review of selected studies of special interest that concern antiapoptotic action of antidepressant drugs. Next, depression-related neurotrophic abnormalities and their reversal by antidepressants are depicted. Finally, relationships among neurotrophins, antiapoptotic proteins and antioxidant enzymes in the pathology and treatment of depression are pointed out.

Brain-derived neurotrophic factor, stress and depression: a minireview

Brain-derived neurotrophic factor (BDNF) is a member of the nerve growth factor family, and is widely expressed in the adult mammalian brain. Besides its well known neuroprotective activity after traumatic brain injury the evidences regarding its activity dependent release by the pathophysiology of major depression are rapidly replicating. Considering the data that stress plays an important role by the development of depression which is characterized with prominent hippocampal cell death, as well as the well known neuroprotective effects of BDNF, we aimed to investigate the link between the BDNF, stress and depression. Thus we prepared a minireview in order to evaluate the neuroprotective role of BDNF by psychiatric disorders which are characterized with prominent neuronal cell death.

Fluoxetine-induced proliferation and differentiation of neural progenitor cells isolated from rat postnatal cerebellum

Previous studies have shown that the serotonin-reuptake inhibitor (SSRI) fluoxetine affects neural progenitors derived from postnatal cerebellum or adult hippocampus and stimulates their proliferation. In the human cerebellum, the proliferation of cerebellar granule cells (CGC) continues until the 11th postnatal month and could be influenced in infants by breastfeeding-delivered SSRIs. Current information about fluoxetine effects on postnatal cerebellar neural progenitors is limited. Here we report the characterization of fluoxetine actions on rat postnatal cerebellar neural progenitors. RT-PCR and immunostaining revealed the expression of serotonin transporter (SERT), 5HT(1A) receptors, tryptophan hydroxylase (TPH), and serotonin (5HT). Protracted in vitro fluoxetine treatment increased cell proliferation and differentiation. The proliferative effects of fluoxetine, 5HT, and the selective agonist of 5HT(1A) receptors trans-8-hydroxy-2-(N-n-propyl-N-3'-iodo-2'-propenyl)aminotetralin (8-OH-PIPAT) were abolished by the selective antagonist of 5HT(1A) receptors, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide trihydrochloride (WAY-100635). Furthermore, fluoxetine-induced activation of both the cAMP-response element-binding (CREB) protein and extracellular signal-regulated protein kinases (ERK1/2), which was abolished by the selective inhibitor of MAP kinase kinase (MEK) 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene (U0126), and increased cyclin D1 expression. All these effects were prevented by WAY-100635. Collectively, our results demonstrate that rat postnatal cerebellum contains neural progenitors capable of proliferating and differentiating in response to fluoxetine exposure, possibly through the activation of 5HT(1A) receptors. The relevance of these findings for possible SSRI effects on the developing postnatal/infant human cerebellum should be explored.

Evidence for an inhibitory immunomodulatory effect of selected antidepressants on rat splenocytes: possible relevance to depression and hyperactive-immune disorders

Antidepressants have been found to possess antiproliferative effect. In the immune system depression may activate pro-inflammatory cytokines. Therefore, the aim of this study was to assess the immunomodulatory activity of antidepressants in naïve rat. Rat splenocytes were activated with con A and treated with paroxetine, sertraline or clomipramine ex vivo. We found that the antidepressants inhibit cell viability and proliferation at IC50 of 5-8 microM of mitogen-stimulated rat splenocytes. This inhibitory effect was accompanied by cell cycle arrest and increase in apoptotic events as assayed by FACS. Moreover, antidepressants decrease the secretion of the TH1 factor--TNFalpha. In addition, the antidepressants reduced the expression of the enzyme cyclooxygenase2 which is involved in inflammation. On the cellular level we show the up-regulation of MAPK death signaling pathway and suppression of the anti-apoptotic factor--Bcl-2. These findings reveal the immunomodulatory effect of the selected antidepressants. These data suggest a novel use of antidepressants or their derivatives.

Eat less, live longer? New insights into the role of caloric restriction in the brain

Caloric restriction has wide-ranging health benefits and may offer protection against age-related neuronal loss and neurodegenerative disorders such as Alzheimer's disease, possibly via enhanced adult neurogenesis. While a variety of interventions such as exercise increase neurogenesis, recent work suggests that exercise and caloric restriction may work to enhance neurogenesis by different neurobiological mechanisms, suggesting a role for both diet and exercise in disease prevention.