miR-16 and Fluoxetine Both Reverse Autophagic and Apoptotic Change in Chronic Unpredictable Mild Stress Model Rats

Brain-derived neurotrophic factor in 5-HT neurons regulates susceptibility to depression-related behaviors induced by subchronic unpredictable stress

Chronic stress is a major risk factor for the development of depression. Brain-derived neurotrophic factor (BDNF) plays an important role in neural functions and exhibits antidepressant effects. However, studies on depression-related behavioral response to BDNF have mainly focused on the limbic system, whereas other regions of the brain still require further exploration. Here, we report that exposure to chronic unpredictable stress (CUS) can induce depression-associated behaviors in mice. CUS could decrease total Bdnf mRNA and protein levels in the dorsal raphe nucleus (DRN), which correlated with depression-related behaviors. A corresponding reduction in exon-specific Bdnf mRNA was observed in the DRN of CUS mice. Bdnf was highly expressed in 5- Hydroxytryptamine (5-HT) neurons from the DRN. Selective deletion of Bdnf in 5-HT neurons alone could not induce anhedonia and behavioral despair in male or female mice, as indicated by the unchanged female urine sniffing time and preference for sucrose/saccharin. However, it could increase the latency to food in female mice, but not in male mice as shown by novelty-suppressed food test. Nevertheless, enhanced stress-induced susceptibility is observed in these male mice as suggested by the decrease in female urine sniffing time, and for female mice by the reduced sucrose preference and increased immobility in forced swim test. Furtherly, total Bdnf mRNA levels in DRN were correlated with depression-related behaviors of female, but not male 5-HT neurons specific Bdnf knockout mice. Our results indicate that BDNF might act on 5-HT neurons to regulate depression-related behaviors and stress vulnerability in a sex-dependent manner.

Optimization of food deprivation and sucrose preference test in SD rat model undergoing chronic unpredictable mild stress

BACKGROUND

The chronic unpredictable mild stress (CUMS) model has long been considered the best model for exploring the pathophysiological mechanisms underlying depression. However, there are no widely recognised standards for strategies for modeling and for behavioral testing. The present study aimed to optimize the protocols for food deprivation and the sucrose preference test (SPT) for the CUMS model.

METHODS

We first evaluated the effects of different long periods of food deprivation on the body weight of Sprague Dawley (SD) rats by testing food deprivation for 24 hours (8:00-8:00+), food deprivation for 12 hours during the daytime (8:00-20:00) and food deprivation for 12 hours at night (20:00-8:00+). Next, we established a SD rat CUMS model with 15 different stimulations, and used body weight measurement, SPT, forced swim test (FST), open field test (OFT) and Morris water maze (MWM) test to verify the success of the modeling. In the SPT, consumption of sucrose and pure water within 1 and 12 hours was measured.

RESULTS

Twelve hours of food deprivation during the daytime (8:00-20:00) had no effect on body weight, while 12 hours of food deprivation at night (20:00-8:00+) and 24 hours of food deprivation (8:00-8:00+) significantly reduced the mean body weight of the SD rats. When SPT was used to verify the successful establishment of the CUMS rat model, sucrose consumption measured within 12 hours was less variable than that measured within 1 hour.

CONCLUSIONS

Twelve hours of food deprivation in the daytime (8:00-20:00) may be considered a mild stimulus for the establishment of a CUMS rat model. Measuring sucrose consumption over 12 hours is recommended for SPT.

Effect of Electroacupuncture on Reuptake of Serotonin via miRNA-16 Expression in a Rat Model of Depression

The current study aimed to investigate the effects and mechanisms of electroacupuncture (EA) treatment applied to Bai hui (GV20) and Yin tang (GV29) acupoints (1 mA, 2 Hz, continuous wave, 20 minutes) for 28 days in a rat model of chronic unpredictable mild stress (CUMS) on reuptake of serotonin (5-hydroxytryptamine (5-HT)) and miRNA-16 levels in the hippocampus and serum. Rats were housed in individual cages, and CUMS was used to establish a rat model of depression. After EA treatment for 4 weeks, behavioral changes and indices including 5-HT transporter (SERT), 5-HT, and miRNA-16 levels in the hippocampus and serum were examined. The EA treatment significantly improved base levels of sucrose preference and exploratory behavior and significantly decreased SERT protein and mRNA expression in the hippocampus of depressed rats. Significantly increased 5-HT levels were observed, and miRNA-16 levels were significantly decreased in the hippocampus and serum of depressed rats. In conclusion, the antidepressant effects of EA treatment may be affected via inhibition of 5-HT reuptake, upregulation of 5-HT levels, and inhibition of miRNA-16 expression in the hippocampus and serum.

Differential Impact of Co-expressed SP-A1/SP-A2 Protein on AM miRNome; Sex Differences

In humans there are two surfactant protein A (SP-A) functional genes SFTPA1 and SFTPA2 encoding innate immune molecules, SP-A1 and SP-A2, respectively, with numerous genetic variants each. SP-A interacts and regulates many of the functions of alveolar macrophages (AM). It is shown that SP-A variants differ in their ability to regulate the AM miRNome in response to oxidative stress (OxS). Because humans have both SP-A gene products, we were interested to determine the combined effect of co-expressed SP-A1/SP-A2 (co-ex) in response to ozone (O₃) induced OxS on AM miRNome. Human transgenic (hTG) mice, carrying both SP-A1/SP-A2 (6A²/1A⁰, co-ex) and SP-A- KO were utilized. The hTG and KO mice were exposed to filtered air (FA) or O₃ and miRNA levels were measured after AM isolation with or without normalization to KO. We found: (i) The AM miRNome of co-ex males and females in response to OxS to be largely downregulated after normalization to KO, but after Bonferroni multiple comparison analysis only in females the AM miRNome remained significantly different compared to control (FA); (ii) The targets of the significantly changed miRNAs were downregulated in females and upregulated in males; (iii) Several of the validated mRNA targets were involved in pro-inflammatory response, anti-apoptosis, cell cycle, cellular growth and proliferation; (iv) The AM of SP-A2 male, shown, previously to have major effect on the male AM miRNome in response to OxS, shared similarities with the co-ex, namely in pathways involved in the pro-inflammatory response and anti-apoptosis but also exhibited differences with the cell-cycle, growth, and proliferation pathway being involved in co-ex and ROS homeostasis in SP-A2 male. We speculate that the presence of both gene products vs. single gene products differentially impact the AM responses in males and females in response to OxS.

Xiaoyaosan exerts antidepressant-like effects by regulating the functions of astrocytes and EAATs in the prefrontal cortex of mice

BACKGROUND

Mounting evidence indicates that the cerebral cortex is an important physiological system of emotional activity, and its dysfunction may be the main cause of stress. Glutamate is the primary excitatory neurotransmitter in the central nervous system (CNS), which initiates rapid signal transmission in the synapse before its reuptake into the surrounding glia, specifically astrocytes (ASTs). The astrocytic excitatory amino acid transporters 1 (EAAT1) and 2 (EAAT2) are the major transporters that take up synaptic glutamate to maintain optimal extracellular glutamic levels, thus preventing accumulation in the synaptic cleft and ensuing excitotoxicity. Growing evidence has shown that excitotoxicity is associated with depression. Therefore, we hypothesized that the underlying antidepressant-like mechanism of Xiaoyaosan (XYS), a Chinese herbal formula, may be related to the regulation of astrocytic EAATs. Therefore, we studied the antidepressant mechanism of XYS on the basis of EAAT dysfunction in ASTs.

METHODS

Eighty adult C57BL/6 J mice were randomly divided into 4 groups: a control group, a chronic unpredictable mild stress (CUMS) group, a Xiaoyaosan (XYS) treatment group and a fluoxetine hydrochloride (Flu) treatment group. Except for the control group, mice in the other groups all received chronic unpredictable mild stress for 21 days. Mice in the control and CUMS groups received gavage administration with 0.5 mL of normal saline (NS) for 21 days, and mice in the XYS and Flu treatment groups were administered dosages of 0.25 g/kg/d and 2.6 mg/kg/d by gavage. The effects of XYS on the depressive-like behavioral tests, including the open field test (OFT), forced swimming test (FST) and sucrose preference test (SPT), were examined. The glutamate (Glu) concentrations of the prefrontal cortex (PFC) were detected with colorimetry. The morphology of neurons in the PFC was observed by Nissl staining. The expression of glial fibrillary acidic protein (GFAP), NeuN, EAAT1 and EAAT2 proteins in the PFC of mice was detected by using Western blotting and immunohistochemistry. Quantitative real-time PCR (qPCR) was used to detect the expression of the GFAP, NeuN, EAAT1 and EAAT2 genes in the PFC of mice.

RESULTS

The results of behavioral tests showed that CUMS-induced mice exhibited depressive-like behavior, which could be improved in some tests with XYS and Flu treatment. Immunohistochemistry and Western blot analysis showed that the protein levels of GFAP, NeuN, EAAT1 and EAAT2 in the PFC of CUMS mice were significantly lower than those in the control group, and these changes could be reversed by XYS and Flu. The results of qPCR analysis showed that the expression of GFAP, NeuN, EAAT1 and EAAT2 mRNAs in the PFC of CUMS mice was not significantly changed, with the exception of EAAT2, compared with that of the control group, while the expression of the above mRNAs was significantly higher in the XYS and Flu groups than that in the CUMS group.

CONCLUSION

XYS may exert antidepressant-like effects by improving the functions of AST and EAATs and attenuating glutamate-induced neuronal damage in the frontal cortex.

The Missing Link: How Exosomes and miRNAs can Help in Bridging Psychiatry and Molecular Biology in the Context of Depression, Bipolar Disorder and Schizophrenia

MicroRNAs (miRNAs) only recently have been recognized as promising molecules for both fundamental and clinical neuroscience. We provide a literature review of miRNA biomarker studies in three most prominent psychiatric disorders (depression, bipolar disorder and schizophrenia) with the particular focus on depression due to its social and healthcare importance. Our search resulted in 191 unique miRNAs across 35 human studies measuring miRNA levels in blood, serum or plasma. 30 miRNAs replicated in more than one study. Most miRNAs targeted neuroplasticity and neurodevelopment pathways. Various limitations do not allow us to make firm conclusions on clinical potential of studied miRNAs. Based on our results we discuss the rationale for future research investigations of exosomal mechanisms to overcome methodological caveats both in studying etiology and pathogenesis, and providing an objective back-up for clinical decisions.

Chronic unpredictable mild stress-induced behavioral changes are coupled with dopaminergic hyperfunction and serotonergic hypofunction in mouse models of depression

Accumulating evidence shows that stressful events evoke molecular alterations in the brain, considered a pathology in major depressive disorder (MDD). However, the abnormalities of neurotransmissions as well as intracellular signaling pathways affected by chronic stress in brain have not been fully explored. We investigated the effect of chronic unpredictable mild stress (CUMS) on the emotional behaviors, dopaminergic and serotoninergic function, and intracellular signaling in the nucleus accumbens, hippocampus and prefrontal cortex. Male C57BL/6J mice were exposed to CUMS for 4 weeks. CUMS was shown to induce hyperactivity in a novel environment, decrease interaction time in the social interaction test, prolong feeding latency in the novelty suppressed feeding test and enhance immobility in the forced swimming test. The levels of dopamine, its metabolites and turnover, and protein level of tyrosine hydroxylase (TH) were increased by CUMS in the nucleus accumbens (NAc). The level of serotonin and protein levels of tryptophan hydroxylase (TPH) and TH were decreased by CUMS in the hippocampus (HPC) and prefrontal cortex (PFC). Accompanying the increase in dopaminergic function, phosphorylation levels of extracellular signal-regulated kinases (ERK), protein kinase B (Akt) and cAMP response element-binding protein (CREB) were increased by CUMS in the NAc. Administration of fluoxetine (selective serotonin re-uptake inhibitor: 20 mg/kg i.p.) and aripiprazole (dopamine D₂ receptor partial agonist: 0.1 mg/kg i.p.) during CUMS, prevented behavioral changes and increase of dopamine level in the NAc. These data suggest that CUMS-induced depression-like behaviors are coupled with dopaminergic hyperfunction in the NAc and serotonergic hypofunction in the HPC and PFC.

Immune mechanisms of stress susceptibility and resilience: Lessons from animal models

Stress has an impact on the brain and the body. A growing literature demonstrates that feedback between the peripheral immune system and the brain contributes to individual differences in the behavioral response to stress. Here we examine preclinical literature to demonstrate a holistic vision of risk and resilience to stress. We identify a variety of cellular, cytokine and molecular mechanisms in adult animals that act in concert to produce a stress susceptible individual response. We discuss how cross talk between immune cells in the brain and in the periphery act together to increase permeability across the blood brain barrier or block it, resulting in susceptible or stress resilient phenotype. These preclinical studies have importance for understanding how individual differences in the immune response to stress may be contributing to mood related disorders such as depression, anxiety and posttraumatic stress disorders.

Progesterone and fluoxetine treatments of postpartum depressive-like behavior in rat model

Research studies have indicated that alterations in plasma progesterone levels might be associated with the hippocampal synaptic plasticity of postpartum depressive-like behavior. Herein, we assess both progesterone and fluoxetine effects in adult female Sprague-Dawley rats with postpartum depressive-like behavior. Depressive-like behavior of postpartum rats was established using chronic ultra-mild stress (CUMS) method for 1 week from gestation day 15. Postpartum rats that showed depressive-like behavior were treated with either progesterone (subcutaneously, 0.5 mg/kg) from gestation day 17 to gestation day 22 or fluoxetine (by gavage, 10 mg/kg/day) for 4 weeks after birth. Open field and sucrose preference tests were conducted at the start, week 2 and week 4 postpartum. Golgi staining, immunofluorescence and Western blot analyses of rats' hippocampi were conducted on week 4 postpartum. Results showed CUMS increases depressive-like behavior, however, treatment with progesterone and fluoxetine improves this behavior. Both progesterone and fluoxetine treatments increase the numbers of dendritic spines pyramidal neurons in the CA3 region of the hippocampus as well as protein expression levels of microtubule-associated protein 2 (MAP-2) and synaptophysin (SYP). CUMS-induced decrement of MAP-2 and SYP protein expressions can be prevented by treatment with progesterone in advanced pregnant stage and fluoxetine in the postpartum period.

HCN channels: New targets for the design of an antidepressant with rapid effects

BACKGROUND

Major depressive disorder (MDD) is a prevalent neuropsychiatric disease that carries a staggering global burden. Although numerous antidepressants are available on the market, unfortunately, many patients die by committing suicide as a result of the therapeutic lag between treatment initiation and the improvement of depressive symptoms. This therapeutic lag highlights the need for new antidepressants that provide rapid relief of depressive symptoms.

METHOD

In this review, we discuss the seminal researches on hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in animal models of depression and highlight the substantial evidence supporting the development of rapid-acting antidepressants targeting HCN channels.

RESULTS

HCN channels are associated with the risk of depression and targeting HCN channels or its auxiliary subunit tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) function may exert a rapid antidepressant-like effect.

CONCLUSIONS

Compounds acting on HCN subunits or the TRIP8b-HCN interaction site may be excellent candidates for development into effective drugs with rapid antidepressant action.

Multifaceted Regulations of the Serotonin Transporter: Impact on Antidepressant Response

Serotonin transporter, SERT (SLC64A for solute carrier family 6, member A4), is a twelve transmembrane domain (TMDs) protein that assumes the uptake of serotonin (5-HT) through dissipation of the Na⁺ gradient established by the electrogenic pump Na/K ATPase. Abnormalities in 5-HT level and signaling have been associated with various disorders of the central nervous system (CNS) such as depression, obsessive-compulsive disorder, anxiety disorders, and autism spectrum disorder. Since the 50s, SERT has raised a lot of interest as being the target of a class of antidepressants, the Serotonin Selective Reuptake Inhibitors (SSRIs), used in clinics to combat depressive states. Because of the refractoriness of two-third of patients to SSRI treatment, a better understanding of the mechanisms regulating SERT functions is of priority. Here, we review how genetic and epigenetic regulations, post-translational modifications of SERT, and specific interactions between SERT and a set of diverse partners influence SERT expression, trafficking to and away from the plasma membrane and activity, in connection with the neuronal adaptive cell response to SSRI antidepressants.

GRP Receptor Regulates Depression Behavior via Interaction With 5-HT2a Receptor

OBJECTIVE

Accumulating evidences indicate that gastrin-releasing peptide receptor (GRPR) may contribute to the pathophysiology of depression. However, the mechanism of the involvement of GRPR in the progression of depression remains unclear. Here, we showed the extent to which stress and antidepressant treatment impact GRPR expression, and explored the interactions between 5-HT2a receptor (5-HT2aR) and GRPR at the cellular level.

METHODS

The rat depression models were created with chronic unpredictable mild stress (CUMS). Then, these rats were treated with fluoxetine for 4 weeks after CUMS. We measured body weight and performed behavioral tests to determine the effects of stress and fluoxetine on depressive-like behaviors. Real-time PCR and western blotting were used to measure the mRNA and protein expression levels of GRPR in the hypothalamus. Then, Flag-tagged protein (pcmv-Flag-5HT2aR) and Myc-tagged protein (pcmv-Myc-GRPR) expression vectors were constructed, identified, and transfected into human embryo kidney 293 (HEK293) cells. The interaction between 5-HT2aR and GRPR was detected by coimmunoprecipitation and double-label immunofluorescence.

RESULTS

The rats subjected to 4 weeks of CUMS showed depressive-like behaviors, including decreased body weight, sucrose preference, and distance traveled, rearing frequency and velocity in the open field test and increased immobility time in the forced swimming test. Fluoxetine treatment reversed CUMS-induced depressive-like behavior. The mRNA and protein expression of GRPR in the hypothalamus was significantly increased after 4 weeks CUMS exposure, and treatment with fluoxetine reversed these changes. Coimmunoprecipitation showed that 5-HT2aR and GRPR combine with each other in vitro. Immunofluorescence revealed that the 5-HT2aR and GRPR were colocalization in both the cell membrane and cytoplasm.

CONCLUSION

Our study enhances the understanding of the involvement of GRPR in depression. This study also provides in vitro experimental evidence of the interaction between 5-HT2aR and GRPR, which may play an important role in the pathogenesis of depression.

Advance in Stress for Depressive Disorder

Stress is an adaptive response to environment aversive stimuli and a common life experience of one's daily life. Chronic or excessive stress especially that happened in early life is found to be deleterious to individual's physical and mental health, which is highly related to depressive disorders onset. Stressful life events are consistently considered to be the high-risk factors of environment for predisposing depressive disorders. In linking stressful life events with depressive disorder onset, dysregulated HPA axis activity is supposed to play an important role in mediating aversive impacts of life stress on brain structure and function. Increasing evidence have indicated the strong association of stress, especially the chronic stress and early life stress, with depressive disorders development, while the association of stress with depression is moderated by genetic risk factors, including polymorphism of SERT, BDNF, GR, FKBP5, MR, and CRHR1. Meanwhile, stressful life experience particularly early life stress will exert epigenetic modification in these risk genes via DNA methylation and miRNA regulation to generate long-lasting effects on these genes expression, which in turn cause brain structural and functional alteration, and finally increase the vulnerability to depressive disorders. Therefore, the interaction of environment with gene, in which stressful life exposure interplay with genetic risk factors and epigenetic modification, is essential in predicting depressive disorders development. As the mediator of environmental risk factors, stress will function together with genetic and epigenetic mechanism to influence brain structure and function, physiology and psychology, and finally the vulnerability to depressive disorders.

Is There a Role of Autophagy in Depression and Antidepressant Action?

Autophagy has been recognized as evolutionary conserved intracellular pathway that ensures energy, organelle, and protein homeostasis through lysosomal degradation of damaged macromolecules and organelles. It is activated under various stress situations, e.g., food deprivation or proteotoxic conditions. Autophagy has been linked to several diseases, more recently also including stress-related diseases such as depression. A growing number of publications report on the role of autophagy in neurons, also referred to as "neuronal autophagy" on the one hand, and several studies describe effects of antidepressants-or of compounds that exert antidepressant-like actions-on autophagy on the other hand. This minireview highlights the emerging evidence for the involvement of autophagy in the pathology and treatment of depression and discusses current limitations as well as potential avenues for future research.

Antidepressant-Like Effects of Low- and High-Molecular Weight FGF-2 on Chronic Unpredictable Mild Stress Mice

The occurrence of depressive disorder has long been attributed to changes in monoamines, with the focus of drug treatment strategies being to change the effectiveness of monoamines. However, the success achieved by changing these processes is limited and further stimulates the exploration of alternative mechanisms and treatments. Fibroblast growth factor 2 (FGF-2), which occurs in a high-molecular weight (HMW) and low-molecular weight (LMW) form, is a potent developmental modulator and nervous system regulator that has been suggested to play an important role in various psychiatric disorders. In this study, we investigated the antidepressant effects of HMW and LMW FGF-2 on depression induced by chronic stress. Both peripheral LMW and HMW FGF-2 attenuated the depression-like behaviors in chronic unpredictable mild stress (CUMS) mice to a similar extent, as determined by the forced swimming, tail suspension, and sucrose preference tests. We then showed that CUMS-induced oxidative stresses in mice were inhibited by FGF-2 treatments both in central and peripheral. We also showed that both forms of FGF-2 increased the phosphorylation of ERK and AKT, increased Bcl-2 expression and inhibited caspase-3 activation in CUMS mice. Interestingly, HMW FGF-2 enhanced the activity of the brain-derived neurotrophic factor (BDNF) to a greater extent than did LMW FGF-2 in the hippocampus. Taken together, these results suggest that depressive symptoms can be relieved by administering different forms of FGF-2 peripherally in a CUMS-induced depression model through a similar antidepressant signaling pathway, therefore suggesting a potential clinical use for FGF-2 as a treatment for depression.

Inhibition of Autophagy in Microglia Alters Depressive-Like Behavior via BDNF Pathway in Postpartum Depression

Postpartum depression (PPD) is associated with mood disorders and elevated inflammation. Studies have evidenced the activation/inhibition of autophagy and excessive activation of microglia to have a close relationship with depression. C57 and microglia-specific autophagy-deficient mice (Cx3Cr1Cre/+ATG5loxp/loxp) were employed to establish the chronic unpredicted mild stress depression mice model from embryonic day 7 (E7) to embryonic day 16 (E16). Fluoxetine was administered for 3 weeks (commencing from 1 week after birth). Behavioral tests (open field, forced swimming, and sucrose preference tests) were implemented. Western blot and immunofluorescence staining were employed to assess the brain-derived neurotrophic factor (BDNF) expression level, autophagy-associated proteins, and inflammatory factors. Depressive behavior was reversed following fluoxetine treatment; this was evidenced via open field, sucrose preference, and forced swimming tests. Both BDNF and autophagy-associated proteins (ATG5, Beclin-1, and LC3II) were upregulated following fluoxetine treatment. Inflammatory factors including nuclear factor kappa B and inducible nitric oxide synthase were reduced while anti-inflammatory factor interleukin-10 (IL-10) was increased after fluoxetine treatment. Microglia-specific autophagy-deficient mice (Cx3Cr1Cre/+ATG5loxp/loxp) showed a curtailed autophagy level, higher inflammatory level, and reduced BDNF expression when compared with C57 mice. Autophagy inhibition in microglia contributes to inflammation, which further instigates PPD. Fluoxetine might mediate its antidepressant effect in PPD through the autophagic pathway while upregulating BDNF expression. In view of this, regulating BDNF in microglia is a potential novel therapy target for PPD.

Regulation of MicroRNAs-Mediated Autophagic Flux: A New Regulatory Avenue for Neurodegenerative Diseases With Focus on Prion Diseases

Prion diseases are fatal neurological disorders affecting various mammalian species including humans. Lack of proper diagnostic tools and non-availability of therapeutic remedies are hindering the control strategies for prion diseases. MicroRNAs (miRNAs) are abundant endogenous short non-coding essential RNA molecules that negatively regulate the target genes after transcription. Several biological processes depend on miRNAs, and altered profiles of these miRNAs are potential biomarkers for various neurodegenerative diseases, including prion diseases. Autophagic flux degrades the misfolded prion proteins to reduce chronic endoplasmic reticulum stress and enhance cell survival. Recent evidence suggests that specific miRNAs target and regulate the autophagic mechanism, which is critical for alleviating cellular stress. miRNAs-mediated regulation of these specific proteins involved in the autophagy represents a new target with highly significant therapeutic prospects. Here, we will briefly describe the biology of miRNAs, the use of miRNAs as potential biomarkers with their credibility, the regulatory mechanism of miRNAs in major neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and prion diseases, degradation pathways for aggregated prion proteins, the role of autophagy in prion diseases. Finally, we will discuss the miRNAs-modulated autophagic flux in neurodegenerative diseases and employ them as potential therapeutic intervention strategy in prion diseases.

Pre-reproductive stress and fluoxetine treatment in rats affect offspring A-to-I RNA editing, gene expression and social behavior

Adenosine to inosine RNA editing is an epigenetic process that entails site-specific modifications in double-stranded RNA molecules, catalyzed by adenosine deaminases acting on RNA (ADARs). Using the multiplex microfluidic PCR and deep sequencing technique, we recently showed that exposing adolescent female rats to chronic unpredictable stress before reproduction affects editing in the prefrontal cortex and amygdala of their newborn offspring, particularly at the serotonin receptor 5-HT2c (encoded by Htr2c). Here, we used the same technique to determine whether post-stress, pre-reproductive maternal treatment with fluoxetine (5 mg/kg, 7 days) reverses the effects of stress on editing. We also examined the mRNA expression of ADAR enzymes in these regions, and asked whether social behavior in adult offspring would be altered by maternal exposure to stress and/or fluoxetine. Maternal treatment with fluoxetine altered Htr2c editing in offspring amygdala at birth, enhanced the expression of Htr2c mRNA and RNA editing enzymes in the prefrontal cortex, and reversed the effects of pre-reproductive stress on Htr2c editing in this region. Furthermore, maternal fluoxetine treatment enhanced differences in editing of glutamate receptors between offspring of control and stress-exposed rats, and led to enhanced social preference in adult offspring. Our findings indicate that pre-gestational fluoxetine treatment affects patterns of RNA editing and editing enzyme expression in neonatal offspring brain in a region-specific manner, in interaction with pre-reproductive stress. Overall, these findings imply that fluoxetine treatment affects serotonergic signaling in offspring brain even when treatment is discontinued before gestation, and its effects may depend upon prior exposure to stress.

Hippocampal MicroRNAs Respond to Administration of Antidepressant Fluoxetine in Adult Mice

Current antidepressant treatments to anxiety and depression remain inadequate, burdened by a significant percentage of misuse and drug side-effects, due to unclear mechanisms of actions of antidepressants. To better understand the regulatory roles of antidepressant fluoxetine-related drug reactions, we here investigate changes of expression levels of hippocampal microRNAs (miRNAs) after administration of fluoxetine in normal adult mice. We find that 64 miRNAs showed significant changes between fluoxetine treatment and control groups by analyzing 626 mouse miRNAs. Many miRNAs in response to fluoxetine are involved in neural-related signaling pathways by analyzing miRNA-target gene pairs using the Kyoto encyclopedia of genes and genomes (KEGG) and Gene Ontology (GO). Moreover, miRNAs with altered expression are mainly associated with the repression of the dopaminergic synapse signals, which may affect hippocampal function after fluoxetine treatment. Our results demonstrate that a number of miRNAs respond to antidepressants even in normal mice and may affect target gene expression, which supports the safety consideration of inappropriate treatment and off-label use of antidepressant drugs.

Fluoxetine induces autophagic cell death via eEF2K-AMPK-mTOR-ULK complex axis in triple negative breast cancer

OBJECTIVES

Triple negative breast cancer (TNBC) is a complex and intrinsically aggressive tumour with poor prognosis, and the discovery of targeted small-molecule drugs for TNBC treatment still remains in its infancy. In this study, we aimed to discover a small-molecule agent for TNBC treatment and illuminate its potential mechanisms.

MATERIALS AND METHODS

Cell viability was detected by using methylthiazoltetrazolium (MTT) assay. Electron microscopy, GFP-LC3 transfection, monodansylcadaverine staining and apoptosis assay were performed to determine Fluoxetine-induced autophagy and apoptosis. Western blotting and siRNA transfection were carried out to investigate the mechanisms of Fluoxetine-induced autophagy. iTRAQ-based proteomics analysis was used to explore the underlying mechanisms.

RESULTS

We have demonstrated that Fluoxetine had remarkable anti-proliferative activities and induced autophagic cell death in MDA-MB-231 and MDA-MB-436 cells. The mechanism for Fluoxetine-induced autophagic cell death was associated with inhibition of eEF2K and activation of AMPK-mTOR-ULK complex axis. Further iTRAQ-based proteomics and network analyses revealed that Fluoxetine-induced mechanism was involved in BIRC6, BNIP1, SNAP29 and Bif-1.

CONCLUSIONS

These results demonstrate that Fluoxetine induces apoptosis and autophagic cell death in TNBC, which will hold a promise for the future TNBC therapy.