Morphine regulates Argonaute 2 and TH expression and activity but not miR-133b in midbrain dopaminergic neurons

Transcriptomic Profile of the Male Rat Hypothalamus and Nucleus Accumbens After Paroxetine Treatment and Withdrawal: Possible Causes of Sexual Dysfunction

Paroxetine, a selective serotonin reuptake inhibitor (SSRI), may induce sexual dysfunction during treatment and upon discontinuation. The mechanisms involved have been poorly explored so far. We have analyzed, by RNA sequencing, the whole transcriptomic profile in the hypothalamus and nucleus accumbens (NAc) (two brain regions involved in sexual behavior) of male rats daily treated for 2 weeks with paroxetine (T0) and at 1 month of withdrawal (T1). Data here reported show seven differentially expressed genes (DEGs) at T0 and 1 at T1 in the hypothalamus and 245 at T0 and 6 at T1 in the NAc. In addition, Gene-Set Enrichment, Gene Ontology, and Reactome analyses confirm that inflammatory signature and immune system activation were present at T0 in both brain areas. Considering that inflammation is generally associated with depression and that no paradigms inducing the pathology were here applied, these SSRI pro-depressive effects should be considered in patients without a clear indication of depression. Moreover, DEGs related to neurotransmitters with a role in sexual behavior and the reward system, such as dopamine (e.g., sialyltransferase 8B-ST8SIA3), glutamate (e.g., glutamate receptor ionotropic delta-2-GRID2) and GABA (e.g., glutamate decarboxylase type 2-GAD2) or associated with neurexin and neuroligin pathways and brain-derived neurotrophic factor (BDNF) signaling, were reported to be dysregulated in the NAc, further confirming dysfunction in this brain area. Interestingly, the analysis of DEGs altered at T1 in the NAc confirms the persistence of some of these side effects providing further information for post-SSRI sexual dysfunction (PSSD) etiopathogenesis.

Dysregulation of MicroRNA Biogenesis Machinery in Nervous System Diseases

MicroRNAs (miRNAs) have become essential modulators in many brain disorders, such as neurodegenerative diseases, psychiatry disorders, and chronic pain syndromes, and they play a critical role in controlling gene expression. This review investigates how disorders of the nervous system and pain research are affected by malfunctions in the miRNA biogenesis machinery. Despite tremendous progress, we still do not fully understand how these molecular regulators affect neuropathological processes. Even with the increasing amount of research, little is known about the malfunctions of the miRNA machinery, especially when it comes to the nervous system and the diseases that are linked to it. The results of recent research are compiled in this review, which emphasizes the role that disruptions in miRNA processing enzymes, including Drosha, Dicer, Argonaute, and RISC proteins, play in neurological conditions like Parkinson's and Alzheimer's diseases, as well as more general neurodegeneration. We also go over current studies on the stimulus-dependent, temporal, and spatial expression patterns of these essential miRNA biogenesis components in pain. These discoveries broaden our knowledge of the fundamental processes behind pain-related illnesses and present prospective directions for focused therapeutic approaches.

Repeated Use of Morphine Induces Anxiety by Affecting a Proinflammatory Cytokine Signaling Pathway in the Prefrontal Cortex in Rats

We examined the role of toll-like receptors (TLRs) and proinflammatory cytokine signaling pathways in the prefrontal cortex (PFC) in anxiety-like behaviors after repeated use of morphine. Morphine (10 mg/kg) was used twice daily for 8 days to induce morphine dependence in male Wistar rats. On day 8, opioid dependence was confirmed by measuring naloxone-precipitated withdrawal signs. On days 1 and 8, anxiety-like behaviors were evaluated using a light/dark box test. Expression of TLR1 and 4, proinflammatory cytokines, and some of the downstream signaling molecules was also evaluated in the bilateral PFC at mRNA and protein levels following morphine dependence. The results revealed that morphine caused anxiolytic-like effects on day 1 while induced anxiety following 8 days of repeated injection. On day 8, a significant decrease in TLR1 expression was detected in the PFC in morphine-dependent rats, but TLR4 remained unaffected. Repeated morphine injection significantly increased IL1-β, TNFα, and IL6 expression, but decreased IL1R and TNFR at mRNA and protein levels except for IL6R at the protein level in the PFC. The p38α mitogen-activated protein (MAP) kinase expression significantly increased but the JNK3 expression decreased in the PFC in morphine-dependent rats. Repeated injection of morphine also significantly increased the NF-κB expression in the PFC. Further, significant increases in Let-7c, mir-133b, and mir-365 were detected in the PFC in morphine-dependent rats. We conclude that TLR1 and proinflammatory cytokines signaling pathways in the PFC are associated with the anxiogenic-like effects of morphine following its chronic use in rats via a MAP kinase/NF-κB pathway.

Role of nucleus accumbens microRNA-181a and MeCP2 in incubation of heroin craving in male rats

RATIONALE

Epigenetic regulation has been implicated in the incubation of drug craving (the time-dependent increase in drug seeking after prolonged withdrawal from drug self-administration). There is little information available on the role of microRNAs in incubation of heroin craving.

OBJECTIVE

This study aimed to investigate the roles and mechanisms of miR-181a and methyl CpG binding protein 2 (MeCP2) in the nucleus accumbens (NAc) in incubation of heroin seeking.

METHODS

MiRNA sequencing was used to predict potential miRNAs, and miRNA profiles were performed in the NAc after 1 day or 14 days after withdrawal from heroin self-administration. Following 14 days of heroin self-administration, rats were injected of lentiviral vectors into the NAc and evaluated for the effects of overexpression of miR-181a or knockdown of MeCP2 on non-reinforced heroin seeking after 14 withdrawal days.

RESULTS

Lever presses during the heroin-seeking tests were higher after 14 withdrawal days than after 1 day (incubation of heroin craving). miR-181a expression in NAc was lower after 14 withdrawal days than after 1 day, and meCP2 expression in NAc was higher after 14 days than after 1 day. Luciferase activity assay showed that the 3'UTR of MeCP2 is directly regulated by miR-181a. Overexpression of miR-181a in NAc decreased heroin seeking after 14 withdrawal days and decreased MeCP2 mRNA and protein expression. Knockdown of MeCP2 expression in NAc by LV-siRNA-MeCP2 also decreased heroin seeking after 14 withdrawal days.

CONCLUSIONS

Results indicate that incubation of heroin craving is mediated in part by time-dependent decreases in NAc miR181a expression that leads to time-dependent increases in MeCP2 expression. Our data suggest that NAc miR-181a and MeCP2 contribute to incubation of heroin craving.

AddictGene: An integrated knowledge base for differentially expressed genes associated with addictive substance

Addiction, a disorder of maladaptive brain plasticity, is associated with changes in numerous gene expressions. Nowadays, high-throughput sequencing data on addictive substance-induced gene expression have become widely available. A resource for comprehensive annotation of genes that show differential expression in response to commonly abused substances is necessary. So, we developed AddictGene by integrating gene expression, gene-gene interaction, gene-drug interaction and epigenetic regulatory annotation for over 70,156 items of differentially expressed genes associated with 7 commonly abused substances, including alcohol, nicotine, cocaine, morphine, heroin, methamphetamine, and amphetamine, across three species (human, mouse, rat). We also collected 1,141 addiction-related experimentally validated genes by techniques such as RT-PCR, northern blot and in situ hybridization. The easy-to-use web interface of AddictGene (http://159.226.67.237/sun/addictgedb/) allows users to search and browse multidimensional data on DEGs of their interest: 1) detailed gene-specific information extracted from the original studies; 2) basic information about the specific gene extracted from NCBI; 3) SNP associated with substance dependence and other psychiatry disorders; 4) expression alteration of specific gene in other psychiatric disorders; 5) expression patterns of interested gene across 31 primary and 54 secondary human tissues; 6) functional annotation of interested gene; 7) epigenetic regulators involved in the alteration of specific genes, including histone modifications and DNA methylation; 8) protein-protein interaction for functional linkage with interested gene; 9) drug-gene interaction for potential druggability. AddictGene offers a valuable repository for researchers to study the molecular mechanisms underlying addiction, and might provide valuable insights into potential therapies for drug abuse and relapse.

Circular RNA expression profiling in the nucleus accumbens: Effects of electroacupuncture treatment on morphine-induced conditioned place preference

Electroacupuncture (EA) has been developed on the basis of traditional Chinese acupuncture. EA can suppress craving in opioid addicts and opioid-seeking responses in rodents. However, the molecular mechanism of EA on the rewarding properties of morphine and craving responses is not known. Here, we have applied a conditioned place preference paradigm in mice to measure morphine-induced rewarding effects along with EA treatment. Circular RNAs (circRNAs) can function as micro RNA (miRNA) sponges to effectively regulate gene expression levels. CircRNA profiling within the nucleus accumbens (NAc) was performed in EA-treated and sham-treated mice. Following RNAseq, data were analyzed by gene ontology (GO) and Kyoto Encyclopedia Genes and Genomes (KEGG) tools. We identified 112 significantly differentially expressed circRNAs, including 51 that were up-regulated and 61 that were down-regulated. Our bioinformatics analyses show that these differentially expressed circRNAs map into pathways that are mainly involved with renin secretion and the cGMP-PKG signaling. We further constructed a circRNA-miRNA network that predicts the potential roles of the differentially expressed circRNAs and the interaction of circRNAs with miRNAs. Our secondary sequencing and bioinformatics analysis in the NAc after EA treatment on morphine-induced CPP provides putative novel targets on molecular mechanisms involved in morphine reinforcement and possibly craving.

Epigenetic Mechanisms of Opioid Addiction

Opioid use kills tens of thousands of Americans each year, devastates families and entire communities, and cripples the health care system. Exposure to opioids causes long-term changes to brain regions involved in reward processing and motivation, leading vulnerable individuals to engage in pathological drug seeking and drug taking that can remain a lifelong struggle. The persistence of these neuroadaptations is mediated in part by epigenetic remodeling of gene expression programs in discrete brain regions. Although the majority of work examining how epigenetic modifications contribute to addiction has focused on psychostimulants such as cocaine, research into opioid-induced changes to the epigenetic landscape is emerging. This review summarizes our knowledge of opioid-induced epigenetic modifications and their consequential changes to gene expression. Current evidence points toward opioids promoting higher levels of permissive histone acetylation and lower levels of repressive histone methylation as well as alterations to DNA methylation patterns and noncoding RNA expression throughout the brain's reward circuitry. Additionally, studies manipulating epigenetic enzymes in specific brain regions are beginning to build causal links between these epigenetic modifications and changes in addiction-related behavior. Moving forward, studies must leverage advanced chromatin analysis and next-generation sequencing approaches combined with bioinformatics pipelines to identify novel gene networks regulated by particular epigenetic modifications. Improved translational relevance also requires increased focus on volitional drug-intake models and standardization of opioid exposure paradigms. Such work will significantly advance our understanding of how opioids cause persistent changes to brain function and will provide a platform on which to develop interventions for treating opioid addiction.

Novel biomarkers to assess in utero effects of maternal opioid use: First steps toward understanding short- and long-term neurodevelopmental sequelae

Maternal opioid use disorder is common, resulting in significant neonatal morbidity and cost. Currently, it is not possible to predict which opioid-exposed newborns will require pharmacotherapy for neonatal abstinence syndrome. Further, little is known regarding the effects of maternal opioid use disorder on the developing human brain. We hypothesized that novel methodologies utilizing fetal central nervous system-derived extracellular vesicles isolated from maternal blood can address these gaps in knowledge. Plasma from opioid users and controls between 9 and 21 weeks was precipitated and extracellular vesicles were isolated. Mu opioid and cannabinoid receptor levels were quantified. Label-free proteomics studies and unbiased small RNA next generation sequencing was performed in paired fetal brain tissue. Maternal opioid use disorder increased mu opioid receptor protein levels in extracellular vesicles independent of opioid equivalent dose. Moreover, cannabinoid receptor levels in extracellular vesicles were upregulated with opioid exposure indicating cross talk with endocannabinoids. Maternal opioid use disorder was associated with significant changes in extracellular vesicle protein cargo and fetal brain micro RNA expression, especially in male fetuses. Many of the altered cargo molecules and micro RNAs identified are associated with adverse clinical neurodevelopmental outcomes. Our data suggest that assays relying on extracellular vesicles isolated from maternal blood extracellular vesicles may provide information regarding fetal response to opioids in the setting of maternal opioid use disorder. Prospective clinical studies are needed to evaluate the association between extracellular vesicle biomarkers, risk of neonatal abstinence syndrome and neurodevelopmental outcomes.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

MicroRNAs regulate synaptic plasticity underlying drug addiction

Chronic use of drugs of abuse results in neurochemical, morphological and behavioral plasticity that underlies the emergence of compulsive drug seeking and vulnerability to relapse during periods of attempted abstinence. Identifying and reversing addiction-relevant plasticity is seen as a potential point of pharmacotherapeutic intervention in drug-addicted individuals. Despite considerable advances in our understanding of the actions of drugs of abuse in the brain, this information has thus far yielded few novel treatment options addicted individuals. MicroRNAs are small noncoding RNAs that can each regulate the translation of hundreds to thousands of messenger RNAs. The highly pleiotropic nature of miRNAs has focused attention on their contribution to addiction-relevant structural and functional plasticity in the brain and their potential utility as targets for medications development. In this review, we discuss the roles of miRNAs in synaptic plasticity underlying the development of addiction and then briefly discuss the possibility of using circulating miRNA as biomarkers for addiction.

MiR-218 targets MeCP2 and inhibits heroin seeking behavior

MicroRNAs (miRNAs) are a class of evolutionarily conserved, 18-25 nucleotide non-coding sequences that post-transcriptionally regulate gene expression. Recent studies implicated their roles in the regulation of neuronal functions, such as learning, cognition and memory formation. Here we report that miR-218 inhibits heroin-induced behavioral plasticity. First, network propagation-based method was used to predict candidate miRNAs that played potential key roles in regulating drug addiction-related genes. Microarray screening was also carried out to identify miRNAs responding to chronic heroin administration in the nucleus accumbens (NAc). Among the collapsed miRNAs, top-ranked miR-218 was decreased after chronic exposure to heroin. Lentiviral overexpression of miR-218 in NAc could inhibit heroin-induced reinforcement in both conditioned place preference (CPP) test and heroin self-administration experiments. Luciferase activity assay indicated that miR-218 could regulate 3' untranslated regions (3' UTR) of multiple neuroplasticity-related genes and directly target methyl CpG binding protein 2 (Mecp2). Consistently, Mecp2^308/y mice exhibited reduced heroin seeking behavior in CPP test. These data reveal a functional role of miR-218 and its target, MeCP2, in the regulation of heroin-induced behavioral plasticity.

Maternal Separation Impairs Cocaine-Induced Behavioural Sensitization in Adolescent Mice

Adverse early-life conditions induce persistent disturbances that give rise to negative emotional states. Therefore, early life stress confers increased vulnerability to substance use disorders, mainly during adolescence as the brain is still developing. In this study, we investigated the consequences of maternal separation, a model of maternal neglect, on the psychotropic effects of cocaine and the neuroplasticity of the dopaminergic system. Our results show that mice exposed to maternal separation displayed attenuated behavioural sensitization, while no changes were found in the rewarding effects of cocaine in the conditioned place preference paradigm and in the reinforcing effects of cocaine in the self-administration paradigm. The evaluation of neuroplasticity in the striatal dopaminergic pathways revealed that mice exposed to maternal separation exhibited decreased protein expression levels of D2 receptors and increased levels of the transcriptional factor Nurr1. Furthermore, animals exposed to maternal separation and treated with cocaine exhibited increased DA turnover and protein expression levels of DAT and D2R, while decreased Nurr1 and Pitx3 protein expression levels were observed when compared with saline-treated mice. Taken together, our data demonstrate that maternal separation caused an impairment of cocaine-induced behavioural sensitization possibly due to a dysfunction of the dopaminergic system, a dysfunction that has been proposed as a factor of vulnerability for developing substance use disorders.

Different contribution of glucocorticoids in the basolateral amygdala to the formation and expression of opiate withdrawal-associated memories

Drug-withdrawal aversive memories generate a motivational state leading to compulsive drug taking, with plasticity changes in the basolateral amygdala (BLA) being essential in aversive motivational learning. The conditioned-place aversion (CPA) paradigm allows for measuring the negative affective component of drug withdrawal. First, CPA triggers association between negative affective consequences of withdrawal with context (memory consolidation). Afterwards, when the animals are re-exposed to the paired environment, they avoid it due to the association between the context and aversive memories (memory retrieval). We examined the influence of glucocorticoids (GCs) for a morphine-withdrawal CPA paradigm, along with plasticity changes in the BLA, in sham-operated and adrenalectomized (ADX) animals. We demonstrated that sham+morphine animals robustly displayed CPA, whereas ADX-dependent animals lacked the affective-like signs of opiate withdrawal but displayed increased somatic signs of withdrawal. Glucocorticoid receptor (GR) actions promote memory consolidation but highly depend on increases in GC levels. Interestingly, we observed that GCs were only increased in sham-dependent rodents during aversive-withdrawal memory consolidation, and that GR expression correlated with phosphorylated cAMP response element binding (pCREB) protein, early growth response 1 (Egr-1) and activity-regulated cytoskeletal-associated (Arc) mRNA induction in this experimental group. In contrast, ADX-animals displayed reduced (pCREB). GCs are also known to impair memory retrieval. Accordingly, we showed that GCs levels remained at basal levels in all experimental groups following memory retrieval, and consequently GRs no longer acted as transcriptional regulators. Importantly, memory retrieval elicited increased pCREB levels in sham+morphine animals (not in ADX+morphine group), which were directly correlated with enhanced Arc mRNA/protein expression mainly in glutamatergic neurons. In conclusion, context-withdrawal associations are accompanied plasticity changes in the BLA, which are, in part, regulated by GR signaling. Moreover, dysregulation of CREB signaling, in part through Arc expression, may enhance reconsolidation, resulting in the maintenance of excessive aversive states. These findings might have important implications for drug-seeking behavior.

miR-181a is a negative regulator of GRIA2 in methamphetamine-use disorder

A previous study reported that the miR-181a level in serum was significantly different between patients with methamphetamine-use disorder and healthy controls and that chronic methamphetamine use down-regulates the expression of miR-181a. Bioinformatic analysis predicted that miR-181a might bind the 3′-UTRs of the mRNA transcripts of the human glutamate receptor genes GRIA2 and GABRA1. In this study, we measured the expression of GRIA2 and GABRA1 in patients with methamphetamine-use disorder. In addition, we examined whether miR-181a down-regulates GRIA2 and GABRA1 in a cell-based assay. We further examined the effects of chronic methamphetamine exposure on the expression of miR-181a, GRIA2 and GABRA1. The results demonstrated that serum GRIA2 is higher in patients with methamphetamine-use disorder than in healthy controls. Dual luciferase reporter assays and a cell-based model of methamphetamine exposure also showed that miR-181a directly regulates expression of GRIA2. This study supports the evidence that miR-181a and the glutamate AMPA receptor gene GRIA2 play a critical role in methamphetamine-use disorder.

Glucocorticoid Homeostasis in the Dentate Gyrus Is Essential for Opiate Withdrawal-Associated Memories

Drug-withdrawal-associated aversive memories might trigger relapse to drug-seeking behavior. However, changes in structural and synaptic plasticity, as well as epigenetic mechanisms, which may be critical for long-term aversive memory, have yet to be elucidated. We used male Wistar rats and performed conditioned-place aversion (CPA) paradigm to uncover the role of glucocorticoids (GCs) on plasticity-related processes that occur within the dentate gyrus (DG) during opiate-withdrawal conditioning (memory formation-consolidation) and after reactivation by re-exposure to the conditioned environment (memory retrieval). Rats subjected to conditioned morphine-withdrawal robustly expressed CPA, while adrenalectomy impaired naloxone-induced CPA. Importantly, while activity-regulated cytoskeletal-associated protein (Arc) expression was induced in sham- and ADX-dependent animals during the conditioning phase, Arc and early growth response 1 (Egr-1) induction was restricted to sham-dependent rats following memory retrieval. Moreover, we found a correlation between Arc induction and CPA score, and Arc was selectively expressed in the granular zone of the DG in dopaminoceptive, glutamatergic and GABAergic neurons. We further found that brain-derived neurotrophic factor was regulated in the opposite way during the test phase. Our results also suggest a role for epigenetic regulation on the expression of glucocorticoid receptors and Arc following memory retrieval. Our data provide the first evidence that GC homeostasis is important for the expression of long-term morphine-withdrawal memories. Moreover, our results support the idea that targeting Arc and Egr-1 in the DG may provide important insights into the role of these signaling cascades in withdrawal-context memory re-consolidation. Together, disrupting these processes in the DG might lead to effective treatments in drug addiction thereby rapidly and persistently reducing invasive memories and subsequent drug seeking.

Adenovirus-mediated expression of orphan nuclear receptor NR4A2 targeting hepatic stellate cell attenuates liver fibrosis in rats

Liver fibrosis is a wound-healing response characterized with the accumulation of extracellular matrix (ECM). And hepatic stellate cells (HSCs) are the principal cell source of ECM. NR4A2 (Nurr1) is a member of orphan nuclear receptor NR4A family and acts as transcription factor. It participates in regulating cell differentiation, proliferation and apoptosis. We previously demonstrated that NR4A2 expression in fibrotic liver reduced significantly compared with normal liver and NR4A2 knockout in HSCs promoted ECM production. In the present study we explored the role of NR4A2 on liver fibrosis. Studies in cultured HSCs demonstrated that NR4A2 over-expression suppressed the activation of HSCs, such as ECM production and invasion ability. Moreover cell cycle was arrested, cell apoptosis was promoted and cell signaling pathway was influenced. Adenovirus-mediated delivery of NR4A2 in rats ameliorated significantly dimethylnitrosamine (DMN) induced liver fibrosis. The In vivo experiments produced results consistent with in vitro experiments. Taken together these results demonstrate NR4A2 enhancement attenuates liver fibrosis via suppressing the activation of HSCs and NR4A2 may be an ideal target for anti-fibrotic therapy.

μ Opioid Receptor Expression after Morphine Administration Is Regulated by miR-212/132 Cluster

Since their discovery, miRNAs have emerged as a promising therapeutical approach in the treatment of several diseases, as demonstrated by miR-212 and its relation to addiction. Here we prove that the miR-212/132 cluster can be regulated by morphine, through the activation of mu opioid receptor (Oprm1). The molecular pathways triggered after morphine administration also induce changes in the levels of expression of oprm1. In addition, miR-212/132 cluster is actively repressing the expression of mu opioid receptor by targeting a sequence in the 3’ UTR of its mRNA. These findings suggest that this cluster is closely related to opioid signaling, and function as a post-transcriptional regulator, modulating morphine response in a dose dependent manner. The regulation of miR-212/132 cluster expression is mediated by MAP kinase pathway, CaMKII-CaMKIV and PKA, through the phosphorylation of CREB. Moreover, the regulation of both oprm1 and of the cluster promoter is mediated by MeCP2, acting as a transcriptional repressor on methylated DNA after prolonged morphine administration. This mechanism explains the molecular signaling triggered by morphine as well as the regulation of the expression of the mu opioid receptor mediated by morphine and the implication of miR-212/132 in these processes.

Regulation of dopaminergic markers expression in response to acute and chronic morphine and to morphine withdrawal

Dopamine (DA) is thought to represent a teaching signal and has been implicated in the induction of addictive behaviours. Dysfunction of DA homeostasis leading to high or low DA levels is causally linked to addiction. Previously, it has been proposed that the transcription factors Nurr1 and Pitx3, which are critical for transcription of a set of genes involved in DA metabolism in the mesolimbic pathway, are associated with addiction pathology. Using quantitative real-time polymerase chain reaction, immunofluorescence and Western blotting, we studied the effects of single morphine administration, morphine dependence and withdrawal on the DA markers DA transporters (DAT), vesicular monoamine transporters (VMAT2) and DA 2 receptor subtype (DRD2), DA 1 receptor subtype as well as tyrosine hydroxylase (TH) in the ventral tegmental area (VTA) and/or nucleus accumbens (NAc). In addition, Nurr1 and Pitx3 expression was also measured. Present data showed a high degree of colocalization of Nurr1 and Pitx3 with TH(+) neurons in the VTA. We found that the increased Nurr1 and/or Pitx3 levels during morphine dependence and in morphine-withdrawn rats were associated to an increase of DAT, VMAT2 and DRD2. Altogether, present data indicate that morphine dependence and withdrawal induced consistent alterations of most of the DA markers, which was correlated with transcription factors involved in the maintenance of DA neurons in drug-reward pathways, suggesting that Nurr1 and Pitx3 regulation might be associated with controlling adaptation to chronic morphine and to morphine withdrawal-induced alterations of DA neurons activity in the mesolimbic pathway.

Orphan nuclear receptor NR4A2 inhibits hepatic stellate cell proliferation through MAPK pathway in liver fibrosis

Hepatic stellate cells (HSCs) play a crucial role in liver fibrosis, which is a pathological process characterized by extracellular matrix accumulation. NR4A2 is a nuclear receptor belonging to the NR4A subfamily and vital in regulating cell growth, metabolism, inflammation and other biological functions. However, its role in HSCs is unclear. We analyzed NR4A2 expression in fibrotic liver and stimulated HSCs compared with control group and studied the influence on cell proliferation, cell cycle, cell apoptosis and MAPK pathway after NR4A2 knockdown. NR4A2 expression was examined by real-time polymerase chain reaction, Western blotting, immunohistochemistry and immunofluorescence analyses. NR4A2 expression was significantly lower in fibrotic liver tissues and PDGF BB or TGF-β stimulated HSCs compared with control group. After NR4A2 knockdown α-smooth muscle actin and Col1 expression increased. In addition, NR4A2 silencing led to the promotion of cell proliferation, increase of cell percentage in S phase and reduced phosphorylation of ERK1/2, P38 and JNK in HSCs. These results indicate that NR4A2 can inhibit HSC proliferation through MAPK pathway and decrease extracellular matrix in liver fibrogenesis. NR4A2 may be a promising therapeutic target for liver fibrosis.

Roles of the canonical myomiRs miR-1, -133 and -206 in cell development and disease

MicroRNAs are small non-coding RNAs that participate in different biological processes, providing subtle combinational regulation of cellular pathways, often by regulating components of signalling pathways. Aberrant expression of miRNAs is an important factor in the development and progression of disease. The canonical myomiRs (miR-1, -133 and -206) are central to the development and health of mammalian skeletal and cardiac muscles, but new findings show they have regulatory roles in the development of other mammalian non-muscle tissues, including nerve, brain structures, adipose and some specialised immunological cells. Moreover, the deregulation of myomiR expression is associated with a variety of different cancers, where typically they have tumor suppressor functions, although examples of an oncogenic role illustrate their diverse function in different cell environments. This review examines the involvement of the related myomiRs at the crossroads between cell development/tissue regeneration/tissue inflammation responses, and cancer development.

Morphine Promotes Astrocyte-Preferential Differentiation of Mouse Hippocampal Progenitor Cells via PKCε-Dependent ERK Activation and TRBP Phosphorylation

Previously we have shown that morphine regulates adult neurogenesis by modulating miR-181a maturation and subsequent hippocampal neural progenitor cell (NPC) lineages. Using NPCs cultured from PKCε or β-arrestin2 knockout mice and the MAPK/ERK kinase inhibitor U0126, we demonstrate that regulation of NPC differentiation via the miR-181a/Prox1/Notch1 pathway exhibits ligand-dependent selectivity. In NPCs, morphine and fentanyl activate ERK via the PKCε- and β-arrestin-dependent pathways, respectively. After fentanyl exposure, the activated phospho-ERK translocates to the nucleus. Conversely, after morphine treatment, phospho-ERK remains in the cytosol and is capable of phosphorylating TAR RNA-binding protein (TRBP), a cofactor of Dicer. This augments Dicer activity and promotes the maturation of miR-181a. Furthermore, using NPCs transfected with wild-type TRBP, SΔA, and SΔD TRBP mutants, we confirmed the crucial role of TRBP phosphorylation in Dicer activity, miR-181a maturation, and finally the morphine-induced astrocyte-preferential differentiation of NPCs. Thus, morphine modulates the lineage-specific differentiation of NPCs by PKCε-dependent ERK activation with subsequent TRBP phosphorylation and miR-181a maturation.

Dysregulation of dopaminergic regulatory mechanisms in the mesolimbic pathway induced by morphine and morphine withdrawal

Dopamine (DA) is thought to represent a teaching signal and has been implicated in the induction of addictive behaviours. Previously, it has been proposed that the transcription factors Nurr1 and Pitx3, which are critical for transcription of a set of genes involved in DA metabolism in the mesolimbic pathway, are associated with addiction pathology. The aim of our study was to investigate abnormalities in the mesolimbic pathway associated with morphine dependence and withdrawal. Using quantitative real-time PCR, immunofluorescence, HPLC and Western blotting, here we studied the effects of single morphine administration, morphine dependence and morphine withdrawal on Nurr1 and Pitx3 expression as well as on the DA marker tyrosine hydroxylase (TH) and the turnover of DA in the ventral tegmental area (VTA) and/or nucleus accumbens. We showed that the three experimental conditions caused induction of Nurr1 and Pitx3 in the VTA, which correlated with changes in TH expression during chronic morphine administration. Present data also confirmed the colocalization of Nurr1 and Pitx3 with TH-positive neurons in the posterior VTA. Furthermore, during morphine dependence, Nurr1 was detected in the nucleus compartment of VTA TH-positive neurons, whereas Pitx3 was strongly detected in the nucleus of TH-positive neurons after single morphine administration and during morphine withdrawal. The number of TH neurons, number of Nurr1 or Pitx3-positive cells, and the number of TH neurons expressing Nurr1 or Pitx3 were not modified in the subpopulations of DA neurons. Present data provide novel insight into the potential correlation between Nurr1 and Pitx3 and DA neurons plasticity during opiate addiction in the mesolimbic pathway.