RESUMO
Mortality due to opioid use has grown to the point where, for the first time in history, opioid-related deaths exceed those caused by car accidents in many states in the United States. Changes in the prescribing of opioids for pain and the illicit use of fentanyl (and derivatives) have contributed to the current epidemic. Less known is the impact of opioids on hippocampal neurogenesis, the functional manipulation of which may improve the deleterious effects of opioid use. We provide new insights into how the dysregulation of neurogenesis by opioids can modify learning and affect, mood and emotions, processes that have been well accepted to motivate addictive behaviours.
Assuntos
Afeto/efeitos dos fármacos , Analgésicos Opioides/farmacologia , Encéfalo/efeitos dos fármacos , Aprendizagem/efeitos dos fármacos , Memória/efeitos dos fármacos , Neurogênese/efeitos dos fármacos , Encéfalo/metabolismo , Humanos , Receptores Opioides/metabolismoRESUMO
Although the roles of opioid receptors in neurogenesis have been implicated in previous studies, the mechanism by which κ-opioid receptor (OPRK1) regulates adult neurogenesis remains elusive. We now demonstrate that two agonists of OPRK1, U50,488H and dynorphin A, inhibit adult neurogenesis by hindering neuronal differentiation of mouse hippocampal neural stem cells (NSCs), both in vitro and in vivo. This effect was blocked by nor-binaltorphimine (nor-BNI), a specific antagonist of OPRK1. By examining neurogenesis-related genes, we found that OPRK1 agonists were able to downregulate the expression of Pax6, Neurog2, and NeuroD1 in mouse hippocampal NSCs, in a way that Pax6 regulates the transcription of Neurog2 and Neurod1 by directly interacting with their promoters. Moreover, this effect of OPRK1 was accomplished by inducing expression of miR-7a, a miRNA that specifically targeted Pax6 by direct interaction with its 3'-UTR sequence, and thereby decreased the levels of Pax6, Neurog2, and NeuroD1, thus resulted in hindrance of neuronal differentiation of NSCs. Thus, by modulating Pax6/Neurog2/NeuroD1 activities via upregulation of miR-7a expression, OPRK1 agonists hinder the neuronal differentiation of NSCs and hence inhibit adult neurogenesis in mouse hippocampus.
Assuntos
MicroRNAs/genética , Células-Tronco Neurais/citologia , Neurogênese/genética , Fator de Transcrição PAX6/genética , Receptores Opioides kappa/genética , (trans)-Isômero de 3,4-dicloro-N-metil-N-(2-(1-pirrolidinil)-ciclo-hexil)-benzenoacetamida/farmacologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Diferenciação Celular/genética , Dinorfinas/farmacologia , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Humanos , Camundongos , Naltrexona/análogos & derivados , Naltrexona/farmacologia , Proteínas do Tecido Nervoso/genética , Neurogênese/efeitos dos fármacos , Receptores Opioides kappa/agonistas , Transdução de Sinais/efeitos dos fármacosRESUMO
We identified, via high-throughput screening using a FLIPR® calcium assay, compound 1, which incorporated a dihydroquinolinyl-2-oxoethylsulfanyl-(1H,5H)-pyrimidinedione core and activated the µ-opioid receptor (MOR) in the presence of naloxone or naltrexone. A structure-activity relationship study of the analogs of 1 led to the design of compound 21, which activated MOR in the presence of naloxone with an EC50 of 3.3 ± 0.2 µM. MOR activation by the compound 21-antagonist pair was antagonist-dependent. Compound 21 did not affect the potency of the orthosteric agonist, morphine, toward MOR, indicating that it affected the function of MOR antagonists rather than that of the agonists. Computer modeling of the compound 21-MOR-naloxone complex revealed major interactions between compound 21 and MOR, including hydrogen bonding with Ser196, π-π stacking with Tyr149, and sulfur-aromatic interaction with Trp192. This study may pave the way for developing agents capable of safe and effective MOR modulation.
Assuntos
Naloxona , Naltrexona , Analgésicos Opioides , Imidazóis , Naloxona/farmacologia , Naltrexona/farmacologia , Receptores Opioides , Sulfonamidas , TiofenosRESUMO
Opioids, like morphine and naloxone, regulate the proliferation and neuronal differentiation of neural stem cells (NSCs) in a receptor-independent and ten-eleven translocation methylcytosine dioxygenase (TET1)-dependent manner in vitro. Whether naloxone regulates hippocampal NSCs and contextual learning in vivo in a similar manner was determined. Naloxone infusion increased the Ki67 and Doublecortin positive cells in subgranular zone of wild type mice, which suggested the increased proliferation and differentiation of hippocampal NSCs in vivo and was consistent with the in vitro functions of naloxone. In addition, naloxone infusion also facilitated the contextual learning and memory of wild type mice. To determine the contribution of µ-opioid receptor (OPRM1) and TET1 to these functions of naloxone, several types of knockout mice were used. Since Tet1-/- mice have high deficiency in contextual learning and memory, Tet1+/- mice were used instead. The abilities of naloxone to regulate NSCs and to facilitate contextual learning were significantly impaired in Tet1+/- mice. In addition, these abilities of naloxone were not affected in Oprm1-/- mice. Therefore, naloxone facilitates contextual learning and memory in a receptor-independent and Tet1-dependent manner, which provides new understanding on the receptor-independent functions of opioids.
Assuntos
Proteínas de Ligação a DNA/deficiência , Aprendizagem em Labirinto/fisiologia , Memória/fisiologia , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Proteínas Proto-Oncogênicas/deficiência , Receptores Opioides mu/deficiência , Animais , Células Cultivadas , Proteínas de Ligação a DNA/genética , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Memória/efeitos dos fármacos , Camundongos , Camundongos Knockout , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/metabolismo , Proteínas Proto-Oncogênicas/genética , Receptores Opioides mu/genéticaRESUMO
It is estimated that nearly a third of people who abuse drugs started with prescription opioid medicines. Approximately, 11.5 million Americans used prescription drugs recreationally in 2016, and in 2018, 46,802 Americans died as the result of an opioid overdose, including prescription opioids, heroin, and illicitly manufactured fentanyl (National Institutes on Drug Abuse (2020) Opioid Overdose Crisis. https://www.drugabuse.gov/drugs-abuse/opioids/opioid-overdose-crisis . Accessed 06 June 2020). Yet physicians will continue to prescribe oral opioids for moderate-to-severe pain in the absence of alternative therapeutics, underscoring the importance in understanding how drug choice can influence detrimental outcomes. One of the opioid prescription medications that led to this crisis is oxycodone, where misuse of this drug has been rampant. Being one of the most highly prescribed opioid medications for treating moderate-to-severe pain as reflected in the skyrocketed increase in retail sales of 866% between 1997 and 2007, oxycodone was initially suggested to be less addictive than morphine. The false-claimed non-addictive formulation of oxycodone, OxyContin, further contributed to the opioid crisis. Abuse was often carried out by crushing the pills for immediate burst release, typically by nasal insufflation, or by liquefying the pills for intravenous injection. Here, we review oxycodone pharmacology and abuse liability as well as present the hypothesis that oxycodone may exhibit a unique pharmacology that contributes to its high likability and abuse susceptibility. We will discuss various mechanisms that likely contribute to the high abuse rate of oxycodone including clinical drug likability, pharmacokinetics, pharmacodynamics, differences in its actions within mesolimbic reward circuity compared to other opioids, and the possibility of differential molecular and cellular receptor interactions that contribute to its selective effects. We will also discuss marketing strategies and drug difference that likely contributes to the oxycodone opioid use disorders and addiction.
Assuntos
Analgésicos Opioides/efeitos adversos , Comportamento Aditivo/epidemiologia , Epidemia de Opioides , Transtornos Relacionados ao Uso de Opioides/epidemiologia , Oxicodona/efeitos adversos , Recompensa , Analgésicos Opioides/administração & dosagem , Animais , Comportamento Aditivo/psicologia , Humanos , Transtornos Relacionados ao Uso de Opioides/psicologia , Oxicodona/administração & dosagem , Dor/tratamento farmacológico , Dor/epidemiologia , Dor/psicologiaRESUMO
The abilities of opioids to activate downstream signaling pathways normally depend on the binding between opioids and their receptors. However, opioids may also function in a receptor-independent manner, especially in neural stem cells (NSCs) in which the expression of opioid receptors and endogenous opioid agonists is low. When two opioids, morphine and naloxone, were used during the early stage of NSC differentiation, increased neurogenesis was observed. However, naloxone methiodide, a membrane impenetrable analog of naloxone, did not affect the NSC differentiation. The abilities of morphine and naloxone to facilitate neurogenesis were also observed in opioid receptor-knockout NSCs. Therefore, morphine and naloxone promote neurogenesis in a receptor-independent manner at least during the early stage. In addition, the receptor-independent functions of opioids were not observed in methylcytosine dioxygenase ten-eleven translocation 1 (Tet1) knockout NSCs. When the expression of opioid receptors increased and the expression of Tet1 decreased during the late stage of NSC differentiation, morphine, but not naloxone, inhibited neurogenesis via traditional receptor-dependent and miR181a-Prox1-Notch-related pathway. In summary, the current results demonstrated the time-dependent effects of opioids during the differentiation of NSCs and provided additional insight on the complex functions of opioids.
Assuntos
Diferenciação Celular , Embrião de Mamíferos/citologia , Fibroblastos/citologia , Naloxona/farmacologia , Células-Tronco Neurais/citologia , Neurogênese , Receptores Opioides mu/fisiologia , Animais , Embrião de Mamíferos/efeitos dos fármacos , Embrião de Mamíferos/metabolismo , Feminino , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Morfina/farmacologia , Antagonistas de Entorpecentes/farmacologia , Entorpecentes/farmacologia , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/metabolismoRESUMO
M1 muscarinic acetylcholine receptors are highly expressed in key areas that control cognition, such as the cortex and hippocampus, representing one potential therapeutic target for cognitive dysfunctions of Alzheimer's disease and schizophrenia. We have reported that M1 receptors facilitate cognition by promoting membrane insertion of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor AMPA receptor subunit 1 (GluA1) through phosphorylation at Ser845. However, the signaling pathway is still unclear. Here we showed that adenylyl cyclase inhibitor 2',5'-dideoxyadenosine and PKA inhibitor KT5720 inhibited enhancement of phosphorylation of Ser845 and membrane insertion of GluA1 induced by M1 receptor activation. Furthermore, PI3K inhibitor LY294002 and protein kinase B (Akt) inhibitor IV blocked the effects of M1 receptors as well. Remarkably, the increase of the activity of PI3K-Akt signaling induced by M1 receptor activation could be abolished by cAMP-PKA inhibitors. Moreover, inhibiting the mammalian target of rapamycin (mTOR) complex 1, an important downstream effector of PI3K-Akt, by short-term application of rapamycin attenuated the effects of M1 receptors on GluA1. Furthermore, such effect was unrelated to possible protein synthesis promoted by mTOR. Taken together, these data demonstrate that M1 receptor activation induces membrane insertion of GluA1 via a signaling linking cAMP-PKA and PI3K-Akt-mTOR pathways but is irrelevant to protein synthesis.-Zhao, L.-X., Ge, Y.-H., Li, J.-B., Xiong, C.-H., Law, P.-Y., Xu, J.-R., Qiu, Y., Chen, H.-Z. M1 muscarinic receptors regulate the phosphorylation of AMPA receptor subunit GluA1 via a signaling pathway linking cAMP-PKA and PI3K-Akt.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , AMP Cíclico/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptor Muscarínico M1/metabolismo , Receptores de AMPA/metabolismo , Sistemas do Segundo Mensageiro/fisiologia , Animais , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
M1 muscarinic acetylcholine receptors (M1 mAChRs) are the most abundant muscarinic receptors in the hippocampus and have been shown to have procognitive effects. AMPA receptors (AMPARs), an important subtype of ionotropic glutamate receptors, are key components in neurocognitive networks. However, the role of AMPARs in procognitive effects of M1 mAChRs and how M1 mAChRs affect the function of AMPARs remain poorly understood. Here, we found that basal expression of GluA1, a subunit of AMPARs, and its phosphorylation at Ser845 were maintained by M1 mAChR activity. Activation of M1 mAChRs promoted membrane insertion of GluA1, especially to postsynaptic densities. Impairment of hippocampus-dependent learning and memory by antagonism of M1 mAChRs paralleled the reduction of GluA1 expression, and improvement of learning and memory by activation of M1 mAChRs was accompanied by the synaptic insertion of GluA1 and its increased phosphorylation at Ser845. Furthermore, abrogation of phosphorylation of Ser845 residue of GluA1 ablated M1 mAChR-mediated improvement of learning and memory. Taken together, these results show a functional correlation of M1 mAChRs and GluA1 and the essential role of GluA1 in M1 mAChR-mediated cognitive improvement.-Zhao, L.-X., Ge, Y.-H., Xiong, C.-H., Tang, L., Yan, Y.-H., Law, P.-Y., Qiu, Y., Chen, H.-Z. M1 muscarinic receptor facilitates cognitive function by interplay with AMPA receptor GluA1 subunit.
Assuntos
Cognição/fisiologia , Subunidades Proteicas/metabolismo , Receptor Muscarínico M1/metabolismo , Receptores de AMPA/metabolismo , Animais , Pareamento Cromossômico/fisiologia , Hipocampo/metabolismo , Aprendizagem/fisiologia , Masculino , Memória/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos/metabolismo , Fosforilação/fisiologia , Receptores Muscarínicos/metabolismoRESUMO
The use of opioid analgesics for pain has always been hampered by their many side effects; in particular, the addictive liability associated with chronic use. Recently, attempts to develop analgesic agents with reduced side effects have targeted either the putative opioid receptor splice variants or the receptor hetero-oligomers. This review discusses the potential for receptor splice variant- and the hetero-oligomer-based discovery of new opioid analgesics. We also examine an alternative approach of using receptor mutants for pain management. Finally, we discuss the role of the biased agonism observed and the recently reported opioid receptor crystal structures in guiding the future development of opioid analgesics.
Assuntos
Analgésicos/farmacologia , Receptores Opioides/química , Processamento Alternativo , Dimerização , Receptores Opioides/efeitos dos fármacos , Receptores Opioides/genéticaRESUMO
Since the discovery of µ-opioid receptor (MOR) gene two decades ago, various regulatory factors have been shown to interact with the MOR promoter and modulate transcript levels. However, the majority of early transcriptional studies on MOR gene have not addressed how intracellular signaling pathways mediate extracellular modulators. In this study, we demonstrate that MOR epigenetic regulation requires multiple coordinated signals converging at the MOR promoter, involving mitogen-activated protein kinase (MAPK) activation and mitogen- and stress-activated protein kinase 1 (MSK1)-ranges of intracellular signaling pathways similar to those activated by opioid agonists. Inhibiting p38 MAPK or extracellular signal-regulated kinase (ERK) 1/2 MAPK (upstream activators of MSK1) reduced MOR expression levels; accordingly, the functional role of MSK1, but not MSK2, was demonstrated using genetic approaches. However, for maximal MSK1 effect, an open chromatin configuration was required, because in vitro CpG methylation of the MOR promoter abolished MSK1 activity. Finally, endogenous MSK1 levels concomitantly increased to regulate MOR gene expression during neuronal differentiation of P19 cells, suggesting a conserved role of this kinase in the epigenic activation of MOR in neurons. Taken together, our findings indicate that the expression of MOR gene requires the activity of intracellular signaling pathways that have been implicated in the behavioral outcomes of opioid drugs, which suggests that an autoregulatory mechanism may function in opioid systems.
Assuntos
Epigênese Genética , Proteína Quinase 8 Ativada por Mitógeno/metabolismo , Receptores Opioides mu/genética , Acetilação/efeitos dos fármacos , Animais , Diferenciação Celular/genética , Ilhas de CpG/genética , Metilação de DNA/genética , Epigênese Genética/efeitos dos fármacos , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Inibidores de Histona Desacetilases/farmacologia , Histonas/metabolismo , Camundongos , Modelos Biológicos , Neurônios/metabolismo , Regiões Promotoras Genéticas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Fatores de Tempo , Transcrição Gênica/efeitos dos fármacos , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Expression of the mu-opioid receptor (MOR) protein is controlled by extensive transcriptional and post-transcriptional processing. MOR gene expression has previously been shown to be altered by a post-transcriptional mechanism involving the MOR mRNA untranslated region (UTR). Here, we demonstrate for the first time the role of heterogeneous nuclear ribonucleic acids (hnRNA)-binding protein (hnRNP) K and poly(C)-binding protein 1 (PCBP1) as post-transcriptional inducers in MOR gene regulation. In the absence of morphine, a significant level of MOR mRNA is sustained in its resting state and partitions in the translationally inactive polysomal fraction. Morphine stimulation activates the downstream targets hnRNP K and PCPB1 and induces partitioning of the MOR mRNA to the translationally active fraction. Using reporter and ligand binding assays, as well as RNA EMSA, we reveal potential RNP binding sites located in the 5'-untranslated region of human MOR mRNA. In addition, we also found that morphine-induced RNPs could regulate MOR expression. Our results establish the role of hnRNP K and PCPB1 in the translational control of morphine-induced MOR expression in human neuroblastoma (NMB) cells as well as cells stably expressing MOR (NMB1). J. Cell. Physiol. 232: 576-584, 2017. © 2016 Wiley Periodicals, Inc.
Assuntos
Regulação da Expressão Gênica/efeitos dos fármacos , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Ribonucleoproteínas Nucleares Heterogêneas/genética , Morfina/farmacologia , Receptores Opioides mu/metabolismo , Transcrição Gênica/efeitos dos fármacos , Regiões 5' não Traduzidas/genética , Animais , Linhagem Celular Tumoral , Proteínas de Ligação a DNA , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Ribonucleoproteínas Nucleares Heterogêneas/metabolismo , Humanos , Imunoprecipitação , Camundongos , Polirribossomos/efeitos dos fármacos , Polirribossomos/metabolismo , Ligação Proteica/efeitos dos fármacos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA , Receptores Opioides mu/genética , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/genéticaRESUMO
BACKGROUND: The authors investigated the pharmacology and signaling pathways of the opioid receptors modulated by compound 1, 1-(2,4-dibromophenyl)-3,6,6-trimethyl-1,5,6,7-tetrahydro-4H-indazol-4-one. METHODS: In vitro studies of compound 1 were assessed by using a radioligand-binding assay (n = 3), a cyclic adenosine monophosphate assay (n = 3), a ß-arrestin assay (n = 3), an internalization assay (n = 3), and an immunohistochemistry (n = 8). In vivo studies of compound 1 were characterized using a tail-flick test (n = 5 to 6), tail-clip test (n = 7), von Frey hair test (n = 5), and charcoal meal test (n = 5). RESULTS: Compound 1 elicited robust effects in µ-opioid (mean ± SD; binding affinity: 15 ± 2 nM; cyclic adenosine monophosphate assay: 24 ± 6 nM), δ-opioid (82 ± 7 nM; 1.9 ± 0.1 µM), and κ-opioid (76 ± 9 nM; 1.4 ± 0.5 µM) receptor-expressing cells. Compound 1 acts as a full agonist of ß-arrestin-2 recruitment in µ-opioid (1.1 ± 0.3 µM) and δ-opioid (9.7 ± 1.9 µM) receptor-expressing cells. Compound 1 caused less gastrointestinal dysfunction (charcoal meal test: morphine: 82 ± 5%; compound 1: 42 ± 5%) as well as better antinociception in mechanical pain hypersensitivity (tail-clip test: morphine: 10 ± 3 s; compound 1: 19 ± 1 s) and in cancer-induced pain (von Frey hair test: morphine: 0.1 ± 0.1 g; compound 1: 0.3 ± 0.1 g) than morphine at equi-antinociceptive doses. CONCLUSIONS: Compound 1 produced antinociception with less gastrointestinal dysfunction than morphine.
Assuntos
Gastroenteropatias/induzido quimicamente , Indazóis/farmacologia , Morfina , Receptores Opioides/agonistas , Analgésicos Opioides/farmacologia , Animais , Modelos Animais de Doenças , Gastroenteropatias/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos C57BLRESUMO
The development of tolerance to morphine, one of the most potent analgesics, in the management of chronic pain is a significant clinical problem and its mechanisms are poorly understood. Morphine exerts its pharmacological effects via the µ-opioid receptor (MOR). Tolerance is highly connected to G-protein-coupled receptors (GPCR) phosphorylation and desensitization increase. Because morphine desensitization previously has been shown to be MOR phosphorylation- and ß-arrestin2-independent (in contrast to agonists such as fentanyl), we examined the contribution of phosphorylation of the entire C-terminus to the development of antinociceptive tolerance to the partial (morphine) and full (fentanyl) MOR agonists in vivo. In MOR knockout (MORKO) mice, we delivered via lentivirus the genes encoding the wild-type MOR (WTMOR) or a phosphorylation-deficient MOR (Cterm(-S/T)MOR) in which all of the serine and threonine residues were mutated to alanine into the ventrolateral periaqueductal grey matter (vlPAG) or lumbar spinal cord (SC), structures that are involved in nociception. We compared the analgesic ED50 in WTMOR- and Cterm(-S/T)MOR-expressing MORKO mice before and after morphine or fentanyl tolerance was induced. Morphine acute antinociception was partially restored in WTMOR- or Cterm(-S/T)MOR-transferred MORKO mice. Fentanyl acute antinociception was observed only in MORKO mice with the transgenes expressed in the SC. Morphine antinociceptive tolerance was not affected by expressing Cterm(-S/T)MOR in the vlPAG or SC of MORKO mice. Fentanyl-induced tolerance in MORKO mice expressing WTMOR or Cterm(-S/T)MOR, is greater than morphine-induced tolerance. Thus, MOR C-terminus phosphorylation does not appear to be critical for morphine tolerance in vivo.
Assuntos
Analgésicos Opioides/farmacologia , Morfina/farmacologia , Receptores Opioides mu/metabolismo , Medula Espinal/efeitos dos fármacos , Animais , Tolerância a Medicamentos , Células HEK293 , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mutação , Receptores Opioides mu/genética , Medula Espinal/metabolismoRESUMO
Neural stem/progenitor cells (NSPCs) undergo a series of developmental processes before giving rise to newborn neurons, astrocytes and oligodendrocytes in adult neurogenesis. During the past decade, the role of NSPCs has been highlighted by studies on adult neurogenesis modulated by addictive drugs. It has been proven that these drugs regulate the proliferation, differentiation and survival of adult NSPCs in different manners, which results in the varying consequences of adult neurogenesis. The effects of addictive drugs on NSPCs are exerted via a variety of different mechanisms and pathways, which interact with one another and contribute to the complexity of NSPC regulation. Here, we review the effects of different addictive drugs on NSPCs, and the related experimental methods and paradigms. We also discuss the current understanding of major signaling molecules, especially the putative common mechanisms, underlying such effects. Finally, we review the future directions of research in this area.
Assuntos
Células-Tronco Adultas/efeitos dos fármacos , Células-Tronco Neurais/efeitos dos fármacos , Neurogênese/efeitos dos fármacos , Células-Tronco Adultas/citologia , Células-Tronco Adultas/metabolismo , Anfetamina/farmacologia , Analgésicos Opioides/farmacologia , Animais , Canabinoides/farmacologia , Proliferação de Células/efeitos dos fármacos , Estimulantes do Sistema Nervoso Central/farmacologia , Cocaína/farmacologia , Etanol/farmacologia , Estimulantes Ganglionares/farmacologia , Humanos , N-Metil-3,4-Metilenodioxianfetamina/farmacologia , Células-Tronco Neurais/citologia , Células-Tronco Neurais/metabolismo , Neurotransmissores/farmacologia , Nicotina/farmacologia , Transtornos Relacionados ao Uso de Substâncias/metabolismoRESUMO
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 ß-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 ß-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.
Assuntos
Astrócitos/metabolismo , Hipocampo/metabolismo , Sistema de Sinalização das MAP Quinases/fisiologia , Morfina/farmacologia , Células-Tronco Neurais/metabolismo , Proteína Quinase C-épsilon/metabolismo , Proteínas de Ligação a RNA/metabolismo , Animais , Astrócitos/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células-Tronco Neurais/efeitos dos fármacos , Fosforilação/efeitos dos fármacosRESUMO
Oxycodone has been used clinically for over 90 years. While it is known that it exhibits low affinity for the multiple opioid receptors, whether its pharmacological activities are due to oxycodone activation of the opioid receptor type or due to its active metabolite (oxymorphone) that exhibits high affinity for the mu-opioid receptors remains unresolved. Ross and Smith (1997) reported the antinociceptive effects of oxycodone (171nmol, i.c.v.) are induced by putative kappa-opioid receptors in SD rat while others have reported oxycodone activities are due to activation of mu- and/or delta-opioid receptors. In this study, using male mu-opioid receptor knock-out (MOR-KO) mice, we examined whether delta-opioid receptor was involved in oxycodone antinociception. Systemic subcutaneous (s.c.) administration of oxycodone (above 40mg/kg) could induce a small but significant antinociceptive effect in MOR-KO mice by the tail flick test. Delta-opioid receptor antagonist (naltrindole, 10mg/kg or 20mg/kg, i.p.) could block this effect. When oxycodone was injected directly into the brain of MOR-KO mice by intracerebroventricular (i.c.v.) route, oxycodone at doses of 50nmol or higher could induce similar level of antinociceptive responses to those observed in wild type mice at the same doses by i.c.v. Delta-opioid receptor antagonists (naltrindole at 10nmol or ICI 154,129 at 20µg) completely blocked the supraspinal antinociceptive effect of oxycodone in MOR-KO mice. Such oxycodone antinociceptive responses were probably not due to its active metabolites oxymorphone because (a) the relative low level of oxymorphone was found in the brain after systemically or centrally oxycodone injection using LC/MS/MS analysis; (b) oxymorphone at a dose that mimics the level detected in the mice brain did not show any significant antinocieption effect; (c) oxycodone exhibits equal potency as oxymorphone albeit being a partial agonist in regulating [Ca(2+)]I transients in a clonal cell line expressing high level of mu-opioid receptor. These data suggest that oxycodone by itself can activate both the mu- and delta-opioid receptors and that delta-opioid receptors may contribute to the central antinociceptive effect of oxycodone in mice.
Assuntos
Analgésicos Opioides/farmacologia , Encéfalo/efeitos dos fármacos , Nociceptividade/efeitos dos fármacos , Dor Nociceptiva/prevenção & controle , Oxicodona/farmacologia , Limiar da Dor/efeitos dos fármacos , Receptores Opioides delta/agonistas , Analgésicos Opioides/administração & dosagem , Animais , Encéfalo/metabolismo , Encéfalo/fisiopatologia , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Genótipo , Injeções Intraventriculares , Injeções Subcutâneas , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Antagonistas de Entorpecentes/farmacologia , Dor Nociceptiva/genética , Dor Nociceptiva/metabolismo , Dor Nociceptiva/fisiopatologia , Oxicodona/administração & dosagem , Fenótipo , Receptores Opioides delta/metabolismo , Receptores Opioides mu/genética , Receptores Opioides mu/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fatores de TempoRESUMO
BACKGROUND: Pain management has been considered as significant contributor to broad quality-of-life improvement for cancer patients. Modulating serum cholesterol levels affects analgesia abilities of opioids, important pain killer for cancer patients, in mice system. Thus the correlation between opioids usages and cholesterol levels were investigated in human patients with lung cancer. METHODS: Medical records of 282 patients were selected with following criteria, 1) signed inform consent, 2) full medical records on total serum cholesterol levels and opioid administration, 3) opioid-naïve, 4) not received/receiving cancer-related or cholesterol lowering treatment, 5) pain level at level 5-8. The patients were divided into different groups basing on their gender and cholesterol levels. Since different opioids, morphine, oxycodone, and fentanyl, were all administrated at fixed low dose initially and increased gradually only if pain was not controlled, the percentages of patients in each group who did not respond to the initial doses of opioids and required higher doses for pain management were determined and compared. RESULTS: Patients with relative low cholesterol levels have larger percentage (11 out of 28 in female and 31 out of 71 in male) to not respond to the initial dose of opioids than those with high cholesterol levels (0 out of 258 in female and 8 out of 74 in male). Similar differences were obtained when patients with different opioids were analyzed separately. After converting the doses of different opioids to equivalent doses of oxycodone, significant correlation between opioid usages and cholesterol levels was also observed. CONCLUSIONS: Therefore, more attention should be taken to those cancer patients with low cholesterol levels because they may require higher doses of opioids as pain killer.
Assuntos
Analgésicos Opioides/administração & dosagem , Analgésicos Opioides/uso terapêutico , Colesterol/sangue , Neoplasias Pulmonares/sangue , Neoplasias Pulmonares/tratamento farmacológico , Manejo da Dor/métodos , Feminino , Fentanila/administração & dosagem , Fentanila/uso terapêutico , Humanos , Masculino , Morfina/administração & dosagem , Morfina/uso terapêutico , Oxicodona/administração & dosagem , Oxicodona/uso terapêuticoRESUMO
Heterogeneous nuclear ribonucleoprotein K (hnRNP K) binds to the promoter region of mu-opioid receptor (MOR) to regulate its transcriptional activity. How hnRNP K contributes to the analgesic effects of morphine, however, is largely unknown. We provide evidence that morphine increases hnRNP K protein expression via MOR activation in rat primary cortical neurons and HEK-293 cells expressing MORs, without increasing mRNA levels. Using the bicistronic reporter assay, we examined whether morphine-mediated accumulation of hnRNP K resulted from translational control. We identified potential internal ribosome entry site elements located in the 5' untranslated regions of hnRNP K transcripts that were regulated by morphine. This finding suggests that internal translation contributes to the morphine-induced accumulation of hnRNP K protein in regions of the central nervous system correlated with nociceptive and antinociceptive modulatory systems in mice. Finally, we found that down-regulation of hnRNP K mediated by siRNA attenuated morphine-induced hyperpolarization of membrane potential in AtT20 cells. Silencing hnRNP K expression in the spinal cord increased nociceptive sensitivity in wild-type mice, but not in MOR-knockout mice. Thus, our findings identify the role of translational control of hnRNP K in morphine-induced analgesia through activation of MOR.
Assuntos
Regiões 5' não Traduzidas/efeitos dos fármacos , Analgésicos Opioides/farmacologia , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/biossíntese , Morfina/farmacologia , Neurônios/metabolismo , Biossíntese de Proteínas/efeitos dos fármacos , Receptores Opioides mu/metabolismo , Animais , Sequência de Bases , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Células Cultivadas , Sequência Conservada , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/metabolismo , Células HEK293 , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Humanos , Camundongos , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Neurônios/efeitos dos fármacos , Nociceptividade , Ratos , Ribossomos/metabolismo , Transdução de Sinais , Medula Espinal/efeitos dos fármacos , Medula Espinal/metabolismo , Regulação para CimaRESUMO
During the past decade, the study of the mechanisms and functional implications of adult neurogenesis has significantly progressed. Many studies focus on the factors that regulate proliferation and fate determination of adult neural stem/progenitor cells, including addictive drugs such as opioid. Here, we review the most recent works on opiate drugs' effect on different developmental stages of adult hippocampal neurogenesis, as well as the possible underlying mechanisms. We conclude that opiate drugs in general cause a loss of newly born neural progenitors in the subgranular zone of dentate gyrus, by either modulating proliferation or interfering with differentiation and maturation. We also discuss the consequent impact of regulation of adult neurogenesis in animal's opioid addiction behavior. We further look into the future directions in studying the convergence between the adult neurogenesis field and opioid addiction field, since the adult-born granular cells were shown to play a role in neuroplasticity and may help to reduce the vulnerability to drug craving and relapse.
Assuntos
Envelhecimento/fisiologia , Analgésicos Opioides/farmacologia , Hipocampo/fisiologia , Neurogênese/efeitos dos fármacos , Animais , Apoptose/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Humanos , Células-Tronco Neurais/citologia , Células-Tronco Neurais/efeitos dos fármacosRESUMO
The mechanism by which addictive drugs such as morphine regulate adult neurogenesis remains elusive. We now demonstrate that morphine can regulate neurogenesis by control of miR-181a and subsequent hippocampal neural progenitor cell (hNPC) lineages. In the presence of morphine, hNPCs preferentially differentiated into astrocytes, an effect blocked by the specific µ-opioid receptor antagonist, Cys(2)-Tyr(3)-Orn(5)-Pen(7)-amide. This effect was mediated by the Prox1/Notch1 pathway as demonstrated by an increase in Notch1 level in the morphine- but not fentanyl-treated hNPCs and blocked by overexpression of Notch1 siRNA. Overexpression of Prox1 siRNA upregulated Notch1 level and potentiated the morphine-induced lineage changes. Prox1 transcript level was regulated by direct interaction between miR-181a and its 3'-UTR sequence. In vitro and in vivo treatment with morphine resulted in an increase in miR-181a level in hNPCs and mouse hippocampi, respectively. Overexpression of miR-181a mimics reduced Prox1 levels, increased Notch1 levels, and enhanced hNPCs differentiation into astrocytes. Meanwhile, overexpression of the miR-181a inhibitor raised Prox1 levels, decreased Notch1 levels, and subsequently blocked the morphine-induced lineage changes. Thus, by modulating Prox1/Notch1 activities via miR-181a, morphine influences the fate of differentiating hNPCs differentiation and therefore the ultimate quantities of mature neurons and astrocytes.