RESUMO
Opioids are effective analgesics, but their use is beset by serious side effects, including addiction and respiratory depression, which contribute to the ongoing opioid crisis. The human opioid system contains four opioid receptors (µOR, δOR, κOR, and NOPR) and a set of related endogenous opioid peptides (EOPs), which show distinct selectivity toward their respective opioid receptors (ORs). Despite being key to the development of safer analgesics, the mechanisms of molecular recognition and selectivity of EOPs to ORs remain unclear. Here, we systematically characterize the binding of EOPs to ORs and present five structures of EOP-OR-Gi complexes, including ß-endorphin- and endomorphin-bound µOR, deltorphin-bound δOR, dynorphin-bound κOR, and nociceptin-bound NOPR. These structures, supported by biochemical results, uncover the specific recognition and selectivity of opioid peptides and the conserved mechanism of opioid receptor activation. These results provide a structural framework to facilitate rational design of safer opioid drugs for pain relief.
Assuntos
Receptores Opioides , Humanos , Analgésicos Opioides/farmacologia , Peptídeos Opioides , Receptores Opioides mu/metabolismo , Receptores Opioides/químicaRESUMO
Alcohol use disorder is complex and multifaceted, involving the coordination of multiple signaling systems across numerous brain regions. Previous work has indicated that both the insular cortex and dynorphin (DYN)/kappa opioid receptor (KOR) systems contribute to excessive alcohol use. More recently, we identified a microcircuit in the medial aspect of the insular cortex that signals through DYN/KOR. Here, we explored the role of insula DYN/KOR circuit components on alcohol intake in a long-term intermittent access (IA) procedure. Using a combination of conditional knock-out strategies and site-directed pharmacology, we discovered distinct and sex-specific roles for insula DYN and KOR in alcohol drinking and related behavior. Our findings show that insula DYN deletion blocked escalated consumption and decreased the overall intake of and preference for alcohol in male and female mice. This effect was specific to alcohol in male mice, as DYN deletion did not impact sucrose intake. Further, insula KOR antagonism reduced alcohol intake and preference during the early phase of IA in male mice only. Alcohol consumption was not affected by insula KOR knockout in either sex. In addition, we found that long-term IA decreased the intrinsic excitability of DYN and deep layer pyramidal neurons (DLPNs) in the insula of male mice. Excitatory synaptic transmission was also impacted by IA, as it drove an increase in excitatory synaptic drive in both DYN neurons and DLPNs. Combined, our findings suggest there is a dynamic interplay between excessive alcohol consumption and insula DYN/KOR microcircuitry.SIGNIFICANCE STATEMENT The insular cortex is a complex region that serves as an integratory hub for sensory inputs. In our previous work, we identified a microcircuit in the insula that signals through the kappa opioid receptor (KOR) and its endogenous ligand dynorphin (DYN). Both the insula and DYN/KOR systems have been implicated in excessive alcohol use and alcohol use disorder (AUD). Here, we use converging approaches to determine how insula DYN/KOR microcircuit components contribute to escalated alcohol consumption. Our findings show that insula DYN/KOR systems regulate distinct phases of alcohol consumption in a sex-specific manner, which may contribute to the progression to AUD.
Assuntos
Alcoolismo , Receptores Opioides kappa , Feminino , Camundongos , Masculino , Animais , Receptores Opioides kappa/metabolismo , Dinorfinas/metabolismo , Córtex Insular , Consumo de Bebidas Alcoólicas , EtanolRESUMO
This study aimed to elucidate the opioid mechanisms underlying dexamethasone-induced pain antihypersensitive effects in neuropathic rats. Dexamethasone (subcutaneous and intrathecal) and membrane-impermeable Dex-BSA (intrathecal) administration dose-dependently inhibited mechanical allodynia and thermal hyperalgesia in neuropathic rats. Dexamethasone and Dex-BSA treatments increased expression of dynorphin A in the spinal cords and primary cultured microglia. Dexamethasone specifically enhanced dynorphin A expression in microglia but not astrocytes or neurons. Intrathecal injection of the microglial metabolic inhibitor minocycline blocked dexamethasone-stimulated spinal dynorphin A expression; intrathecal minocycline, the glucocorticoid receptor antagonist Dex-21-mesylate, dynorphin A antiserum, and κ-opioid receptor antagonist GNTI completely blocked dexamethasone-induced mechanical antiallodynia and thermal antihyperalgesia. Additionally, dexamethasone elevated spinal intracellular cAMP levels, leading to enhanced phosphorylation of PKA, p38 MAPK and CREB. The specific adenylate cyclase inhibitor DDA, PKA inhibitor H89, p38 MAPK inhibitor SB203580 and CREB inhibitor KG-501 completely blocked dexamethasone-induced anti-neuropathic pain and increased microglial dynorphin A exprression. In conclusion, this study reveal that dexamethasone mitigateds neuropathic pain through upregulation of dynorphin A in spinal microglia, likely involving the membrane glucocorticoid receptor/cAMP/PKA/p38 MAPK/CREB signaling pathway.
Assuntos
Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico , Proteínas Quinases Dependentes de AMP Cíclico , AMP Cíclico , Dexametasona , Dinorfinas , Microglia , Neuralgia , Ratos Sprague-Dawley , Transdução de Sinais , Medula Espinal , Proteínas Quinases p38 Ativadas por Mitógeno , Animais , Microglia/metabolismo , Microglia/efeitos dos fármacos , AMP Cíclico/metabolismo , Medula Espinal/metabolismo , Medula Espinal/efeitos dos fármacos , Masculino , Neuralgia/metabolismo , Neuralgia/tratamento farmacológico , Dinorfinas/metabolismo , Ratos , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Dexametasona/farmacologia , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Transdução de Sinais/efeitos dos fármacos , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Hiperalgesia/metabolismo , Hiperalgesia/tratamento farmacológicoRESUMO
The dynorphin peptides are the endogenous ligands for the kappa opioid receptor (KOR) and regulate food intake. Administration of dynorphin-A1-13 (DYN) in the paraventricular hypothalamic nucleus (PVN) increases palatable food intake, and this effect is blocked by co-administration of the orexin-A neuropeptide, which is co-released with DYN in PVN from neurons located in the lateral hypothalamus. While PVN administration of DYN increases palatable food intake, whether it increases food-seeking behaviors has yet to be examined. We tested the effects of DYN and norBNI (a KOR antagonist) on the seeking and consumption of sucrose using a progressive ratio (PR) and demand curve (DC) tasks. In PVN, DYN did not alter the sucrose breaking point (BP) in the PR task nor the elasticity or intensity of demand for sucrose in the DC task. Still, DYN reduced the delay in obtaining sucrose and increased licks during sucrose intake in the PR task, irrespective of the co-administration of orexin-A. In PVN, norBNI increased the delay in obtaining sucrose and reduced licks during sucrose intake in the PR task while increasing elasticity without altering intensity of demand in the DC task. However, subcutaneous norBNI reduced the BP for sucrose and increased the delay in obtaining sucrose in the PR task while reducing the elasticity of demand. Together, these data show different effects of systemic and PVN blockade of KOR on food-seeking, consummatory behaviors, and incentive motivation for sucrose and suggest that KOR activity in PVN is necessary but not sufficient to drive seeking behaviors for palatable food.
Assuntos
Dinorfinas , Motivação , Núcleo Hipotalâmico Paraventricular , Receptores Opioides kappa , Receptores Opioides kappa/metabolismo , Dinorfinas/farmacologia , Dinorfinas/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Animais , Masculino , Motivação/efeitos dos fármacos , Orexinas , Ratos , Ratos Sprague-Dawley , Naltrexona/farmacologia , Naltrexona/análogos & derivados , Ingestão de Alimentos/efeitos dos fármacos , Ingestão de Alimentos/fisiologia , Ingestão de Alimentos/psicologia , Sacarose , Comportamento Alimentar/efeitos dos fármacos , Comportamento Alimentar/psicologia , Antagonistas de Entorpecentes/farmacologiaRESUMO
Kappa opioid receptor (KOR) antagonists have potential therapeutic applications in the treatment of stress-induced relapse to substance abuse and mood disorders. The dynorphin A analog arodyn (Ac[Phe1,2,3,Arg4,D-Ala8]dynorphin A-(1-11)-NH2) exhibits potent and selective kappa opioid receptor antagonism. Multiple cyclizations in longer peptides, such as dynorphin and its analogs, can extend the conformational constraint to additional regions of the peptide beyond what is typically constrained by a single cyclization. Here, we report the design, synthesis, and pharmacological evaluation of a bicyclic arodyn analog with two constraints in the opioid peptide sequence. The peptide, designed based on structure-activity relationships of monocyclic arodyn analogs, was synthesized by solid-phase peptide synthesis and cyclized by sequential ring-closing metathesis (RCM) in the C- and N-terminal sequences. Molecular modeling studies suggest similar interactions of key aromatic and basic residues in the bicyclic peptide with KOR as found in the cryoEM structure of KOR-bound dynorphin, despite substantial differences in the backbone conformations of the two peptides. The bicyclic peptide's affinities at KOR and mu opioid receptors (MOR) were determined in radioligand binding assays, and its KOR antagonism was determined in the [35S]GTPγS assay in KOR-expressing cells. The bicyclic analog retains KOR affinity and selectivity (Ki = 26 nM, 97-fold selectivity over MOR) similar to arodyn and exhibits potent KOR antagonism in the dynorphin-stimulated [35S]GTPγS assay. This bicyclic peptide represents a promising advance in preparing cyclic opioid peptide ligands and opens avenues for the rational design of additional bicyclic opioid peptide analogs.
Assuntos
Dinorfinas , Receptores Opioides kappa , Receptores Opioides kappa/antagonistas & inibidores , Receptores Opioides kappa/metabolismo , Dinorfinas/química , Dinorfinas/farmacologia , Humanos , Animais , Relação Estrutura-Atividade , Modelos Moleculares , Peptídeos Cíclicos/química , Peptídeos Cíclicos/farmacologia , Peptídeos Cíclicos/síntese química , Sequência de AminoácidosRESUMO
Ion channels of the degenerin (DEG)/epithelial Na+ channel (ENaC) family serve diverse functions ranging from mechanosensation over Na+ reabsorption to H+ sensing and neurotransmission. However, several diverse DEG/ENaCs interact with neuropeptides; some are directly activated, whereas others are modulated by neuropeptides. Two questions arise: does this interaction have a common structural basis and does it have an ancient origin? Current evidence suggests that RFamide neuropeptides activate the FMRFamide-activated Na+ channels (FaNaCs) of invertebrates via binding to a pocket at the external face of their large extracellular domain. It is likely that RFamides might activate DEG/ENaCs from the freshwater polyp Hydra (the HyNaCs) via binding to a similar pocket, although there is not yet any experimental evidence. In contrast, RFamide neuropeptides modulate acid-sensing ion channels (ASICs) from vertebrates via binding to a central cavity enclosed by ß-sheets of the extracellular domain. Dynorphin opioid peptides, for their part, bind to the acidic pocket of ASICs, which might be evolutionarily related to the peptide binding pocket of FaNaCs, but instead of opening the channels they work as antagonists to stabilize its closed state. Moreover, peptides interacting with DEG/ENaCs from animals of different phyla, although having similar sequences, are evolutionarily unrelated to each other. Collectively, it appears that despite a seemingly similar interaction with similar peptides, the interaction of DEG/ENaCs with neuropeptides has diverse structural bases and many origins.
Assuntos
Cnidários , Neuropeptídeos , Animais , Canais de Sódio Degenerina/metabolismo , Cnidários/metabolismo , Neuropeptídeos/metabolismo , Peptídeos , Canais Iônicos Sensíveis a Ácido/metabolismo , Íons/metabolismo , Mamíferos/metabolismo , Canais Epiteliais de Sódio/metabolismoRESUMO
Dynorphin A (1-17) (DynA17) has been identified as a key regulator of both sensory and affective dimensions of chronic pain. Following nerve injury, increases in DynA17 have been reported in the spinal and supraspinal areas involved in chronic pain. Blocking these increases provides therapeutic benefits in preclinical chronic pain models. Although heavily characterized at the behavioral level, how DynA17 mediates its effects at the cellular physiological level has not been investigated. In this report, we begin to decipher how DynA17 mediates its direct effects on mouse dorsal root ganglion (DRG) cells and how intrathecal administration modifies a key node in the pain axis, the periaqueductal gray These findings build on the plethora of literature defining DynA17 as a critical neuropeptide in the pathophysiology of chronic pain syndromes.
Assuntos
Dor Crônica , Neuropeptídeos , Camundongos , Animais , Dinorfinas , Gânglios EspinaisRESUMO
Accumulating findings during the past decades have demonstrated that the hypothalamic arcuate kisspeptin neurons are supposed to be responsible for pulsatile release of gonadotropin-releasing hormone (GnRH) to regulate gametogenesis and steroidogenesis in mammals. The arcuate kisspeptin neurons express neurokinin B (NKB) and dynorphin A (Dyn), thus, the neurons are also referred to as KNDy neurons. In the present article, we mainly focus on the cellular and molecular mechanisms underlying GnRH pulse generation, that is focused on the action of NKB and Dyn and an interaction between KNDy neurons and astrocytes to control GnRH pulse generation. Then, we also discuss the factors that modulate the activity of KNDy neurons and consequent pulsatile GnRH/LH release in mammals.
Assuntos
Núcleo Arqueado do Hipotálamo , Hormônio Liberador de Gonadotropina , Animais , Núcleo Arqueado do Hipotálamo/metabolismo , Dinorfinas/metabolismo , Hormônio Liberador de Gonadotropina/metabolismo , Kisspeptinas/metabolismo , Mamíferos , Neurocinina B/metabolismo , Neurônios/metabolismoRESUMO
Alcohol use is a major cause of disability and death globally. These negative consequences disproportionately affect people who develop alcohol addiction, a chronic relapsing condition characterized by increased motivation to use alcohol, choice of alcohol over healthy, natural rewards, and continued use despite negative consequences. Available pharmacotherapies for alcohol addiction are few, have effect sizes in need of improvement, and remain infrequently prescribed. Research aimed at developing novel therapeutics has in large part focused on attenuating pleasurable or "rewarding" properties of alcohol, but this targets processes that primarily play a role as initiation factors. As clinical alcohol addiction develops, long-term changes in brain function result in a shift of affective homeostasis, and rewarding alcohol effects become progressively reduced. Instead, increased stress sensitivity and negative affective states emerge in the absence of alcohol and create powerful incentives for relapse and continued use through negative reinforcement, or "relief." Based on research in animal models, several neuropeptide systems have been proposed to play an important role in this shift, suggesting that these systems could be targeted by novel medications. Two mechanisms in this category, antagonism at corticotropin-releasing factor type 1, and neurokinin 1/substance P receptors, have been subject to initial evaluation in humans. A third, kappa-opioid receptor antagonism, has been evaluated in nicotine addiction and could soon be tested for alcohol. This paper discusses findings with these mechanisms to date, and their prospects as future targets for novel medications.
Assuntos
Alcoolismo , Neuropeptídeos , Animais , Humanos , Alcoolismo/tratamento farmacológico , Alcoolismo/psicologia , Neuropeptídeos/metabolismo , Encéfalo/metabolismo , Hormônio Liberador da Corticotropina/metabolismo , Consumo de Bebidas Alcoólicas , EtanolRESUMO
Self-injurious behavior (SIB) can lead to serious injury and occurs in approximately 1%-4% of the adult population, with higher incidences in adolescent and institutionalized populations, as well as in children with developmental disorders such as Autism. SIB also spontaneously occurs in a low percentage of captive monkeys. Rhesus macaque (Macaca mulatta) monkeys are evolutionarily and physiologically similar to humans, share 93% genetic sequence similarity to humans, and have long been used as testing subjects for vaccine and clinical trials. Previous studies hypothesized that altered endogenous opioid expression occurs in the brains of individuals and animals that self-injure. We examined the regional mRNA expression of opioid signaling genes in sixteen rhesus macaques that exhibited SIB and eight sex- and age- matched controls. The brain regions examined are linked to reward reinforcement and stress adaptation including the hypothalamus, orbital frontal cortex, nucleus accumbens, hippocampus, caudate, and the amygdala. We found decreased µ-opioid receptor (OPRM1) in the amygdala of monkeys with SIB, and reduced prodynorphin (PDYN) in the hypothalamus. Our data suggest dysfunction in the regulation of opioid peptide precursors and calls for further investigation of the endogenous opioid system in SIB.
Assuntos
Analgésicos Opioides , Comportamento Autodestrutivo , Animais , Criança , Humanos , Adolescente , Macaca mulatta/metabolismo , Peptídeos Opioides , Comportamento Autodestrutivo/genética , Núcleo Accumbens/metabolismoRESUMO
Chronic exposure to methamphetamine (METH) causes severe and persistent cognitive impairment. The present study aimed to investigate the role of dynorphin/κ opioid receptor (KOR) system in the development of METH-induced cognitive impairment. We found that mice showed significant cognitive impairment in the novel object recognition test (NOR) following daily injections of METH (10 mg/kg) for seven consecutive days. Systemic blockade of KOR prevented METH-induced cognitive impairment by pretreatment of the selective KOR antagonist norBNI (10 mg/kg, i.p.) or KOR deletion. Then, significant increased dynorphin and KOR mRNA were observed exclusively in prelimbic cortex (PL) other than infralimbic cortex. Finally, microinjection with norBNI into PL also improved cognitive memory in METH-treated mice using NOR and spontaneous alternation behaviour test. Our results demonstrated that dynorphin/KOR system activation in PL may be a possible mechanism for METH-induced cognitive impairment and shed light on KOR antagonists as a potential neuroprotective agent against the cognitive deficits induced by drug abuse.
Assuntos
Transtornos Cognitivos , Disfunção Cognitiva , Metanfetamina , Animais , Camundongos , Dinorfinas , Receptores Opioides kappa , Disfunção Cognitiva/induzido quimicamente , Disfunção Cognitiva/prevenção & controle , Metanfetamina/farmacologia , Antagonistas de EntorpecentesRESUMO
BACKGROUND: To explore the relationships between anxiety/depression and NERD, we focused on dynorphin (Dyn), an important member of visceral hypersensitivity, and its related pathways. METHODS: Pearson's correlation analysis on patients with NERD and in vivo experiment on NERD rat model. Part 1: Pearson's correlation analysis among serum levels of Dyn, clinical symptoms and HADS scores of NERD patients were carried on. Part 2: Wistar rats were randomly divided into 2 groups: control group and model group. The data of pH value, immobility time, serum Dyn concentration, NMDAR1 and SP expression were, respectively, derived from automatic pH recorder, tail suspension test, enzyme-linked immunosorbent assay, immunohistochemistry and immunofluorescence. RESULTS: Part 1: Pearson's correlation analysis showed that there was a linear correlation between Clinical Symptom (CS) score and HADS score (HAD-A, HAD-D), and the correlation coefficients were 0.385 and 0.273 respectively; the correlation coefficient between lg (Dyn) and lg (CS score) was r = 0.441, P = 0.002; the correlation coefficient between lg(Dyn) and lg (HAD-D score) was r = 0.447, P = 0.002. Part 2: The pH value of the lower esophagus in the model group was lower than that in the control group (P < 0.01). The tail suspension immobility time of model group was significantly longer than that of control group (P < 0.01). The serum Dyn concentration and the expression level of NMDAR1 in spinal cord and SP in lower esophageal mucosa of model group were significantly higher than those of control group (P < 0.05). CONCLUSION: Increased serum dynorphin level may be a sign of correlation between depression and NERD.
Assuntos
Depressão , Dinorfinas , Refluxo Gastroesofágico , Animais , Ratos , Depressão/complicações , Depressão/metabolismo , Dinorfinas/metabolismo , Refluxo Gastroesofágico/metabolismo , Ratos WistarRESUMO
BACKGROUND: Adverse pathophysiological and behavioral outcomes related to mild traumatic brain injury (mTBI), posttraumatic stress disorder (PTSD), and chronic pain are common following blast exposure and contribute to decreased quality of life, but underlying mechanisms and prophylactic/treatment options remain limited. The dynorphin/kappa opioid receptor (KOR) system helps regulate behavioral and inflammatory responses to stress and injury; however, it has yet to be investigated as a potential mechanism in either humans or animals exposed to blast. We hypothesized that blast-induced KOR activation mediates adverse outcomes related to inflammation and affective behavioral response. METHODS: C57Bl/6 adult male mice were singly or repeatedly exposed to either sham (anesthesia only) or blast delivered by a pneumatic shock tube. The selective KOR antagonist norBNI or vehicle (saline) was administered 72 h prior to repetitive blast or sham exposure. Serum and brain were collected 10 min or 4 h post-exposure for dynorphin A-like immunoreactivity and cytokine measurements, respectively. At 1-month post-exposure, mice were tested in a series of behavioral assays related to adverse outcomes reported by humans with blast trauma. RESULTS: Repetitive but not single blast exposure resulted in increased brain dynorphin A-like immunoreactivity. norBNI pretreatment blocked or significantly reduced blast-induced increase in serum and brain cytokines, including IL-6, at 4 h post exposure and aversive/anxiety-like behavioral dysfunction at 1-month post-exposure. CONCLUSIONS: Our findings demonstrate a previously unreported role for the dynorphin/KOR system as a mediator of biochemical and behavioral dysfunction following repetitive blast exposure and highlight this system as a potential prophylactic/therapeutic treatment target.
Assuntos
Traumatismos por Explosões , Dinorfinas , Receptores Opioides kappa , Animais , Masculino , Camundongos , Traumatismos por Explosões/complicações , Traumatismos por Explosões/genética , Traumatismos por Explosões/imunologia , Encéfalo/imunologia , Encéfalo/fisiologia , Dinorfinas/genética , Dinorfinas/imunologia , Qualidade de Vida , Receptores Opioides kappa/genética , Receptores Opioides kappa/imunologiaRESUMO
Latest studies have revealed that pain negatively impacts on reward processing and motivation leading to negative affective states and stress. These states not only reduce quality of life of patients by increasing the appearance of psychiatric comorbidities, but also have an important impact on vulnerability to drug abuse, including alcohol. In fact, clinical, epidemiological but also preclinical studies have revealed that the presence of pain is closely related to alcohol use disorders (AUDs). All this evidence suggests that pain is a factor that increases the risk of suffering AUD, predicting heavy drinking behavior and relapse drinking in those patients with a previous history of AUD. The negative consequences of chronic pain and its impact on stress and AUD are likely mediated by alterations in the central nervous system, especially in the stress and reward systems. Therefore, pain and stress impact on dopaminergic mesolimbic pathway can lead to an increase in drug abuse liability. In this mini review we analyze the interaction between pain, stress, and alcohol addiction, and how dynamic changes in the kappa opioid system might play a crucial role in the development of compulsive alcohol drinking in chronic pain patients.
Assuntos
Alcoolismo , Dor Crônica , Alcoolismo/complicações , Dor Crônica/psicologia , Dopamina/metabolismo , Humanos , Qualidade de Vida , RecompensaRESUMO
In previous studies, we found that dynorphin exerts antiepileptic effect by activating the kappa opioid receptor (KOR). However, the role of neuronal autophagy in dynorphin/KOR-mediated antiepileptic is still unclear. This study aimed to investigate the molecular mechanism of dynorphin's antiepileptic effect by inhibiting autophagy and reducing neuronal apoptosis. Here, a pilocarpine-induced rat model of epilepsy was established and hippocampal neurons were treated with Mg2+ -free exposed for epileptiform activity induction. The real-time polymerase chain reaction and Western blot analysis were used to evaluate messenger RNA and protein expression. The TdT-mediated dUTP-biotin nick end labeling staining and flow cytometry were used to analyze cell apoptosis in vivo and in vitro. Neuron cells viability was detected by Cell Counting Kit-8 assay. Immunofluorescent staining and green fluorescent protein-light chain 3 immunofluorescence were used to measure autophagy in vivo and in vitro. Results showed that overexpression of prodynorphin alleviated neuronal apoptosis, activated the mammalian target of rapamycin (mTOR) signaling pathway, and inhibited neuronal autophagy in epileptic rats. Dynorphin inhibited Mg2+ -free-induced seizure-like neuron apoptosis, partially reversing the effect of Mg2+ -free on the mTOR signaling pathway and seizure-like neuron autophagy. Further, using rapamycin, we found that dynorphin inhibited Mg2+ -free-induced seizure-like neuron autophagy and apoptosis by activating the mTOR signaling pathway. In conclusion, dynorphin inhibits autophagy by activating the mTOR signaling pathway and has a protective effect on epilepsy acute seizure and epilepsy-induced brain injury.
Assuntos
Dinorfinas , Epilepsia , Animais , Anticonvulsivantes/farmacologia , Apoptose , Autofagia , Biotina/metabolismo , Biotina/farmacologia , Biotina/uso terapêutico , Epilepsia/induzido quimicamente , Epilepsia/metabolismo , Proteínas de Fluorescência Verde , Mamíferos/metabolismo , Pilocarpina , RNA Mensageiro , Ratos , Ratos Sprague-Dawley , Receptores Opioides kappa/uso terapêutico , Convulsões/induzido quimicamente , Transdução de Sinais , Sirolimo/farmacologia , Serina-Treonina Quinases TOR/metabolismoRESUMO
Major depression disorder is a severe and recurrent neuropsychological disorder characterized by lowered mood and social activity and cognitive impairment. Owing to unclear molecular mechanisms of depression, limited interventions are available in clinic. In this study we investigated the role of dynorphin/κ opioid receptor system in the development of depression. Mice were subjected to chronic social defeat stress for 14 days. Chronic social defeat stress induced significant social avoidance in mice characterized by decreased time duration in the interaction zone and increased time duration in the corner zone. Pre-administration of a κ opioid receptor antagonist norBNI (10 mg/kg, i.p.) could prevent the development of social avoidance induced by chronic social defeat stress. Social avoidance was not observed in κ opioid receptor knockout mice subjected to chronic social defeat stress. We further revealed that social defeat stress activated c-fos and ERK signaling in the amygdala without affecting the NAc, hippocampus and hypothalamus, and ERK activation was blocked by systemic injection of norBNI. Finally, the expression of dynorphin A, the endogenous ligand of κ opioid receptor, was significantly increased in the amygdala following social defeat stress; microinjection of norBNI into the amygdala prevented the development of depressive-like behaviors caused by social defeat stress. The present study demonstrates that upregulated dynorphin/κ opioid receptor system in the amygdala leads to the emergence of depression following chronic social defeat stress, and sheds light on κ opioid receptor antagonists as potential therapeutic agents for the prevention and treatment of depression following chronic stress.
Assuntos
Tonsila do Cerebelo/metabolismo , Transtorno Depressivo Maior/patologia , Dinorfinas/metabolismo , Receptores Opioides kappa/antagonistas & inibidores , Comportamento Social , Derrota Social , Animais , Comportamento Animal , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Naltrexona/análogos & derivados , Naltrexona/farmacologia , Proteínas Proto-Oncogênicas c-fos/metabolismoRESUMO
The orexin peptides promote hedonic intake and other reward behaviors through different brain sites. The opioid dynorphin peptides are co-released with orexin peptides but block their effects on reward in the ventral tegmental area (VTA). We previously showed that in the paraventricular hypothalamic nucleus (PVN), dynorphin and not orexin peptides enhance hedonic intake, suggesting they have brain-site-specific effects. Obesity alters the expression of orexin and dynorphin receptors, but whether their expression across different brain sites is important to hedonic intake is unclear. We hypothesized that hedonic intake is regulated by orexin and dynorphin peptides in PVN and that hedonic intake in obesity correlates with expression of their receptors. Here we show that in mice, injection of DYN-A1-13 (an opioid dynorphin peptide) in the PVN enhanced hedonic intake, whereas in the VTA, injection of OXA (orexin-A, an orexin peptide) enhanced hedonic intake. In PVN, OXA blunted the increase in hedonic intake caused by DYN-A1-13. In PVN, injection of norBNI (opioid receptor antagonist) reduced hedonic intake but a subsequent OXA injection failed to increase hedonic intake, suggesting that OXA activity in PVN is not influenced by endogenous opioid activity. In the PVN, DYN-A1-13 increased the intake of the less-preferred food in a two-food choice task. In obese mice fed a cafeteria diet, orexin 1 receptor mRNA across brain sites involved in hedonic intake correlated with fat preference but not caloric intake. Together, these data support that orexin and dynorphin peptides regulate hedonic intake in an opposing manner with brain-site-specific effects.
Assuntos
Dinorfinas , Núcleo Hipotalâmico Paraventricular , Analgésicos Opioides/metabolismo , Analgésicos Opioides/farmacologia , Animais , Encéfalo/metabolismo , Dinorfinas/metabolismo , Dinorfinas/farmacologia , Camundongos , Obesidade/metabolismo , Orexinas/metabolismoRESUMO
Kisspeptin (KISS), a key hormone involved in the regulation of the hypothalamic-pituitary-ovarian (HPO) axis, has been localized in the anteroventral periventricular (AVPV) nucleus and the neighboring rostral periventricular nucleus (PeVN), and in the arcuate (ARC) nucleus of the mammalian hypothalamus. In the ARC, the KISS neurons that co-express neurokinin B (NKB) and dynorphin A (Dyn) are named KNDy cells. The South American plains vizcacha is a rodent with peculiar reproductive traits. Around mid-pregnancy, vizcacha shows the reactivation of its HPO axis with the pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH), an essential event for the success of gestation. Considering the role of KISS system in GnRH modulation, the aim of this work was to study their neuroanatomical distribution in adult vizcachas. AVPV showed sexual dimorphism with a significant smaller area in males (t-Test, p < 0.05), and KISS immunoreactivity was detected in somas and varicosities homogenously distributed in the AVPV with a concordant sex-related expression pattern. NKB and Dyn expression was also observed in cytoplasm of neurons scattered in the AVPV. Three subpopulations of neurons were detected in the AVPV: neurons expressing Dyn and NKB (DyNK cells), neurons expressing KISS and NKB (KiNK cells), and single NKB expressing neurons. Strikingly, KISS and Dyn were always expressed in different cells. In addition, in the ARC nucleus, KNDy cells were detected. On the other hand, KISS and GnRH expression was detected in different subpopulations of neurons, GnRH cells showed KISS receptor (KISSR or GPR-54) expression, and KISS immunoreactive afferent contacts were detected making close appositions onto somas and dendrites of GnRH cells. These results show similarities and differences between the KISS system in the hypothalamus of the vizcacha and other mammals, and constitute crucial observations about KISS and GnRH relation. Considering the peculiarity of HPO axis regulation in this species, the present work provides a neuroanatomical framework for the further elucidation of molecular mechanisms underlying GnRH expression and secretion.
Assuntos
Hormônio Liberador de Gonadotropina , Kisspeptinas , Animais , Núcleo Arqueado do Hipotálamo/metabolismo , Feminino , Hormônio Liberador de Gonadotropina/metabolismo , Hipotálamo/metabolismo , Kisspeptinas/metabolismo , Masculino , Mamíferos/metabolismo , Neurocinina B/metabolismo , Gravidez , América do SulRESUMO
Antibodies are important tools for protein and peptide research, including for the kappa opioid receptor (KOR) and dynorphins (Dyns). Well-characterized antibodies are essential for rigorous and reproducible research. However, lack of validation of antibody specificity has been thought to contribute significantly to the reproducibility crisis in biomedical research. Since 2003, many scientific journals have required documentation of validation of antibody specificity and use of knockout mouse tissues as a negative control is strongly recommended. Lack of specificity of antibodies against many G protein-coupled receptors (GPCRs) after extensive testing has been well-documented, but antibodies generated against partial sequences of the KOR have not been similarly investigated. For the dynorphins, differential processing has been described in distinct brain areas, resulting in controversial findings in immunohistochemistry (IHC) when different antibodies were used. In this chapter, we summarized accepted approaches for validation of antibody specificity. We discussed two KOR antibodies most commonly used in IHC and described generation and characterization of KOR antibodies and phospho-KOR specific antibodies in western blotting or immunoblotting (IB). In addition, applying antibodies targeting prodynorphin or mature dynorphin A illustrates the diversity of results obtained regarding the distribution of dynorphins in distinct brain areas.
Assuntos
Dinorfinas , Receptores Opioides kappa , Animais , Encéfalo/metabolismo , Camundongos , Camundongos Knockout , Reprodutibilidade dos TestesRESUMO
Cortical circuits control a plethora of behaviors, from sensation to cognition. The cortex is enriched with neuropeptides and receptors that play a role in information processing, including opioid peptides and their cognate receptors. The dynorphin (DYN)/kappa-opioid receptor (KOR) system has been implicated in the processing of sensory and motivationally-charged emotional information and is highly expressed in cortical circuits. This is important as dysregulation of DYN/KOR signaling in limbic and cortical circuits has been implicated in promoting negative affect and cognitive deficits in various neuropsychiatric disorders. However, research investigating the role of this system in controlling cortical circuits and computations therein is limited. Here, we review the (1) basic anatomy of cortical circuits, (2) anatomical architecture of the cortical DYN/KOR system, (3) functional regulation of cortical synaptic transmission and microcircuit function by the DYN/KOR system, (4) regulation of behavior by the cortical DYN/KOR system, (5) implications for the DYN/KOR system for human health and disease, and (6) future directions and unanswered questions for the field. Further work elucidating the role of the DYN/KOR system in controlling cortical information processing and associated behaviors will be of importance to increasing our understanding of principles underlying neuropeptide modulation of cortical circuits, mechanisms underlying sensation and perception, motivated and emotional behavior, and cognition. Increased emphasis in this area of study will also aid in the identification of novel ways to target the DYN/KOR system to treat neuropsychiatric disorders.