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1.
Nat Commun ; 12(1): 5249, 2021 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-34475397

RESUMO

The wake-active orexin system plays a central role in the dynamic regulation of glucose homeostasis. Here we show orexin receptor type 1 and 2 are predominantly expressed in dorsal raphe nucleus-dorsal and -ventral, respectively. Serotonergic neurons in ventral median raphe nucleus and raphe pallidus selectively express orexin receptor type 1. Inactivation of orexin receptor type 1 in serotonin transporter-expressing cells of mice reduced insulin sensitivity in diet-induced obesity, mainly by decreasing glucose utilization in brown adipose tissue and skeletal muscle. Selective inactivation of orexin receptor type 2 improved glucose tolerance and insulin sensitivity in obese mice, mainly through a decrease in hepatic gluconeogenesis. Optogenetic activation of orexin neurons in lateral hypothalamus or orexinergic fibers innervating raphe pallidus impaired or improved glucose tolerance, respectively. Collectively, the present study assigns orexin signaling in serotonergic neurons critical, yet differential orexin receptor type 1- and 2-dependent functions in the regulation of systemic glucose homeostasis.


Assuntos
Glucose/metabolismo , Obesidade/metabolismo , Receptores de Orexina/metabolismo , Neurônios Serotoninérgicos/metabolismo , Tecido Adiposo Marrom/metabolismo , Animais , Dieta Hiperlipídica/efeitos adversos , Homeostase , Região Hipotalâmica Lateral/citologia , Região Hipotalâmica Lateral/metabolismo , Resistência à Insulina , Fígado/metabolismo , Camundongos , Fibras Nervosas/metabolismo , Obesidade/etiologia , Receptores de Orexina/genética , Orexinas/metabolismo , Núcleos da Rafe/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/genética , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Transdução de Sinais
2.
Molecules ; 26(16)2021 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-34443437

RESUMO

Over 20 years ago, orexin neuropeptides (Orexin-A/hypocretin-1 and Orexin-B/hypocretins-2) produced from the same precursor in hypothalamus were identified. These two neurotransmitters and their receptors (OX1R and OX1R), present in the central and peripheral nervous system, play a major role in wakefulness but also in drug addiction, food consumption, homeostasis, hormone secretion, reproductive function, lipolysis and blood pressure regulation. With respect to these biological functions, orexins were involved in various pathologies encompassing narcolepsy, neurodegenerative diseases, chronic inflammations, metabolic syndrome and cancers. The expression of OX1R in various cancers including colon, pancreas and prostate cancers associated with its ability to induce a proapoptotic activity in tumor cells, suggested that the orexins/OX1R system could have a promising therapeutic role. The present review summarizes the relationship between cancers and orexins/OX1R system as an emerging target.


Assuntos
Terapia de Alvo Molecular , Neoplasias/metabolismo , Orexinas/metabolismo , Animais , Humanos , Modelos Biológicos , Receptores de Orexina/química , Receptores de Orexina/metabolismo , Orexinas/química , Transdução de Sinais
3.
Anesth Analg ; 133(3): 781-793, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34403389

RESUMO

BACKGROUND: Orexin, a neuropeptide derived from the perifornical area of the hypothalamus (PeFLH), promotes the recovery of propofol, isoflurane, and sevoflurane anesthesias, without influencing the induction time. However, whether the orexinergic system also plays a similar role in desflurane anesthesia, which is widely applied in clinical practice owing to its most rapid onset and offset time among all volatile anesthetics, has not yet been studied. In the present study, we explored the effect of the orexinergic system on the consciousness state induced by desflurane anesthesia. METHODS: The c-Fos staining was used to observe the activity changes of orexinergic neurons in the PeFLH and their efferent projection regions under desflurane anesthesia. Chemogenetic and optogenetic techniques were applied to compare the effect of PeFLH orexinergic neurons on the induction, emergence, and maintenance states between desflurane and isoflurane anesthesias. Orexinergic terminals in the paraventricular thalamic nucleus (PVT) were manipulated with pharmacologic, chemogenetic, and optogenetic techniques to assess the effect of orexinergic circuitry on desflurane anesthesia. RESULTS: Desflurane anesthesia inhibited the activity of orexinergic neurons in the PeFLH, as well as the neuronal activity in PVT, basal forebrain, dorsal raphe nucleus, and ventral tegmental area, as demonstrated by c-Fos staining. Activation of PeFLH orexinergic neurons prolonged the induction time and accelerated emergence from desflurane anesthesia but only influenced the emergence in isoflurane anesthesia, as demonstrated by chemogenetic and pharmacologic techniques. Meanwhile, optical activation of orexinergic neurons exhibited a long-lasting inhibitory effect on burst-suppression ratio (BSR) under desflurane anesthesia, and the effect may be contributed by the orexinergic PeFLH-PVT circuitry. The orexin-2 receptor (OX2R), but not orexin-1 receptor (OX1R), in the PVT, which had been inhibited most significantly by desflurane, mediated the proemergence effect of desflurane anesthesia. CONCLUSIONS: We discovered, for the first time, that orexinergic neurons in the PeFLH could not only influence the maintenance and emergence from isoflurane and desflurane anesthesias but also affect the induction under desflurane anesthesia. Furthermore, this specific effect is probably mediated by orexinergic PeFLH-PVT circuitry, especially OX2Rs in the PVT.


Assuntos
Período de Recuperação da Anestesia , Anestesia por Inalação , Anestésicos Inalatórios/farmacologia , Estado de Consciência/efeitos dos fármacos , Desflurano/farmacologia , Isoflurano/farmacologia , Núcleos da Linha Média do Tálamo/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Orexinas/farmacologia , Potenciais de Ação , Animais , Eletroencefalografia , Masculino , Núcleos da Linha Média do Tálamo/metabolismo , Neurônios/metabolismo , Optogenética , Receptores de Orexina/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos Sprague-Dawley , Fatores de Tempo
4.
Biomolecules ; 11(8)2021 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-34439801

RESUMO

The potential, multifaceted therapeutic profile of cannabidiol (CBD), a major constituent derived from the Cannabis sativa plant, covers a wide range of neurological and psychiatric disorders, ranging from anxiety to pediatric epilepsy and drug addiction. However, the molecular targets responsible for these effects have been only partially identified. In this view, the involvement of the orexin system, the key regulator in arousal and the sleep/wake cycle, and in motivation and reward processes, including drug addiction, prompted us to explore, using computational and experimental approaches, the possibility that CBD could act as a ligand of orexin receptors, orexin 1 receptor of type 1 (OX1R) and type 2 (OX2R). Ligand-binding assays showed that CBD is a selective ligand of OX1R in the low micromolar range (Ki 1.58 ± 0.2 µM) while in vitro functional assays, carried out by intracellular calcium imaging and mobilization assays, showed that CBD acts as an antagonist at this receptor. Finally, the putative binding mode of CBD has been inferred by molecular docking and molecular dynamics simulations and its selectivity toward the OX1R subtype rationalized at the molecular level. This study provides the first evidence that CBD acts as an OX1R antagonist, supporting its potential use in addictive disorders and/or body weight regulation.


Assuntos
Ansiolíticos/farmacologia , Anticonvulsivantes/farmacologia , Canabidiol/farmacologia , Receptores de Orexina/química , Orexinas/química , Animais , Ansiolíticos/química , Ansiolíticos/metabolismo , Anticonvulsivantes/química , Anticonvulsivantes/metabolismo , Sítios de Ligação , Células CHO , Cálcio/metabolismo , Canabidiol/química , Canabidiol/metabolismo , Cricetulus , Expressão Gênica , Humanos , Cinética , Simulação de Acoplamento Molecular , Imagem Molecular , Antagonistas dos Receptores de Orexina , Receptores de Orexina/genética , Receptores de Orexina/metabolismo , Orexinas/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Ensaio Radioligante , Transgenes
5.
Am J Physiol Regul Integr Comp Physiol ; 321(4): R558-R571, 2021 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-34405704

RESUMO

Orexin neurons are active in wakefulness and mostly silent in sleep. In adult rats and humans, orexin facilitates the hypercapnic ventilatory response but has little effect on resting ventilation. The influence of orexin on breathing in the early postnatal period, and across states of vigilance, have not been investigated. This is relevant as the orexin system may be impaired in Sudden Infant Death Syndrome (SIDS) cases. We addressed three hypotheses: 1) orexin provides a drive to breathe in infancy; 2) the effect of orexin depends on stage of postnatal development; and 3) orexin has a greater influence on breathing in wakefulness compared with sleep. Whole body plethysmography was used to monitor breathing of infant rats at three ages: postnatal days (P) 7-8, 12-14, and 17-19. Respiratory variables were analyzed in wakefulness (W), quiet sleep (QS), and active sleep (AS), following suvorexant (5 mg/kg ip), a dual orexin receptor antagonist, or vehicle (DMSO). Effects of suvorexant on ventilatory responses to graded hypercapnia ([Formula: see text] = 0.02, 0.04, 0.06), hypoxia ([Formula: see text] = 0.10), and hyperoxia ([Formula: see text] = 1.0) at P12-14 were also tested. At P12-14, but not at other ages, suvorexant significantly reduced respiratory frequency in all states, reduced the ventilatory equivalent in QW and QS, and increased [Formula: see text] to ∼5 mmHg. Suvorexant had no effect on ventilatory responses to graded hypercapnia or hypoxia. Hyperoxia eliminated the effects of suvorexant on respiratory frequency at P12-14. Our data suggest that orexin preserves eupneic frequency and ventilation in rats, specifically at ∼2 wk of age, perhaps by facilitating tonic peripheral chemoreflex activity.


Assuntos
Células Quimiorreceptoras/metabolismo , Pulmão/inervação , Orexinas/metabolismo , Ventilação Pulmonar , Reflexo , Mecânica Respiratória , Animais , Animais Recém-Nascidos , Azepinas/farmacologia , Células Quimiorreceptoras/efeitos dos fármacos , Hipercapnia/metabolismo , Hipercapnia/fisiopatologia , Hipóxia/metabolismo , Hipóxia/fisiopatologia , Antagonistas dos Receptores de Orexina/farmacologia , Receptores de Orexina/metabolismo , Ventilação Pulmonar/efeitos dos fármacos , Ratos Sprague-Dawley , Reflexo/efeitos dos fármacos , Mecânica Respiratória/efeitos dos fármacos , Sono , Triazóis/farmacologia , Vigília
6.
J Med Chem ; 64(12): 8806-8825, 2021 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-34101446

RESUMO

Loss of orexin-producing neurons results in narcolepsy with cataplexy, and orexin agonists have been shown to increase wakefulness and alleviate narcolepsy symptoms in animal models. Several OX2R agonists have been reported but with little or no activity at OX1R. We conducted structure-activity relationship studies on the OX2R agonist YNT-185 (2) and discovered dual agonists such as RTOXA-43 (40) with EC50's of 24 nM at both OX2R and OX1R. Computational modeling studies based on the agonist-bound OX2R cryogenic electron microscopy structures showed that 40 bound in the same binding pocket and interactions of the pyridylmethyl group of 40 with OX1R may have contributed to its high OX1R potency. Intraperitoneal injection of 40 increased time awake, decreased time asleep, and increased sleep/wake consolidation in 12-month old mice. This work provides a promising dual small molecule agonist and supports development of orexin agonists as potential treatments for orexin-deficient disorders such as narcolepsy.


Assuntos
Receptores de Orexina/agonistas , Sono/efeitos dos fármacos , Sulfonamidas/farmacologia , Vigília/efeitos dos fármacos , Animais , Células CHO , Cricetulus , Feminino , Masculino , Camundongos , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Estrutura Molecular , Receptores de Orexina/metabolismo , Relação Estrutura-Atividade , Sulfonamidas/síntese química , Sulfonamidas/metabolismo
7.
Neuroscience ; 468: 158-167, 2021 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-34126185

RESUMO

The ability to distinguish between threatening (repulsors), neutral and appetitive stimuli (attractors) stimuli is essential for survival. The orexinergic neurons of hypothalamus send projections to the limbic structures, such as different subregions of the medial prefrontal cortex (mPFC), suggesting that the orexinergic mechanism in the prelimbic cortex (PL) is involved in the processing of fear and anxiety. We investigated the role of orexin receptors type 1 (OX1R) and type 2 (OX2R) in the PL in such processes upon confrontation with an erratically moving robo-beetle in mice. The selective blockade of OX1R and OX2R in the PL with SB 334867 (3, 30, 300 nM) and TCS OX2 29 (3, 30, 300 nM), respectively, did not affect general exploratory behavior or reactive fear such as avoidance, jumping or freezing, but significantly enhances tolerance and approach behavior at the highest dose of each antagonist tested (300 nM). We interpret these findings as evidence for an altered cognitive appraisal of the potential threatening stimulus. Consequently, the orexin system seems to bias the perception of stimuli towards danger or threat via OX1R and OX2R in the PL.


Assuntos
Córtex Cerebral , Antagonistas dos Receptores de Orexina , Animais , Córtex Cerebral/metabolismo , Hipotálamo/metabolismo , Camundongos , Antagonistas dos Receptores de Orexina/farmacologia , Receptores de Orexina/metabolismo , Orexinas/metabolismo
8.
Int J Mol Sci ; 22(10)2021 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-34068146

RESUMO

Orexin A, an endogenous peptide involved in several functions including reward, acts via activation of orexin receptors OX1 and OX2, Gq-coupled GPCRs. We examined the effect of a selective OX1 agonist, OXA (17-33) on cytosolic calcium concentration, [Ca2+]i, in neurons of nucleus accumbens, an important area in the reward circuit. OXA (17-33) increased [Ca2+]i in a dose-dependent manner; the effect was prevented by SB-334867, a selective OX1 receptors antagonist. In Ca2+-free saline, the OXA (17-33)-induced increase in [Ca2+]i was not affected by pretreatment with bafilomycin A1, an endo-lysosomal calcium disrupter, but was blocked by 2-APB and xestospongin C, antagonists of inositol-1,4,5-trisphosphate (IP3) receptors. Pretreatment with VU0155056, PLD inhibitor, or BD-1047 and NE-100, Sigma-1R antagonists, reduced the [Ca2+]i response elicited by OXA (17-33). Cocaine potentiated the increase in [Ca2+]i by OXA (17-33); the potentiation was abolished by Sigma-1R antagonists. Our results support an additional signaling mechanism for orexin A-OX1 via choline-Sigma-1R and a critical role for Sigma-1R in the cocaine-orexin A interaction in nucleus accumbens neurons.


Assuntos
Colina/metabolismo , Cocaína/farmacologia , Neurônios/fisiologia , Núcleo Accumbens/fisiologia , Receptores de Orexina/metabolismo , Orexinas/metabolismo , Receptores sigma/metabolismo , Animais , Animais Recém-Nascidos , Regulação da Expressão Gênica , Neurônios/efeitos dos fármacos , Núcleo Accumbens/efeitos dos fármacos , Receptores de Orexina/genética , Orexinas/genética , Ratos , Ratos Sprague-Dawley , Receptores sigma/genética , Vasoconstritores/farmacologia
9.
Nat Commun ; 12(1): 2526, 2021 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-33953190

RESUMO

The prevalence of asthma and airway hyperreactivity (AHR) is increasing at an alarming rate. Group 2 innate lymphoid cells (ILC2s) are copious producers of type 2 cytokines, which leads to AHR and lung inflammation. Here, we show that mouse ILC2s express CD200 receptor (CD200R) and this expression is inducible. CD200R engagement inhibits activation, proliferation and type 2 cytokine production, indicating an immunoregulatory function for the CD200-CD200R axis on ILC2s. Furthermore, CD200R engagement inhibits both canonical and non-canonical NF-κB signaling pathways in activated ILC2s. Additionally, we demonstrate both preventative and therapeutic approaches utilizing CD200R engagement on ILC2s, which lead to improved airway resistance, dynamic compliance and eosinophilia. These results show CD200R is expressed on human ILC2s, and its engagement ameliorates AHR in humanized mouse models, emphasizing the translational applications for treatment of ILC2-related diseases such as allergic asthma.


Assuntos
Antígenos CD/metabolismo , Asma/metabolismo , Imunidade Inata/imunologia , Linfócitos/metabolismo , Receptores de Orexina/metabolismo , Pneumonia/metabolismo , Animais , Antígenos CD/genética , Asma/imunologia , Proliferação de Células , Citocinas/metabolismo , Proteínas de Ligação a DNA/genética , Modelos Animais de Doenças , Eosinofilia , Feminino , Humanos , Interleucina-33/metabolismo , Pulmão/metabolismo , Glicoproteínas de Membrana , Camundongos , Camundongos Endogâmicos BALB C , Receptores de Orexina/genética , Pneumonia/imunologia
10.
PLoS One ; 16(3): e0244770, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33780466

RESUMO

The inhibitory signaling of CD200 receptor 1 (CD200R) has been attributed to its NPxY signaling motif. However, NPxY-motifs are present in multiple protein families and are mostly known to mediate protein trafficking between subcellular locations rather than signaling. Therefore, we investigated whether additional motifs specify the inhibitory function of CD200R. We performed phylogenetic analysis of the intracellular domain of CD200R in mammals, birds, bony fish, amphibians and reptiles. Indeed, the tyrosine of the NPxY-motif is fully conserved across species, in line with its central role in CD200R signaling. In contrast, P295 of the NPxY-motif is not conserved. Instead, a conserved stretch of negatively charged amino acids, EEDE279, and two conserved residues P285 and K292 in the flanking region prior to the NPxY-motif are required for CD200R mediated inhibition of p-Erk, p-Akt308, p-Akt473, p-rpS6 and LPS-induced IL-8 secretion. Altogether, we show that instead of the more common NPxY-motif, CD200R signaling can be assigned to a unique signaling motif in mammals defined by: EEDExxPYxxYxxKxNxxY.


Assuntos
Receptores de Orexina/metabolismo , Transdução de Sinais , Motivos de Aminoácidos , Animais , Linhagem Celular , MAP Quinases Reguladas por Sinal Extracelular/antagonistas & inibidores , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Humanos , Interleucina-8/metabolismo , Lipopolissacarídeos/farmacologia , Monócitos/citologia , Monócitos/efeitos dos fármacos , Monócitos/metabolismo , Mutagênese Sítio-Dirigida , Receptores de Orexina/química , Receptores de Orexina/classificação , Receptores de Orexina/genética , Fosforilação , Filogenia , Domínios Proteicos , Proteínas Proto-Oncogênicas c-akt/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-akt/metabolismo , Tirosina/metabolismo
11.
Environ Pollut ; 278: 116887, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33743271

RESUMO

6-benzylaminopurine (6-BA) is one of the first synthetic hormones and has been widely used in fruit cultivation, gardening and agriculture. However, excessive use of 6-BA will cause potential harm to the environment and humans. Therefore, our research focused on assessing the impact of 6-BA on the development and neurobehavior of zebrafish. The results showed that 6-BA had little effect on the embryos from 2 hpf to 10 hpf. However, delayed development, decreased survival and hatchability were observed under 30 and 40 mg/L 6-BA from 24 hpf. 6-BA also reduced surface tension of embryonic chorions at 24 hpf. In addition, 6-BA caused abnormal morphology and promoted the accumulation of oxidative stress. Transcription of genes in connection with development and oxidative stress was also strikingly altered. Results of movement assay showed that zebrafish were less active and their behavior was significantly inhibited under the 20 and 30 mg/L 6-BA treatments. Locomotion-related genes th and mao were down-regulated by gradient, while the transcription of dbh was upregulated at a low concentration (2 mg/L) but decreased as the concentration increased. Moreover, 6-BA exposure caused increased arousal and decreased sleep. Sleep/wake related genes hcrt and hcrtr2 were upregulated, but decreased at 30 mg/L, while the mRNA level of aanat2 was reduced in a concentration-dependent manner. To sum up, our results showed that 6-BA induced developmental toxicity, promoted the accumulation of oxidative stress, and damaged locomotion and sleep/wake behavior.


Assuntos
Poluentes Químicos da Água , Peixe-Zebra , Animais , Compostos de Benzil/metabolismo , Embrião não Mamífero/metabolismo , Desenvolvimento Embrionário , Humanos , Receptores de Orexina/metabolismo , Estresse Oxidativo , Purinas/metabolismo , Poluentes Químicos da Água/metabolismo
12.
Theranostics ; 11(8): 3813-3829, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33664863

RESUMO

Background: Consolation behaviors toward the sick are common in humans. Anxiety in the relatives of the sick is also common. Anxiety can cause detrimental effects on multiple systems. However, our understanding on the neural mechanisms of these behaviors is limited because of the lack of small animal models. Methods: Five of 6- to 8-week-old CD-1 male mice were housed in a cage. Among them, 2 mice had right common artery exposure (surgery) and the rest were without surgery. Allo-grooming and performance in light and dark box and elevated plus maze tests of the mice were determined. Results: Mice without surgery had increased allo-grooming toward mice with surgery but decreased allo-grooming toward non-surgery intruders. This increased allo-grooming toward surgery mice was higher in familiar observers of surgery mice than that of mice that were not cage-mates of surgery mice before the surgery. Familiar observers developed anxious behavior after being with surgery mice. Surgery mice with familiar observers had less anxious behavior than surgery mice without interacting with familiar observers. Multiple brain regions including paraventricular thalamic nucleus (PVT) were activated in familiar observers. The activated cells in PVT contained orexin receptors. Injuring the neurons with ibotenic acid, antagonizing orexin signaling with an anti-orexin antibody or inhibiting neurons by chemogenetic approach in PVT abolished the consolation and anxious behaviors of familiar observers. Conclusions: Mice show consolation behavior toward the sick. This behavior attenuates the anxious behavior of surgery mice. The orexin signaling in the PVT neurons play a critical role in the consolation of familiar observers toward surgery mice and their anxious behavior. Considering that about 50 million patients have surgery annually in the United States, our study represents the initial attempt to understand neural mechanisms for consolation and anxiety of a large number of people.


Assuntos
Ansiedade/fisiopatologia , Comportamento Animal/fisiologia , Empatia/fisiologia , Núcleos da Linha Média do Tálamo/fisiologia , Animais , Ansiedade/prevenção & controle , Comportamento Animal/efeitos dos fármacos , Empatia/efeitos dos fármacos , Humanos , Interleucina-6/metabolismo , Masculino , Camundongos , Núcleos da Linha Média do Tálamo/efeitos dos fármacos , Modelos Animais , Modelos Neurológicos , Antagonistas dos Receptores de Orexina/administração & dosagem , Receptores de Orexina/metabolismo , Medicina de Precisão , Procedimentos Cirúrgicos Operatórios/efeitos adversos , Procedimentos Cirúrgicos Operatórios/psicologia
13.
Int J Mol Sci ; 22(4)2021 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-33562512

RESUMO

The molecule CD200, described many years ago as a naturally occurring immunomodulatory agent, capable of regulating inflammation and transplant rejection, has attracted additional interest over the past years with the realization that it may also serve as an important marker for progressive malignancy. A large body of evidence also supports the hypothesis that this molecule can contribute to immunoregulation of, among other diseases, infection, autoimmune disease and allergy. New data have also come to light to characterize the receptors for CD200 (CD200R) and their potential mechanism(s) of action at the biochemical level, as well as the description of a novel natural antagonist of CD200, lacking the NH2-terminal region of the full-length molecule. Significant controversies exist concerning the relative importance of CD200 as a ligand for all reported CD200Rs. Nevertheless, some progress has been made in the identification of the structural constraints determining the interaction between CD200 and CD200R, and this information has in turn proved of use in developing novel small molecule agonists/antagonists of the interaction. The review below highlights many of these newer findings, and attempts to place them in the broad context of our understanding of the role of CD200-CD200R interactions in a variety of human diseases.


Assuntos
Antígenos CD/metabolismo , Imunomodulação , Glicoproteínas de Membrana/metabolismo , Receptores de Orexina/metabolismo , Animais , Antígenos CD/genética , Antígenos CD/imunologia , Doenças Autoimunes/imunologia , Regulação da Expressão Gênica , Sobrevivência de Enxerto , Humanos , Sistema Imunitário/citologia , Sistema Imunitário/metabolismo , Imunomodulação/genética , Infecções/imunologia , Inflamação/imunologia , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/imunologia , Camundongos , Células Mieloides/imunologia , Células Mieloides/metabolismo , Neoplasias/imunologia , Receptores de Orexina/genética , Receptores de Orexina/imunologia , Domínios e Motivos de Interação entre Proteínas
14.
J Neurosci ; 41(12): 2566-2580, 2021 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-33536197

RESUMO

We show for the first time that the neuropeptide orexin modulates pupillary light response, a non-image-forming visual function, in mice of either sex. Intravitreal injection of the orexin receptor (OXR) antagonist TCS1102 and orexin-A reduced and enhanced pupillary constriction in response to light, respectively. Orexin-A activated OX1Rs on M2-type intrinsically photosensitive retinal ganglion cells (M2 cells), and caused membrane depolarization of these cells by modulating inward rectifier potassium channels and nonselective cation channels, thus resulting in an increase in intrinsic excitability. The increased intrinsic excitability could account for the orexin-A-evoked increase in spontaneous discharges and light-induced spiking rates of M2 cells, leading to an intensification of pupillary constriction. Orexin-A did not alter the light response of M1 cells, which could be because of no or weak expression of OX1Rs on them, as revealed by RNAscope in situ hybridization. In sum, orexin-A is likely to decrease the pupil size of mice by influencing M2 cells, thereby improving visual performance in awake mice via enhancing the focal depth of the eye's refractive system.SIGNIFICANCE STATEMENT This study reveals the role of the neuropeptide orexin in mouse pupillary light response, a non-image-forming visual function. Intravitreal orexin-A administration intensifies light-induced pupillary constriction via increasing the excitability of M2 intrinsically photosensitive retinal ganglion cells by activating the orexin receptor subtype OX1R. Modulation of inward rectifier potassium channels and nonselective cation channels were both involved in the ionic mechanisms underlying such intensification. Orexin could improve visual performance in awake mice by reducing the pupil size and thereby enhancing the focal depth of the eye's refractive system.


Assuntos
Orexinas/administração & dosagem , Estimulação Luminosa/métodos , Pupila/efeitos dos fármacos , Reflexo Pupilar/efeitos dos fármacos , Células Ganglionares da Retina/citologia , Células Ganglionares da Retina/efeitos dos fármacos , Animais , Benzimidazóis/administração & dosagem , Feminino , Injeções Intravítreas , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de Orexina/agonistas , Receptores de Orexina/metabolismo , Orexinas/antagonistas & inibidores , Pupila/fisiologia , Pirrolidinas/administração & dosagem , Reflexo Pupilar/fisiologia , Células Ganglionares da Retina/metabolismo
15.
Nat Commun ; 12(1): 815, 2021 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-33547286

RESUMO

Narcolepsy type 1 (NT1) is a chronic neurological disorder that impairs the brain's ability to control sleep-wake cycles. Current therapies are limited to the management of symptoms with modest effectiveness and substantial adverse effects. Agonists of the orexin receptor 2 (OX2R) have shown promise as novel therapeutics that directly target the pathophysiology of the disease. However, identification of drug-like OX2R agonists has proven difficult. Here we report cryo-electron microscopy structures of active-state OX2R bound to an endogenous peptide agonist and a small-molecule agonist. The extended carboxy-terminal segment of the peptide reaches into the core of OX2R to stabilize an active conformation, while the small-molecule agonist binds deep inside the orthosteric pocket, making similar key interactions. Comparison with antagonist-bound OX2R suggests a molecular mechanism that rationalizes both receptor activation and inhibition. Our results enable structure-based discovery of therapeutic orexin agonists for the treatment of NT1 and other hypersomnia disorders.


Assuntos
Aminopiridinas/química , Azepinas/química , Antagonistas dos Receptores de Orexina/química , Receptores de Orexina/química , Peptídeos/química , Medicamentos Indutores do Sono/química , Sulfonamidas/química , Triazóis/química , Aminopiridinas/metabolismo , Azepinas/metabolismo , Sítios de Ligação , Clonagem Molecular , Microscopia Crioeletrônica , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Células HEK293 , Humanos , Simulação de Dinâmica Molecular , Antagonistas dos Receptores de Orexina/metabolismo , Receptores de Orexina/agonistas , Receptores de Orexina/metabolismo , Peptídeos/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Medicamentos Indutores do Sono/metabolismo , Sulfonamidas/metabolismo , Triazóis/metabolismo
16.
Sci Rep ; 11(1): 231, 2021 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-33420199

RESUMO

Alcohol use disorder exhausts substantial social and economic costs, with recent dramatic increases in female problem drinking. Thus, it is critically important to understand signaling differences underlying alcohol consumption across the sexes. Orexin-1 receptors (Ox1Rs) can strongly promote motivated behavior, and we previously identified Ox1Rs within nucleus accumbens shell (shell) as crucial for driving binge intake in higher-drinking male mice. Here, shell Ox1R inhibition did not alter female mouse alcohol drinking, unlike in males. Also, lower dose systemic Ox1R inhibition reduced compulsion-like alcohol intake in both sexes, indicating that female Ox1Rs can drive some aspects of pathological consumption, and higher doses of systemic Ox1R inhibition (which might have more off-target effects) reduced binge drinking in both sexes. In contrast to shell Ox1Rs, inhibiting shell calcium-permeable AMPA receptors (CP-AMPARs) strongly reduced alcohol drinking in both sexes, which was specific to alcohol since this did not reduce saccharin intake in either sex. Our results together suggest that the shell critically regulates binge drinking in both sexes, with shell CP-AMPARs supporting intake in both sexes, while shell Ox1Rs drove drinking only in males. Our findings provide important new information about sex-specific and -general mechanisms that promote binge alcohol intake and possible targeted therapeutic interventions.


Assuntos
Consumo Excessivo de Bebidas Alcoólicas/metabolismo , Núcleo Accumbens/metabolismo , Receptores de Orexina/metabolismo , Receptores de AMPA/metabolismo , Animais , Feminino , Masculino , Camundongos , Caracteres Sexuais
17.
J Physiol ; 599(1): 231-252, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-32997815

RESUMO

KEY POINTS: Rhythmic processes in living organisms are controlled by biological clocks. The orexinergic system of the lateral hypothalamus carries circadian information to provide arousal for the brain during the active phase. Here, we show that orexins exert an excitatory action in three parts of the lateral geniculate nucleus (LGN), in particular upon directly retinorecipient neurons in the non-image forming visual structures. We provide evidence for the high nocturnal levels of orexins with stable circadian expression of predominant orexin receptor 2 in the LGN. Our data additionally establish the convergence of orexinergic and pituitary adenylate cyclase (PAC)-activating peptide/PAC1 receptor systems (used by melanopsin-expressing retinal ganglion cells), which directly regulates responses to the retinal input. These results help us better understand circadian orexinergic control over the non-image forming subcortical visual system, forming the animal's preparedness for the behaviourally active night. ABSTRACT: The orexinergic system of the lateral hypothalamus is tightly interlinked with the master circadian clock and displays daily variation in activity to provide arousal-related excitation for the plethora of brain structures in a circadian manner. Here, using a combination of electrophysiological, optogenetic, histological, molecular and neuronal tracing methods, we explore a particular link between orexinergic and visual systems in rat. The results of the present study demonstrate that orexinergic fibre density at the area of subcortical visual system exerts a clear day to night variability, reaching a maximum at behaviourally active night. We also show pronounced electrophysiological activations of neurons in the lateral geniculate nucleus by orexin A through 24 h, via identified distinct orexin receptors, with the ventrolateral geniculate displaying a daily cycle of responsiveness. In addition, for the first time, we provide a direct evidence for orexins to act on retinorecipient neurons with a high convergence of orexinergic and putatively retinal pituitary adenylate cyclase (PAC)-activating peptide/PAC1 receptor systems. Altogether, the present study ties orexins to non-image forming visual structures with implications for circadian orexinergic modulation of neurons, which process information on ambient light levels.


Assuntos
Corpos Geniculados , Neurônios , Animais , Ritmo Circadiano , Região Hipotalâmica Lateral/metabolismo , Neurônios/metabolismo , Receptores de Orexina/metabolismo , Orexinas/metabolismo , Ratos
18.
Life Sci ; 265: 118777, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33220293

RESUMO

The dorsal raphe nucleus (DRN) is a brainstem nucleus involved in the pathophysiology of the depression, through its serotoninergic innervation. Furthermore, depressive symptoms in patients are also associated with some memory and sleep complaints. Anatomical evidence confirmed the presence of projections from the lateral hypothalamus to serotonergic neurons of the dorsal raphe nucleus (DRN). These projection fibers release orexin neuropeptides which play roles in the spatial memory. Both of the orexinergic receptors are widely distributed in dorsal raphe nucleus. Therefore, the present work was aimed to assess the probable roles of orexin 1 and 2 receptors using an orexin 1 receptor antagonist, SB-334867-A, and an orexin 2 receptor antagonist, TCS-OX2-29 in the DRN on the retrieval, and consolidation phases of spatial reference memory in the Morris water maze (MWM) task. The results demonstrated that blocking orexin 1 receptors in the DRN impairs the process of memory consolidation in the spatial MWM via increasing in the time of the escape latency of the probe day. Blocking these receptors did not affect the retrieval phase of MWM learning. Furthermore, blocking of the orexin 2 receptors in this area did not affect neither consolidation nor retrieval phases of the memory. In conclusion, orexin 1 receptors in the DRN play major roles in the consolidation of the spatial reference memory in rats.


Assuntos
Núcleo Dorsal da Rafe/fisiologia , Receptores de Orexina/fisiologia , Memória Espacial/fisiologia , Animais , Benzoxazóis/farmacologia , Núcleo Dorsal da Rafe/efeitos dos fármacos , Masculino , Teste do Labirinto Aquático de Morris/efeitos dos fármacos , Teste do Labirinto Aquático de Morris/fisiologia , Naftiridinas/farmacologia , Antagonistas dos Receptores de Orexina/farmacologia , Receptores de Orexina/efeitos dos fármacos , Receptores de Orexina/metabolismo , Ratos , Memória Espacial/efeitos dos fármacos , Ureia/análogos & derivados , Ureia/farmacologia
19.
J Alzheimers Dis ; 79(2): 693-708, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33361602

RESUMO

BACKGROUND: Sleep/wake disturbances (e.g., insomnia and sleep fragmentation) are common in neurodegenerative disorders, especially Alzheimer's disease (AD) and frontotemporal dementia (FTD). These symptoms are somewhat reminiscent of narcolepsy with cataplexy, caused by the loss of orexin-producing neurons. A bidirectional relationship between sleep disturbance and disease pathology suggests a detrimental cycle that accelerates disease progression and cognitive decline. The accumulation of brain tau fibrils is a core pathology of AD and FTD-tau and clinical evidence supports that tau may impair the orexin system in AD/FTD. This hypothesis was investigated using tau mutant mice. OBJECTIVE: To characterize orexin receptor mRNA expression in sleep/wake regulatory brain centers and quantify noradrenergic locus coeruleus (LC) and orexinergic lateral hypothalamus (LH) neurons, in tau transgenic rTg4510 and tau-/- mice. METHODS: We used i n situ hybridization and immunohistochemistry (IHC) in rTg4510 and tau-/- mice. RESULTS: rTg4510 and tau-/- mice exhibited a similar decrease in orexin receptor 1 (OX1R) mRNA expression in the LC compared with wildtype controls. IHC data indicated this was not due to decreased numbers of LC tyrosine hydroxylase-positive (TH) or orexin neurons and demonstrated that tau invades TH LC and orexinergic LH neurons in rTg4510 mice. In contrast, orexin receptor 2 (OX2R) mRNA levels were unaffected in either model. CONCLUSION: The LC is strongly implicated in the regulation of sleep/wakefulness and expresses high levels of OX1R. These findings raise interesting questions regarding the effects of altered tau on the orexin system, specifically LC OX1Rs, and emphasize a potential mechanism which may help explain sleep/wake disturbances in AD and FTD.


Assuntos
Nível de Alerta , Locus Cerúleo/metabolismo , Receptores de Orexina/metabolismo , Proteínas tau/metabolismo , Animais , Feminino , Região Hipotalâmica Lateral/metabolismo , Hibridização In Situ , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , RNA Mensageiro/metabolismo
20.
Brain Behav ; 10(12): e01882, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33067924

RESUMO

OBJECTIVE: To study how the CD200-CD200R1 signaling pathway modulates poststroke inflammation and advances our knowledge of immune responses to ischemia insults in stroke. METHODS: Focal middle cerebral artery occlusion (MCAO) was induced in mice for 90 min, and mice were sacrificed at 1, 3, and 7 days of reperfusion. CD200, CD200R1, iNOS, and Arg-1 expression in ischemic brains was assessed by Western blotting (WB), and immunohistochemical (IHC) staining was performed to examine the expression of CD200 on neurons and CD200R1 on infiltrating lymphocytes. The severity of neurobehavioral deficits was evaluated by neurological deficit scores (NDS) and infarction volume estimated by TTC staining. To study the relationship between CD200/CD200R1 expression and the diversity of the neuroinflammatory response in stroke, CD200Fc (CD200R1 agonist) was subcutaneously injected at onset, at 1 day and 2 days after MCAO operation, and the brains were collected for detection at 3 days after MCAO/R (reperfusion). RESULTS: CD200 expression on neurons increased at 1 day and then decreased at 3 days after MCAO/R, and the expression of CD200R1 on lymphocytes showed an opposite temporal pattern as tested by IHC. The WB results showed that CD200/CD200R1 variance exhibited a similar pattern of IHC results, and the level of iNOS peaked at 1 day and then decreased gradually, but Arg-1 increased with time after MCAO/R in ischemic brains. After CD200Fc injection, CD200R1 expression significantly increased, and CD200Fc promoted Arg-1 but inhibited iNOS expression. The infarct volume and NDS of the group treated with CD200Fc were significantly smaller than those of the IgG2a-treated group. CONCLUSIONS: The CD200-CD200R1 signaling pathway regulates neuroinflammation after stroke. Stimulation of CD200R1 by CD200Fc promotes the anti-inflammatory response and alleviates ischemic injury.


Assuntos
Transdução de Sinais , Acidente Vascular Cerebral , Animais , Encéfalo/metabolismo , Inflamação , Camundongos , Receptores de Orexina/metabolismo
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