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Bohid S, Ali LK, Romero-Leguizamón CR, Langkilde AE, Dos Santos AB, Kohlmeier KA. Sex-dependent effects of monomeric α-synuclein on calcium and cell death of lateral hypothalamic mouse neurons are altered by orexin. Mol Cell Neurosci 2024; 129:103934. [PMID: 38701995 DOI: 10.1016/j.mcn.2024.103934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 03/25/2024] [Accepted: 04/28/2024] [Indexed: 05/06/2024] Open
Abstract
Parkinson's Disease (PD) patients experience sleeping disorders in addition to the disease-defining symptomology of movement dysfunctions. The prevalence of PD is sex-based and presence of sleeping disorders in PD also shows sex bias with a stronger phenotype in males. In addition to loss of dopamine-containing neurons in the striatum, arousal-related, orexin-containing neurons in the lateral hypothalamus (LH) are lost in PD, which could contribute to state-related disorders. As orexin has been shown to be involved in sleeping disorders and to have neuroprotective effects, we asked whether orexin could protect sleep-related LH neurons from damage putatively from the protein α-synuclein (α-syn), which is found at high levels in the PD brain and that we have shown is associated with putatively excitotoxic rises in intracellular calcium in brainstem sleep-controlling nuclei, especially in males. Accordingly, we monitored intracellular calcium transients induced by α-syn and whether concurrent exposure to orexin affected those transients in LH cells of the mouse brain slice using calcium imaging. Further, we used an assay of cell death to determine whether LH cell viability was influenced when α-syn and orexin were co-applied when compared to exposure to α-syn alone. We found that excitatory calcium events induced by α-syn were reduced in amplitude and frequency when orexin was co-applied, and when data were evaluated by sex, this effect was found to be greater in females. In addition, α-syn exposure was associated with cell death that was higher in males, and interestingly, reduced cell death was noted when orexin was present, which did not show a sex bias. We interpret our findings to indicate that orexin is protective to α-syn-mediated damage to hypothalamic neurons, and the actions of orexin on α-syn-induced cellular effects differ between sexes, which could underlie sex-based differences in sleeping disorders in PD.
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Affiliation(s)
- Sara Bohid
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Lara Kamal Ali
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Cesar Ramon Romero-Leguizamón
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark.
| | - Annette E Langkilde
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark.
| | - Altair Brito Dos Santos
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Kristi A Kohlmeier
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark.
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2
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Leino TO, Turku A, Urvas L, Adhikari K, Oksanen J, Steynen Y, Yli-Kauhaluoma J, Xhaard H, Kukkonen JP, Wallén EAA. Azulene as a biphenyl mimetic in orexin/hypocretin receptor agonists. Bioorg Med Chem 2023; 88-89:117325. [PMID: 37209639 DOI: 10.1016/j.bmc.2023.117325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 04/26/2023] [Accepted: 05/05/2023] [Indexed: 05/22/2023]
Abstract
Azulene is a rare ring structure in drugs, and we investigated whether it could be used as a biphenyl mimetic in known orexin receptor agonist Nag 26, which is binding to both orexin receptors OX1 and OX2 with preference towards OX2. The most potent azulene-based compound was identified as an OX1 orexin receptor agonist (pEC50 = 5.79 ± 0.07, maximum response = 81 ± 8% (s.e.m. of five independent experiments) of the maximum response to orexin-A in Ca2+ elevation assay). However, the azulene ring and the biphenyl scaffold are not identical in their spatial shape and electron distribution, and their derivatives may adopt different binding modes in the binding site.
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Affiliation(s)
- Teppo O Leino
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland; Department of Chemistry and NanoScience Center, University of Jyväskylä, P.O. Box 35, FI-40014 University of Jyväskylä, Finland.
| | - Ainoleena Turku
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland; Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, FI-00014 University of Helsinki, Finland
| | - Lauri Urvas
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland; Department of Pharmacology, Faculty of Medicine, University of Helsinki, P.O. Box 63, FI-00014 University of Helsinki, Finland
| | - Karuna Adhikari
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland
| | - Jouni Oksanen
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland
| | - Yana Steynen
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland
| | - Jari Yli-Kauhaluoma
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland
| | - Henri Xhaard
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland
| | - Jyrki P Kukkonen
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, FI-00014 University of Helsinki, Finland; Department of Pharmacology, Faculty of Medicine, University of Helsinki, P.O. Box 63, FI-00014 University of Helsinki, Finland
| | - Erik A A Wallén
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland
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Chatterjee O, Gopalakrishnan L, Pullimamidi D, Raj C, Yelamanchi S, Gangadharappa BS, Nair B, Mahadevan A, Raju R, Keshava Prasad TS. A molecular network map of orexin-orexin receptor signaling system. J Cell Commun Signal 2023; 17:217-227. [PMID: 36480100 PMCID: PMC10030760 DOI: 10.1007/s12079-022-00700-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 09/04/2022] [Accepted: 09/15/2022] [Indexed: 12/13/2022] Open
Abstract
Orexins are excitatory neuropeptides, which are predominantly associated with feeding behavior, sleep-wake cycle and energy homeostasis. The orexinergic system comprises of HCRTR1 and HCRTR2, G-protein-coupled receptors of rhodopsin family and the endogenous ligands processed from HCRT pro-hormone, Orexin A and Orexin B. These neuropeptides are biosynthesized by the orexin neurons present in the lateral hypothalamus area, with dense projections to other brain regions. The orexin-receptor signaling is implicated in various metabolic as well as neurological disorders, making it a promising target for pharmacological interventions. However, there is limited information available on the collective representation of the signal transduction pathways pertaining to the orexin-orexin receptor signaling system. Here, we depict a compendium of the Orexin A/B stimulated reactions in the form of a basic signaling pathway map. This map catalogs the reactions into five categories: molecular association, activation/inhibition, catalysis, transport, and gene regulation. A total of 318 downstream molecules were annotated adhering to the guidelines of NetPath curation. This pathway map can be utilized for further assessment of signaling events associated with orexin-mediated physiological functions and is freely available on WikiPathways, an open-source pathway database ( https://www.wikipathways.org/index.php/Pathway:WP5094 ).
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Affiliation(s)
- Oishi Chatterjee
- Institute of Bioinformatics, International Tech Park, 560 066, Bangalore, India
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, 690 525, Kollam, India
- Center for Systems Biology and Molecular Medicine, Yenepoya Research Centre, Yenepoya (Deemed to be University), 575 018, Mangalore, India
| | - Lathika Gopalakrishnan
- Institute of Bioinformatics, International Tech Park, 560 066, Bangalore, India
- Center for Systems Biology and Molecular Medicine, Yenepoya Research Centre, Yenepoya (Deemed to be University), 575 018, Mangalore, India
- Manipal Academy of Higher Education (MAHE), 576 104, Manipal, India
| | | | - Chinmayi Raj
- Institute of Bioinformatics, International Tech Park, 560 066, Bangalore, India
| | - Soujanya Yelamanchi
- Institute of Bioinformatics, International Tech Park, 560 066, Bangalore, India
| | | | - Bipin Nair
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, 690 525, Kollam, India
| | - Anita Mahadevan
- Human Brain Tissue Repository, Neurobiology Research Centre, National Institute of Mental Health and Neurosciences, 560 029, Bangalore, India
- Department of Neuropathology, Neurobiology Research Centre, National Institute of Mental Health and Neurosciences, 560 029, Bangalore, India
| | - Rajesh Raju
- Center for Systems Biology and Molecular Medicine, Yenepoya Research Centre, Yenepoya (Deemed to be University), 575 018, Mangalore, India.
| | - T S Keshava Prasad
- Center for Systems Biology and Molecular Medicine, Yenepoya Research Centre, Yenepoya (Deemed to be University), 575 018, Mangalore, India.
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4
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Bigalke JA, Shan Z, Carter JR. Orexin, Sleep, Sympathetic Neural Activity, and Cardiovascular Function. Hypertension 2022; 79:2643-2655. [PMID: 36148653 PMCID: PMC9649879 DOI: 10.1161/hypertensionaha.122.19796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Inadequate sleep duration and quality are associated with reduced cardiovascular health and increased mortality. Experimental evidence points to the sympathetic nervous system as a key mediator in the observed relationship between poor sleep and cardiovascular dysfunction. However, brain mechanisms underpinning the impaired sympathetic function associated with poor sleep remain unclear. Recent evidence suggests the central orexin system, particularly orexins A and B and their receptors, have a key regulatory role for sleep in animal and human models. While orexin system activity has been observed to significantly impact sympathetic regulation in animals, the extension of these findings to humans has been difficult due to an inability to directly assess orexin system activity in humans. However, direct measures of sympathetic activity in populations with narcolepsy and chronic insomnia, 2 sleep disorders associated with deficient and excessive orexin neural activity, have allowed indirect assessment of the relationships between orexin, sleep, and sympathetic regulation. Further, the recent pharmaceutical development of dual orexin receptor antagonists for use in clinical insomnia populations offers an unprecedented opportunity to examine the mechanistic role of orexin in sleep and cardiovascular health in humans. The current review assesses the role of orexin in both sleep and sympathetic regulation from a translational perspective, spanning animal and human studies. The review concludes with future research directions necessary to fully elucidate the mechanistic role for orexin in sleep and sympathetic regulation in humans.
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Affiliation(s)
- Jeremy A. Bigalke
- Department of Health and Human Development, Montana State University, Bozeman, Montana
- Department of Psychology, Montana State University, Bozeman, Montana
| | - Zhiying Shan
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, Michigan
| | - Jason R. Carter
- Department of Health and Human Development, Montana State University, Bozeman, Montana
- Department of Psychology, Montana State University, Bozeman, Montana
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5
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Kaplan GB, Lakis GA, Zhoba H. Sleep-Wake and Arousal Dysfunctions in Post-Traumatic Stress Disorder:Role of Orexin Systems. Brain Res Bull 2022; 186:106-122. [PMID: 35618150 DOI: 10.1016/j.brainresbull.2022.05.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 04/20/2022] [Accepted: 05/10/2022] [Indexed: 12/15/2022]
Abstract
Post-traumatic stress disorder (PTSD) is a trauma-related condition that produces distressing fear memory intrusions, avoidance behaviors, hyperarousal/startle, stress responses and insomnia. This review focuses on the importance of the orexin neural system as a novel mechanism related to the pathophysiology of PTSD. Orexinergic neurons originate in the lateral hypothalamus and project widely to key neurotransmitter system neurons, autonomic neurons, the hypothalamic-pituitaryadrenal (HPA) axis, and fear-related neural circuits. After trauma or stress, the basolateral amygdala (BLA) transmits sensory information to the central nucleus of the amygdala (CeA) and in turn to the hypothalamus and other subcortical and brainstem regions to promote fear and threat. Orexin receptors have a prominent role in this circuit as fear conditioned orexin receptor knockout mice show decreased fear expression while dual orexin receptor antagonists (DORAs) inhibit fear acquisition and expression. Orexin activation of an infralimbic-amygdala circuit impedes fear extinction while DORA treatments enhance it. Increased orexin signaling to the amygdalocortical- hippocampal circuit promotes avoidance behaviors. Orexin has an important role in activating sympathetic nervous system (SNS) activity and the HPA axis stress responses. Blockade of orexin receptors reduces fear-conditioned startle responses. In PTSD models, individuals demonstrate sleep disturbances such as increased sleep latency and more transitions to wakefulness. Increased orexin activity impairs sleep by promoting wakefulness and reducing total sleep time while DORA treatments enhance sleep onset and maintenance. The orexinergic neural system provides important mechanisms for understanding multiple PTSD behaviors and provides new medication targets to treat this often persistent and debilitating illness.
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Affiliation(s)
- Gary B Kaplan
- Mental Health Service, VA Boston Healthcare System, West Roxbury, MA, 02132 USA; Department of Psychiatry, Boston University School of Medicine, Boston, MA, 02118 USA; Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, 02118 USA.
| | - Gabrielle A Lakis
- Research Service, VA Boston Healthcare System, West Roxbury, MA, 02132 USA; Undergraduate Program in Neuroscience, Boston University, Boston, MA, 02215 USA
| | - Hryhoriy Zhoba
- Research Service, VA Boston Healthcare System, West Roxbury, MA, 02132 USA
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6
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Dale NC, Hoyer D, Jacobson LH, Pfleger KDG, Johnstone EKM. Orexin Signaling: A Complex, Multifaceted Process. Front Cell Neurosci 2022; 16:812359. [PMID: 35496914 PMCID: PMC9044999 DOI: 10.3389/fncel.2022.812359] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 03/07/2022] [Indexed: 11/15/2022] Open
Abstract
The orexin system comprises two G protein-coupled receptors, OX1 and OX2 receptors (OX1R and OX2R, respectively), along with two endogenous agonists cleaved from a common precursor (prepro-orexin), orexin-A (OX-A) and orexin-B (OX-B). For the receptors, a complex array of signaling behaviors has been reported. In particular, it becomes obvious that orexin receptor coupling is very diverse and can be tissue-, cell- and context-dependent. Here, the early signal transduction interactions of the orexin receptors will be discussed in depth, with particular emphasis on the direct G protein interactions of each receptor. In doing so, it is evident that ligands, additional receptor-protein interactions and cellular environment all play important roles in the G protein coupling profiles of the orexin receptors. This has potential implications for our understanding of the orexin system’s function in vivo in both central and peripheral environments, as well as the development of novel agonists, antagonists and possibly allosteric modulators targeting the orexin system.
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Affiliation(s)
- Natasha C. Dale
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Nedlands, WA, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Melbourne, VIC, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Perth, WA, Australia
| | - Daniel Hoyer
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
- Department of Biochemistry and Pharmacology, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, Australia
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, United States
| | - Laura H. Jacobson
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
- Department of Biochemistry and Pharmacology, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, Australia
- Melbourne Dementia Research Centre, Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, Australia
| | - Kevin D. G. Pfleger
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Nedlands, WA, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Melbourne, VIC, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Perth, WA, Australia
- Dimerix Limited, Nedlands, WA, Australia
- *Correspondence: Kevin D. G. Pfleger,
| | - Elizabeth K. M. Johnstone
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Nedlands, WA, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Melbourne, VIC, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Perth, WA, Australia
- School of Biomedical Sciences, The University of Western Australia, Nedlands, WA, Australia
- Elizabeth K. M. Johnstone,
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7
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Kourosh-Arami M, Kaeidi A, Semnanian S. Extracellular Calcium Contributes to Orexin-Induced Postsynaptic Excitation of the Rat Locus Coeruleus Neurons. Int J Pept Res Ther 2022. [DOI: 10.1007/s10989-022-10379-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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8
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Matzeu A, Martin-Fardon R. Understanding the Role of Orexin Neuropeptides in Drug Addiction: Preclinical Studies and Translational Value. Front Behav Neurosci 2022; 15:787595. [PMID: 35126069 PMCID: PMC8811192 DOI: 10.3389/fnbeh.2021.787595] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 12/29/2021] [Indexed: 12/22/2022] Open
Abstract
Orexins (also known as hypocretins) are neuropeptides that participate in the regulation of energy metabolism, homeostasis, sleep, feeding, stress responses, arousal, and reward. Particularly relevant to the scope of the present review is the involvement of the orexin system in brain mechanisms that regulate motivation, especially highly motivated behavior, arousal, and stress, making it an ideal target for studying addiction and discovering treatments. Drug abuse and misuse are thought to induce maladaptive changes in the orexin system, and these changes might promote and maintain uncontrolled drug intake and contribute to relapse. Dysfunctional changes in this neuropeptidergic system that are caused by drug use might also be responsible for alterations of feeding behavior and the sleep-wake cycle that are commonly disrupted in subjects with substance use disorder. Drug addiction has often been associated with an increase in activity of the orexin system, suggesting that orexin receptor antagonists may be a promising pharmacological treatment for substance use disorder. Substantial evidence has shown that single orexin receptor antagonists that are specific to either orexin receptor 1 or 2 can be beneficial against drug intake and relapse. Interest in the efficacy of dual orexin receptor antagonists, which were primarily developed to treat insomnia, has grown in the field of drug addiction. Treatments that target the orexin system may be a promising strategy to reduce drug intake, mitigate relapse vulnerability, and restore “normal” physiological functions, including feeding and sleep. The present review discusses preclinical and clinical evidence of the involvement of orexins in drug addiction and possible beneficial pharmacotherapeutic effects of orexin receptor antagonists to treat substance use disorder.
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Coleman P, de Lecea L, Gotter A, Hagan J, Hoyer D, Kilduff T, Kukkonen JP, Porter R, Renger J, Siegel JM, Sutcliffe G, Upton N, Winrow CJ. Orexin receptors in GtoPdb v.2021.3. IUPHAR/BPS GUIDE TO PHARMACOLOGY CITE 2021; 2021. [PMID: 34927075 DOI: 10.2218/gtopdb/f51/2021.3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Orexin receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Orexin receptors [42]) are activated by the endogenous polypeptides orexin-A and orexin-B (also known as hypocretin-1 and -2; 33 and 28 aa) derived from a common precursor, preproorexin or orexin precursor, by proteolytic cleavage and some typical peptide modifications [109]. Currently the only orexin receptor ligands in clinical use are suvorexant and lemborexant, which are used as hypnotics. Orexin receptor crystal structures have been solved [134, 133, 54, 117, 46].
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10
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Fan Y, Jiang E, Gao H, Bigalke J, Chen B, Yu C, Chen Q, Shan Z. Activation of Orexin System Stimulates CaMKII Expression. Front Physiol 2021; 12:698185. [PMID: 34276418 PMCID: PMC8282234 DOI: 10.3389/fphys.2021.698185] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 06/08/2021] [Indexed: 11/18/2022] Open
Abstract
Hyperactivity of the orexin system within the paraventricular nucleus (PVN) has been shown to contribute to increased sympathetic nerve activity (SNA) and blood pressure (BP) in rodent animals. However, the underlying molecular mechanisms remain unclear. Here, we test the hypothesis that orexin system activation stimulates calcium/calmodulin-dependent kinase II (CaMKII) expression and activation, and stimulation of CaMKII expressing PVN neurons increases SNA and BP. Real-time PCR and/or western blot were carried out to test the effect of orexin-A administration on CaMKII expression in the PVN of normal Sprague Dawley (SD) rats and orexin receptor 1 (OX1R) expressing PC12 cells. Immunostaining was performed to assess OX1R cellular localization in the PVN of SD rats as well as orexin-A treatment on CaMKII activation in cultured hypothalamic neurons. In vivo sympathetic nerve recordings were employed to test the impact of optogenetic stimulation of CaMKII-expressing PVN neurons on the renal SNA (RSNA) and BP. The results showed that intracerebroventricular injection of orexin-A into the SD rat increases mRNA expression of CaMKII subunits in the PVN. In addition, Orexin-A treatment increases CaMKII expression and its phosphorylation in OX1R-expressing PC12 cells. Furthermore, Orexin-A treatment increases CaMKII activation in cultured hypothalamic neurons from neonatal SD rats. Finally, optogenetic excitation of PVN CaMKII-expressing neurons results in robust increases in RSNA and BP in SD rats. Our results suggest that increased orexin system activity activates CaMKII expression in cardiovascular relevant regions, and this may be relevant to the downstream cardiovascular effects of CaMKII.
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Affiliation(s)
- Yuanyuan Fan
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI, United States.,School of Life Sciences, Henan University, Kaifeng, China
| | - Enshe Jiang
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI, United States.,Institute of Nursing and Health, Henan University, Kaifeng, China
| | - Huanjia Gao
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI, United States.,The Second Clinical College, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Jeremy Bigalke
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI, United States
| | - Bojun Chen
- Department of Emergency, The Second Affiliated Hospital, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Chunxiu Yu
- Health Research Institute, Michigan Technological University, Houghton, MI, United States.,Department of Biological Sciences, Michigan Technological University, Houghton, MI, United States
| | - Qinghui Chen
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI, United States.,Health Research Institute, Michigan Technological University, Houghton, MI, United States
| | - Zhiying Shan
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI, United States.,Health Research Institute, Michigan Technological University, Houghton, MI, United States
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11
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Elam HB, Perez SM, Donegan JJ, Lodge DJ. Orexin receptor antagonists reverse aberrant dopamine neuron activity and related behaviors in a rodent model of stress-induced psychosis. Transl Psychiatry 2021; 11:114. [PMID: 33558469 PMCID: PMC7870676 DOI: 10.1038/s41398-021-01235-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 01/08/2021] [Accepted: 01/18/2021] [Indexed: 12/15/2022] Open
Abstract
Post-traumatic stress disorder (PTSD) is a prevalent condition affecting approximately 8% of the United States population and 20% of United States combat veterans. In addition to core symptoms of the disorder, up to 64% of individuals diagnosed with PTSD experience comorbid psychosis. Previous research has demonstrated a positive correlation between symptoms of psychosis and increases in dopamine transmission. We have recently demonstrated projections from the paraventricular nucleus of the thalamus (PVT) to the nucleus accumbens (NAc) can regulate dopamine neuron activity in the ventral tegmental area (VTA). Specifically, inactivation of the PVT leads to a reversal of aberrant dopamine system function and psychosis-like behavior. The PVT receives dense innervation from orexin containing neurons, therefore, targeting orexin receptors may be a novel approach to restore dopamine neuron activity and alleviate PTSD-associated psychosis. In this study, we induced stress-related pathophysiology in male Sprague Dawley rats using an inescapable foot-shock procedure. We observed a significant increase in VTA dopamine neuron population activity, deficits in sensorimotor gating, and hyperresponsivity to psychomotor stimulants. Administration of selective orexin 1 receptor (OX1R) and orexin 2 receptor (OX2R) antagonists (SB334867 and EMPA, respectively) or the FDA-approved, dual-orexin receptor antagonist, Suvorexant, were found to reverse stress-induced increases in dopamine neuron population activity. However, only Suvorexant and SB334867 were able to reverse deficits in behavioral corelates of psychosis. These results suggest that the orexin system may be a novel pharmacological target for the treatment of comorbid psychosis related to PTSD.
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Affiliation(s)
- Hannah B Elam
- Department of Pharmacology and Center for Biomedical Neuroscience, University of Texas Health Science Center, San Antonio, TX, 78229, USA.
| | - Stephanie M Perez
- Department of Pharmacology and Center for Biomedical Neuroscience, University of Texas Health Science Center, San Antonio, TX, 78229, USA
| | - Jennifer J Donegan
- Department of Pharmacology and Center for Biomedical Neuroscience, University of Texas Health Science Center, San Antonio, TX, 78229, USA
| | - Daniel J Lodge
- Department of Pharmacology and Center for Biomedical Neuroscience, University of Texas Health Science Center, San Antonio, TX, 78229, USA
- South Texas Veterans Health Care System, Audie L. Murphy Division, San Antonio, USA
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12
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Yaeger JD, Krupp KT, Gale JJ, Summers CH. Counterbalanced microcircuits for Orx1 and Orx2 regulation of stress reactivity. MEDICINE IN DRUG DISCOVERY 2020. [DOI: 10.1016/j.medidd.2020.100059] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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13
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Phospholipase Cβ3 in the hippocampus may mediate impairment of memory by long-term blockade of orexin 1 receptors assessed by the Morris water maze. Life Sci 2020; 257:118046. [PMID: 32622948 DOI: 10.1016/j.lfs.2020.118046] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/19/2020] [Accepted: 06/30/2020] [Indexed: 11/23/2022]
Abstract
Orexin-A is an endogenous peptide with receptors throughout the brain. According to some recent research, learning and memory are affected by the central administration of orexin; however, no study so far has investigated the long-term inhibition of the orexinergic system. The present study has evaluated the effect of pretraining administration of orexin 1 receptor (OXR1) antagonist, SB-334867, on the acquisition of memory. The Morris water maze (MWM) task was used for training and trial purposes in all groups. Memory performance was analyzed by measuring escape latency, traveled distance, and time spent in the target quadrant. Moreover, the effect of SB-334867 on phospholipase Cβ3 (PLCβ3) levels in the CA1 region of hippocampus slices was examined. Hippocampus slices were prepared using an immunohistochemistry (IHC) approach. SB-334867 (20 mg/kg) increased escape latency in SB-treated rats compared to SB-vehicle group (P < 0.01). SB-treated rats spent less time in the target quadrant compared to the SB-vehicle group (P < 0.001). Distance traveled in the target quadrant was significantly more in SB-treated rats compared to the SB-vehicle group (P < 0.001). Furthermore, SB-334867 decreased PLCβ3 levels in the CA1 of the hippocampus (P < 0.01 and P < 0.05, respectively). Put together, our results suggest that the long-term inhibition of OXR1 plays a prominent role in spatial learning and memory, probably by attenuating PLCβ3 in CA1 neurons.
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14
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Alteration of Phospholipase C Expression in Rat Visual Cortical Neurons by Chronic Blockade of Orexin Receptor 1. Int J Pept Res Ther 2019. [DOI: 10.1007/s10989-019-09943-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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15
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Turku A, Leino TO, Karhu L, Yli-Kauhaluoma J, Kukkonen JP, Wallén EAA, Xhaard H. Structure-Activity Relationships of 1-Benzoylazulenes at the OX 1 and OX 2 Orexin Receptors. ChemMedChem 2019; 14:965-981. [PMID: 30892823 DOI: 10.1002/cmdc.201900074] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 03/20/2019] [Indexed: 11/08/2022]
Abstract
We previously demonstrated the potential of di- or trisubstituted azulenes as ligands (potentiators, weak agonists, and antagonists) of the orexin receptors. In this study we investigated 27 1-benzoylazulene derivatives, uncovering seven potentiators of the orexin response on OX1 and two weak dual orexin receptor agonists. For potentiators, replacement of the azulene scaffold by indole retained the activity of four out of six compounds. The structure-activity relationships for agonism and potentiation can be summarized into a bicyclic aromatic ring system substituted with two hydrogen-bond acceptors (1-position, benzoyl; 6-position, carboxyl/ester) within 7-8 Å of each other; a third acceptor at the 3-position is also well tolerated. The same pharmacophoric signature is found in the preferred conformations of the orexin receptor agonist Nag26 from molecular dynamics simulations. Subtle changes switch the activity between weak agonism and potentiation, suggesting overlapping binding sites.
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Affiliation(s)
- Ainoleena Turku
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland.,Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014, Helsinki, Finland
| | - Teppo O Leino
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
| | - Lasse Karhu
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
| | - Jari Yli-Kauhaluoma
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
| | - Jyrki P Kukkonen
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014, Helsinki, Finland.,Department of Physiology, Faculty of Medicine, University of Helsinki, P.O. Box 63, 00014, Helsinki, Finland
| | - Erik A A Wallén
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
| | - Henri Xhaard
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland
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Wang P, Wang M, Zhang L, Zhong S, Jiang W, Wang Z, Sun C, Zhang S, Liu Z. Functional characterization of an orexin neuropeptide in amphioxus reveals an ancient origin of orexin/orexin receptor system in chordate. SCIENCE CHINA-LIFE SCIENCES 2019; 62:1655-1669. [PMID: 30945108 DOI: 10.1007/s11427-018-9421-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Accepted: 10/10/2018] [Indexed: 01/09/2023]
Abstract
Amphioxus belongs to the subphylum cephalochordata, an extant representative of the most basal chordates, whose regulation of endocrine system remains ambiguous. Here we clearly demonstrated the existence of a functional orexin neuropeptide in amphioxus, which is able to interact with orexin receptor, activate both PKC and PKA pathways, decrease leptin expression, and stimulate lipogenesis. We also showed the transcription level of amphioxus orexin was affected by fasting or temperature, indicating a role of this gene in the regulation of energy balance. In addition, the expression of the amphioxus orexin was detected at cerebral vesicle, which has been proposed to be a homolog of the vertebrate brain. These data collectively suggest that a functional orexin neuropeptide has already emerged in amphioxus, which provide insights into the evolutionary origin of orexin in chordate and the functional homology between the cerebral vesicle and vertebrate brain.
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Affiliation(s)
- Peng Wang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Meng Wang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Liping Zhang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Shenjie Zhong
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Wanyue Jiang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Ziyue Wang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Chen Sun
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Shicui Zhang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China.
| | - Zhenhui Liu
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China.
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17
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Davoudi M, Azizi H, Mirnajafi-Zadeh J, Semnanian S. Decrease of inhibitory synaptic currents of locus coeruleus neurons via orexin type 1 receptors in the context of naloxone-induced morphine withdrawal. J Physiol Sci 2019; 69:281-293. [PMID: 30406600 PMCID: PMC10717061 DOI: 10.1007/s12576-018-0645-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 10/25/2018] [Indexed: 10/27/2022]
Abstract
Acute opioid withdrawal syndrome is a series of neurological symptoms caused by the abrupt cessation of the chronic administration of opioids such as morphine. The locus coeruleus (LC) in the brain stem receives a dense projection of orexinergic fibers from the hypothalamus and is a candidate site for the expression of the somatic aspects of morphine withdrawal. Previous studies have shown that orexin-A contributes to the behavioral symptoms of naloxone-induced morphine withdrawal, partly by reducing the activity of GABAergic neurons, suggesting that orexin-A may negatively modulate fast GABAergic neurotransmission during morphine withdrawal. We used whole-cell patch-clamp recordings of LC neurons in brainstem slices to investigate the effect of orexin-A on bicuculline-sensitive GABAergic inhibitory postsynaptic currents (IPSCs) during naloxone-induced morphine withdrawal. Male Wistar rats (P14-P21) were given morphine (20 mg/kg, i.p.) daily for seven consecutive days to create dependency on the drug. The application of naloxone (1 µM) to brain slices of morphine-treated rats reduced the amplitude of evoked IPSCs (eIPSCs) as well as spontaneous IPSCs (sIPSCs) frequency but did not change sIPSCs amplitude. Orexin-A (100 nM) significantly enhanced the suppressive effect of naloxone on eIPSCs amplitude and sIPSCs frequency but had no effect on the presence of the orexin type 1 receptor (OX1R) antagonist, SB-334867. Orexin-A alone had no significant effect on eIPSCs and sIPSCs in the absence of naloxone. In summary, our results show that orexin-A, via OX1R, potentiates the suppressive effect of naloxone on GABAergic IPSCs of LC neurons in morphine-treated rats. We conclude that orexins may have a critical role in regulating GABAergic neurotransmission to LC neurons during naloxone-induced morphine withdrawal.
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Affiliation(s)
- Mahnaz Davoudi
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
| | - Hossein Azizi
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
| | - Javad Mirnajafi-Zadeh
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Saeed Semnanian
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
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18
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Palus-Chramiec K, Chrobok L, Kepczynski M, Lewandowski MH. Orexin A depolarises rat intergeniculate leaflet neurons through non-selective cation channels. Eur J Neurosci 2019; 50:2683-2693. [PMID: 30803080 DOI: 10.1111/ejn.14394] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 02/12/2019] [Accepted: 02/15/2019] [Indexed: 12/22/2022]
Abstract
Orexins/hypocretins are hypothalamic neuropeptides that have a variety of functions, including maintenance of arousal, control over the sleep/wake cycle, reward and feeding. Accumulating evidence links orexins to the time-keeping system with a documented action in the master clock-the suprachiasmatic nucleus. The intergeniculate leaflet (IGL) is a thalamic structure with the well-known function of collecting photic and non-photic cues to adjust the rhythm of the suprachiasmatic nucleus to changing environmental conditions. The IGL consists of GABAergic neurons that are intrinsically active, even in slice preparations. Our previous studies revealed the excitatory postsynaptic effects of orexins on single IGL neurons, even though the ionic mechanism underlying this effect remained elusive. Therefore, in this study, we used patch clamp electrophysiology to identify the ions and distinct ion channels responsible for the observed depolarisations. The major finding of this article is that the orexin A-evoked depolarisation of IGL neurons depends on non-selective cation channels, implicating the orexinergic tone in establishing the basal firing rate in these cells. The data presented here strengthen the mutual connections between the time-keeping and orexinergic systems.
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Affiliation(s)
- Katarzyna Palus-Chramiec
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University in Krakow, Krakow, Poland
| | - Lukasz Chrobok
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University in Krakow, Krakow, Poland
| | - Mariusz Kepczynski
- Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University in Krakow, Krakow, Poland
| | - Marian Henryk Lewandowski
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University in Krakow, Krakow, Poland
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19
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Rinne MK, Leino TO, Turku A, Turunen PM, Steynen Y, Xhaard H, Wallén EA, Kukkonen JP. Pharmacological characterization of the orexin/hypocretin receptor agonist Nag 26. Eur J Pharmacol 2018; 837:137-144. [DOI: 10.1016/j.ejphar.2018.09.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 08/31/2018] [Accepted: 09/04/2018] [Indexed: 12/22/2022]
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20
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Leino TO, Turku A, Yli-Kauhaluoma J, Kukkonen JP, Xhaard H, Wallén EA. Azulene-based compounds for targeting orexin receptors. Eur J Med Chem 2018; 157:88-100. [DOI: 10.1016/j.ejmech.2018.07.040] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 06/29/2018] [Accepted: 07/15/2018] [Indexed: 01/08/2023]
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21
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Wang C, Wang Q, Ji B, Pan Y, Xu C, Cheng B, Bai B, Chen J. The Orexin/Receptor System: Molecular Mechanism and Therapeutic Potential for Neurological Diseases. Front Mol Neurosci 2018; 11:220. [PMID: 30002617 PMCID: PMC6031739 DOI: 10.3389/fnmol.2018.00220] [Citation(s) in RCA: 111] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 06/06/2018] [Indexed: 12/25/2022] Open
Abstract
Orexins, also known as hypocretins, are two neuropeptides secreted from orexin-containing neurons, mainly in the lateral hypothalamus (LH). Orexins orchestrate their effects by binding and activating two G-protein–coupled receptors (GPCRs), orexin receptor type 1 (OX1R) and type 2 (OX2R). Orexin/receptor pathways play vital regulatory roles in many physiological processes, especially feeding behavior, sleep–wake rhythm, reward and addiction and energy balance. Furthermore several reports showed that orexin/receptor pathways are involved in pathological processes of neurological diseases such as narcolepsy, depression, ischemic stroke, drug addiction and Alzheimer’s disease (AD). This review article summarizes the expression patterns, physiological functions and potential molecular mechanisms of the orexin/receptor system in neurological diseases, providing an overall framework for considering these pathways from the standpoints of basic research and clinical treatment of neurological diseases.
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Affiliation(s)
- Chunmei Wang
- Neurobiology Key Laboratory of Jining Medical University in Colleges of Shandong, Jining Medical University, Jining, China
| | - Qinqin Wang
- Neurobiology Key Laboratory of Jining Medical University in Colleges of Shandong, Jining Medical University, Jining, China
| | - Bingyuan Ji
- Neurobiology Key Laboratory of Jining Medical University in Colleges of Shandong, Jining Medical University, Jining, China
| | - Yanyou Pan
- Neurobiology Key Laboratory of Jining Medical University in Colleges of Shandong, Jining Medical University, Jining, China
| | - Chao Xu
- Neurobiology Key Laboratory of Jining Medical University in Colleges of Shandong, Jining Medical University, Jining, China
| | - Baohua Cheng
- Neurobiology Key Laboratory of Jining Medical University in Colleges of Shandong, Jining Medical University, Jining, China
| | - Bo Bai
- Neurobiology Key Laboratory of Jining Medical University in Colleges of Shandong, Jining Medical University, Jining, China
| | - Jing Chen
- Neurobiology Key Laboratory of Jining Medical University in Colleges of Shandong, Jining Medical University, Jining, China.,Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
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22
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Karhu L, Weisell J, Turunen PM, Leino TO, Pätsi H, Xhaard H, Kukkonen JP, Wallén EAA. Stapled truncated orexin peptides as orexin receptor agonists. Peptides 2018; 102:54-60. [PMID: 29475074 DOI: 10.1016/j.peptides.2018.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/29/2018] [Accepted: 02/16/2018] [Indexed: 10/18/2022]
Abstract
The peptides orexin-A and -B, the endogenous agonists of the orexin receptors, have similar 19-amino-acid C-termini which retain full maximum response as truncated peptides with only marginally reduced potency, while further N-terminal truncations successively reduce the activity. The peptides have been suggested to bind in an α-helical conformation, and truncation beyond a certain critical length is likely to disrupt the overall helical structure. In this study, we set out to stabilize the α-helical conformation of orexin-A15-33 via peptide stapling at four different sites. At a suggested hinge region, we varied the length of the cross-linker as well as replaced the staple with two α-aminoisobutyric acid residues. Modifications close to the peptide C-terminus, which is crucial for activity, were not allowed. However, central and N-terminal modifications yielded bioactive peptides, albeit with decreased potencies. This provides evidence that the orexin receptors can accommodate and be activated by α-helical peptides. The decrease in potency is likely linked to a stabilization of suboptimal peptide conformation or blocking of peptide backbone-receptor interactions at the hinge region by the helical stabilization or the modified amino acids.
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Affiliation(s)
- Lasse Karhu
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, POB 56, FI-00014 University of Helsinki, Finland.
| | - Janne Weisell
- School of Pharmacy, University of Eastern Finland, POB 1627, FI-70211 Kuopio, Finland.
| | - Pauli M Turunen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, Faculty of Veterinary Medicine, POB 66, FI-00014, University of Helsinki, Finland; Department of Physiology, Institute of Biomedicine, Biomedicum Helsinki, POB 63, FI-00014 University of Helsinki, Finland.
| | - Teppo O Leino
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, POB 56, FI-00014 University of Helsinki, Finland.
| | - Henri Pätsi
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, POB 56, FI-00014 University of Helsinki, Finland.
| | - Henri Xhaard
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, POB 56, FI-00014 University of Helsinki, Finland.
| | - Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, Faculty of Veterinary Medicine, POB 66, FI-00014, University of Helsinki, Finland; Department of Physiology, Institute of Biomedicine, Biomedicum Helsinki, POB 63, FI-00014 University of Helsinki, Finland.
| | - Erik A A Wallén
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, POB 56, FI-00014 University of Helsinki, Finland.
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23
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Coleman PJ, Gotter AL, Herring WJ, Winrow CJ, Renger JJ. The Discovery of Suvorexant, the First Orexin Receptor Drug for Insomnia. Annu Rev Pharmacol Toxicol 2017; 57:509-533. [PMID: 27860547 DOI: 10.1146/annurev-pharmtox-010716-104837] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Historically, pharmacological therapies have used mechanisms such as γ-aminobutyric acid A (GABAA) receptor potentiation to drive sleep through broad suppression of central nervous system activity. With the discovery of orexin signaling loss as the etiology underlying narcolepsy, a disorder associated with hypersomnolence, orexin antagonism emerged as an alternative approach to attenuate orexin-induced wakefulness more selectively. Dual orexin receptor antagonists (DORAs) block the activity of orexin 1 and 2 receptors to both reduce the threshold to transition into sleep and attenuate orexin-mediated arousal. Among DORAs evaluated clinically, suvorexant has pharmacokinetic properties engineered for a plasma half-life appropriate for rapid sleep onset and maintenance at low to moderate doses. Unlike GABAA receptor modulators, DORAs promote both non-rapid eye movement (NREM) and REM sleep, do not disrupt sleep stage-specific quantitative electroencephalogram spectral profiles, and allow somnolence indistinct from normal sleep. The preservation of cognitive performance and the ability to arouse to salient stimuli after DORA administration suggest further advantages over historical therapies.
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Affiliation(s)
- Paul J Coleman
- Department of Medicinal Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486;
| | - Anthony L Gotter
- Department of Neuroscience, Merck Research Laboratories, West Point, Pennsylvania 19486
| | - W Joseph Herring
- Department of Clinical Neuroscience, Merck Research Laboratories, West Point, Pennsylvania 19486
| | - Christopher J Winrow
- Department of Neuroscience, Merck Research Laboratories, West Point, Pennsylvania 19486
| | - John J Renger
- Department of Neuroscience, Merck Research Laboratories, West Point, Pennsylvania 19486
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24
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Abstract
Orexin/hypocretin peptide (orexin-A and orexin-B) signaling is believed to take place via the two G-protein-coupled receptors (GPCRs), named OX1 and OX2 orexin receptors, as described in the previous chapters. Signaling of orexin peptides has been investigated in diverse endogenously orexin receptor-expressing cells - mainly neurons but also other types of cells - and in recombinant cells expressing the receptors in a heterologous manner. Findings in the different systems are partially convergent but also indicate cellular background-specific signaling. The general picture suggests an inherently high degree of diversity in orexin receptor signaling.In the current chapter, I present orexin signaling on the cellular and molecular levels. Discussion of the connection to (potential) physiological orexin responses is only brief since these are in focus of other chapters in this book. The same goes for the post-synaptic signaling mechanisms, which are dealt with in Burdakov: Postsynaptic actions of orexin. The current chapter is organized according to the tissue type, starting from the central nervous system. Finally, receptor signaling pathways are discussed across tissues, cell types, and even species.
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Affiliation(s)
- Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, POB 66, FIN-00014, Helsinki, Finland.
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25
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Antagonism of orexin type-1 receptors (OX1Rs) attenuates naloxone-precipitated morphine withdrawal syndrome in rat dorsal hippocampus. Pharmacol Biochem Behav 2017; 158:39-48. [DOI: 10.1016/j.pbb.2017.06.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Revised: 05/09/2017] [Accepted: 06/01/2017] [Indexed: 11/22/2022]
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26
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Turku A, Rinne MK, Boije af Gennäs G, Xhaard H, Lindholm D, Kukkonen JP. Orexin receptor agonist Yan 7874 is a weak agonist of orexin/hypocretin receptors and shows orexin receptor-independent cytotoxicity. PLoS One 2017; 12:e0178526. [PMID: 28575023 PMCID: PMC5456073 DOI: 10.1371/journal.pone.0178526] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 05/15/2017] [Indexed: 01/22/2023] Open
Abstract
Two promising lead structures of small molecular orexin receptor agonist have been reported, but without detailed analyses of the pharmacological properties. One of them, 1-(3,4-dichlorophenyl)-2-[2-imino-3-(4-methylbenzyl)-2,3-dihydro-1H-benzo[d]imidazol-1-yl]ethan-1-ol (Yan 7874), is commercially available, and we set out to analyze its properties. As test system we utilized human OX1 and OX2 orexin receptor-expressing Chinese hamster ovary (CHO) K1 cells as well as control CHO-K1 and neuro-2a neuroblastoma cells. Gq-coupling was assessed by measurement of intracellular Ca2+ and phospholipase C activity, and the coupling to Gi and Gs by adenylyl cyclase inhibition and stimulation, respectively. At concentrations above 1 μM, strong Ca2+ and low phospholipase C responses to Yan 7874 were observed in both OX1- and OX2-expressing cells. However, a major fraction of the response was not mediated by orexin receptors, as determined utilizing the non-selective orexin receptor antagonist N-biphenyl-2-yl-1-{[(1-methyl-1H-benzimidazol-2-yl)sulfanyl]acetyl}-L-prolinamide (TCS 1102) as well as control CHO-K1 cells. Yan 7874 did not produce any specific adenylyl cyclase response. Some experiments suggested an effect on cell viability by Yan 7874, and we thus analyzed this. Within a few hours of exposure, Yan 7874 markedly changed cell morphology (shrunken, rich in vacuoles), reduced growth, promoted cell detachment, and induced necrotic cell death. The effect was equal in cells expressing orexin receptors or not. Thus, Yan 7874 is a weak partial agonist of orexin receptors. It also displays strong off-target effects in the same concentration range, culminating in necrotic cell demise. This makes Yan 7874 unsuitable as orexin receptor agonist.
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Affiliation(s)
- Ainoleena Turku
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Maiju K. Rinne
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Gustav Boije af Gennäs
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Henri Xhaard
- Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Dan Lindholm
- Department of Biochemistry and Developmental Biology, Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Jyrki P. Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
- * E-mail:
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27
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Immunoprofiling of Adult-Derived Human Liver Stem/Progenitor Cells: Impact of Hepatogenic Differentiation and Inflammation. Stem Cells Int 2017; 2017:2679518. [PMID: 28491094 PMCID: PMC5405586 DOI: 10.1155/2017/2679518] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 02/15/2017] [Accepted: 03/02/2017] [Indexed: 02/08/2023] Open
Abstract
Adult-derived human liver stem/progenitor cells (ADHLSCs) are, nowadays, developed as therapeutic medicinal product for the treatment of liver defects. In this study, the impact of hepatogenic differentiation and inflammation priming on the ADHLSCs' immune profile was assessed in vitro and compared to that of mature hepatocytes. The constitutive immunological profile of ADHLSCs was greatly different from that of hepatocytes. Differences in the expression of the stromal markers CD90 and CD105, adhesion molecules CD44 and CD49e, immunoregulatory molecules CD73 and HO-1, and NK ligands CD112 and CD155 were noted. While they globally preserved their immunological profile in comparison to undifferentiated counterparts, differentiated ADHLSCs showed a significant downregulation of CD200 expression as in hepatocytes. This was mainly induced by signals issued from EGF and OSM. On the other hand, the impact of inflammation was quite similar for all studied cell populations with an increased expression level of CD54 and CD106 and induction of that of CD40 and CD274. In conclusion, our immune profiling study suggests CD200 as a key factor in regulating the immunobiology of differentiated ADHLSCs. A better understanding of the molecular and physiological events related to such marker could help in designing the optimal conditions for an efficient therapeutic use of ADHLSCs.
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Pasban-Aliabadi H, Esmaeili-Mahani S, Abbasnejad M. Orexin-A Protects Human Neuroblastoma SH-SY5Y Cells Against 6-Hydroxydopamine-Induced Neurotoxicity: Involvement of PKC and PI3K Signaling Pathways. Rejuvenation Res 2017; 20:125-133. [PMID: 27814668 DOI: 10.1089/rej.2016.1836] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Parkinson's disease (PD) is a common neurodegenerative disorder that is characterized by progressive and selective death of dopaminergic neurons. Multifunctional neuropeptide orexin-A is involved in many biological events of the body. It has been shown that orexin-A has protective effects in neurodegenerative disease such as PD. However, its cellular mechanisms have not yet been fully clarified. Here, we investigated the intracellular signaling pathway of orexin-A neuroprotection in 6-hydroxydopamine (6-OHDA)-induced SH-SY5H cells damage as an in vitro model of PD. The cells were incubated with 150 μM 6-OHDA, and the viability was examined by 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2-tetrazolium bromide (MTT) assay. Mitochondrial membrane potential and intracellular calcium were measured by fluorescent probes. Western blotting was also used to determine cyclooxygenase type 2 (COX-2), nuclear factor erythroid 2 related factor 2 (Nrf2), and HSP70 protein levels. The data showed that 6-OHDA has decreasing effects on cell viability, Nrf2, and HSP70 protein expression and increases the level of mitochondrial membrane potential, intracellular calcium, and COX-2 protein. Orexin-A (500 pM) significantly attenuated the 6-OHDA-induced cell damage. Furthermore, Orexin-A significantly prevented the mentioned effects of 6-OHDA on SH-SY5Y cells. Orexin 1 receptor antagonist (SB3344867), PKC, and PI3-kinase (PI3K) inhibitors (chelerythrin and LY294002, respectively) could suppress the orexin-A neuroprotective effect. In contrast, blockage of PKA by a selective inhibitor (KT5720) had no effects on the orexin protection. The results suggest that orexin-A protective effects against 6-OHDA-induced neurotoxicity are performed via its receptors, PKC and PI3K signaling pathways.
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Affiliation(s)
- Hamzeh Pasban-Aliabadi
- 1 Department of Biology, Faculty of Sciences, ShahidBahonar University of Kerman , Kerman, Iran
| | - Saeed Esmaeili-Mahani
- 1 Department of Biology, Faculty of Sciences, ShahidBahonar University of Kerman , Kerman, Iran .,2 Laboratory of Molecular Neuroscience, Kerman Neuroscience Research Center (KNRC), Kerman University of Medical Sciences , Kerman, Iran
| | - Mehdi Abbasnejad
- 1 Department of Biology, Faculty of Sciences, ShahidBahonar University of Kerman , Kerman, Iran
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Wallace DJ, Mangion I, Coleman P. Discovery and Chemical Development of Suvorexant - A Dual Orexin Antagonist for Sleep Disorder. ACTA ACUST UNITED AC 2016. [DOI: 10.1021/bk-2016-1239.ch001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Affiliation(s)
- Debra J. Wallace
- Department of Process Chemistry, Merck and Co, Rahway, New Jersey, 07065, United States
- Department of Medicinal Chemistry, Merck and Co, Westpoint, Pennsylvania, 19486, United States
| | - Ian Mangion
- Department of Process Chemistry, Merck and Co, Rahway, New Jersey, 07065, United States
- Department of Medicinal Chemistry, Merck and Co, Westpoint, Pennsylvania, 19486, United States
| | - Paul Coleman
- Department of Process Chemistry, Merck and Co, Rahway, New Jersey, 07065, United States
- Department of Medicinal Chemistry, Merck and Co, Westpoint, Pennsylvania, 19486, United States
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Chen XY, Chen L, Du YF. Orexin-A increases the firing activity of hippocampal CA1 neurons through orexin-1 receptors. J Neurosci Res 2016; 95:1415-1426. [PMID: 27796054 DOI: 10.1002/jnr.23975] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 09/29/2016] [Accepted: 10/04/2016] [Indexed: 12/15/2022]
Affiliation(s)
- Xin-Yi Chen
- Department of Neurology; Provincial Hospital Affiliated to Shandong University; Jinan Shandong China
| | - Lei Chen
- Department of Physiology; Qingdao University; Qingdao China
| | - Yi-Feng Du
- Department of Neurology; Provincial Hospital Affiliated to Shandong University; Jinan Shandong China
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31
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Turku A, Borrel A, Leino TO, Karhu L, Kukkonen JP, Xhaard H. Pharmacophore Model To Discover OX1 and OX2 Orexin Receptor Ligands. J Med Chem 2016; 59:8263-75. [DOI: 10.1021/acs.jmedchem.6b00333] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Ainoleena Turku
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
- Faculty of Veterinary Medicine, Department of Veterinary Biosciences, University of Helsinki, P.O. Box 66, FIN-00014 Helsinki, Finland
| | - Alexandre Borrel
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
| | - Teppo O. Leino
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
| | - Lasse Karhu
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
| | - Jyrki P. Kukkonen
- Faculty of Veterinary Medicine, Department of Veterinary Biosciences, University of Helsinki, P.O. Box 66, FIN-00014 Helsinki, Finland
| | - Henri Xhaard
- Faculty of Pharmacy,
Division of Pharmaceutical Chemistry and Technology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland
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Imperatore R, Palomba L, Morello G, Spiezio AD, Piscitelli F, Marzo VD, Cristino L. Formation of OX-1R/CB 1 R heteromeric complexes in embryonic mouse hypothalamic cells: Effect on intracellular calcium, 2-arachidonoyl-glycerol biosynthesis and ERK phosphorylation. Pharmacol Res 2016; 111:600-609. [DOI: 10.1016/j.phrs.2016.07.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 06/27/2016] [Accepted: 07/06/2016] [Indexed: 12/16/2022]
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Kukkonen JP. G-protein-dependency of orexin/hypocretin receptor signalling in recombinant Chinese hamster ovary cells. Biochem Biophys Res Commun 2016; 476:379-385. [PMID: 27237973 DOI: 10.1016/j.bbrc.2016.05.130] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 05/25/2016] [Indexed: 01/07/2023]
Abstract
Multiple signalling pathways for orexin receptors have been discovered, and most thoroughly mapped in Chinese hamster ovary K1 (CHO-K1) cells. It is also known that orexin receptors can couple to the G-protein families Gi, Gs and Gq. However, the connection between the G-proteins and the downstream signals is only vaguely established, and we now set out to resolve this for human orexin receptors expressed in CHO-K1 cells. Adenylyl cyclase (AC), phospholipase A2, C and D, and diacylglycerol lipase activities were assessed by precursor radiolabelling and chromatographic separation, and calcium by fluorescent methods. Pertussis toxin, cholera toxin and the cyclic depsipeptide, UBO-QIC a.k.a. FR900359, were used to assess the involvement of Gi-, Gs- and Gq-family G-proteins, respectively. Calcium elevations as well as activation of the phospholipases and diacylglycerol lipase were dependent on Gq, as they were fully blocked by UBO-QIC. The low-potency AC activation fully depended on Gs. Surprisingly, the assumed Gi-dependent inhibition of AC was (fully or partially) inhibited by UBO-QIC, in opposition to the previous findings of no sensitivity of Gi proteins to UBO-QIC. Orexin receptor signalling is indeed mostly Gq-driven in CHO-K1 cells, even with respect to the less clearly mapped cascades such as phospholipase A2 and C and calcium influx, underlining the importance of Gq even under physiological conditions. AC regulation warrants more studies.
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Affiliation(s)
- Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, POB 66, FIN-00014, University of Helsinki, Helsinki, Finland.
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Lu GL, Lee CH, Chiou LC. Orexin A induces bidirectional modulation of synaptic plasticity: Inhibiting long-term potentiation and preventing depotentiation. Neuropharmacology 2016; 107:168-180. [PMID: 26965217 DOI: 10.1016/j.neuropharm.2016.03.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 02/19/2016] [Accepted: 03/01/2016] [Indexed: 01/30/2023]
Abstract
The orexin system consists of two peptides, orexin A and B and two receptors, OX1R and OX2R. It is implicated in learning and memory regulation while controversy remains on its role in modulating hippocampal synaptic plasticity in vivo and in vitro. Here, we investigated effects of orexin A on two forms of synaptic plasticity, long-term potentiation (LTP) and depotentiation of field excitatory postsynaptic potentials (fEPSPs), at the Schaffer Collateral-CA1 synapse of mouse hippocampal slices. Orexin A (≧30 nM) attenuated LTP induced by theta burst stimulation (TBS) in a manner antagonized by an OX1R (SB-334867), but not OX2R (EMPA), antagonist. Conversely, at 1 pM, co-application of orexin A prevented the induction of depotentiation induced by low frequency stimulation (LFS), i.e. restoring LTP. This re-potentiation effect of sub-nanomolar orexin A occurred at LFS of 1 Hz, but not 2 Hz, and with LTP induced by either TBS or tetanic stimulation. It was significantly antagonized by SB-334867, EMPA and TCS-1102, selective OX1R, OX2R and dual OXR antagonists, respectively, and prevented by D609, SQ22536 and H89, inhibitors of phospholipase C (PLC), adenylyl cyclase (AC) and protein kinase A (PKA), respectively. LFS-induced depotentiation was antagonized by blockers of NMDA, A1-adenosine and type 1/5 metabotropic glutamate (mGlu1/5) receptors, respectively. However, orexin A (1 pM) did not affect chemical-induced depotentiation by agonists of these receptors. These results suggest that orexin A bidirectionally modulates hippocampal CA1 synaptic plasticity, inhibiting LTP via OX1Rs at moderate concentrations while inducing re-potentiation via OX1Rs and OX2Rs, possibly through PLC and AC-PKA signaling at sub-nanomolar concentrations.
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Affiliation(s)
- Guan-Ling Lu
- Graduate Institute and College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chia-Hsu Lee
- Graduate Institute and College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Lih-Chu Chiou
- Graduate Institute and College of Medicine, National Taiwan University, Taipei, Taiwan; Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan; Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan; Reserach Center for Chinese Medicine & Acupuncture, China Medical University, Taichung, Taiwan.
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35
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OX2 orexin/hypocretin receptor signal transduction in recombinant Chinese hamster ovary cells. Cell Signal 2015; 28:51-60. [PMID: 26582739 DOI: 10.1016/j.cellsig.2015.11.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/30/2015] [Accepted: 11/10/2015] [Indexed: 01/06/2023]
Abstract
There are two subtypes of orexin receptors, OX1 and OX2. Signalling pathways have been mapped in much higher detail for OX1 receptors than OX2 receptors. Almost all the detailed studies have been performed in Chinese hamster ovary cells, and we thus chose the same cell background for the studies on human OX2 receptors to allow comparison to human OX1 receptors. Adenylyl cyclase, phospholipase A2, C and D and diacylglycerol lipase activities were assessed by precursor radiolabelling and chromatographic separation (ion exchange, affinity or thin layer), calcium by a fluorescent method, and receptor binding with [(125)I]-orexin-A. Upon activation with orexin-A, OX2 receptors stimulated phospholipase A2, C and D, diacylglycerol lipase and calcium elevation, and both inhibited and stimulated adenylyl cyclase; i.e., the responses to OX2 activation by orexin-A were principally like those of OX1, in contrast to some previous suggestions. The responses occurred mostly in the same concentration range as those for OX1 activation and via the same signal cascades. However, some responses were weaker, suggesting a partially differential coupling to some cascades. In summary, OX2 receptor signalling is principally similar to OX1 receptor signalling suggesting also a physiologically similar coupling, though this needs to be verified in physiological contexts. Some (relatively weak) differences between the receptors may be investigated in further studies.
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36
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Song J, Kim E, Kim CH, Song HT, Lee JE. The role of orexin in post-stroke inflammation, cognitive decline, and depression. Mol Brain 2015; 8:16. [PMID: 25884812 PMCID: PMC4357085 DOI: 10.1186/s13041-015-0106-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 02/23/2015] [Indexed: 01/02/2023] Open
Abstract
Ischemic stroke results in diverse pathophysiologies, including cerebral inflammation, neuronal loss, cognitive dysfunction, and depression. Studies aimed at identifying therapeutic solutions to alleviate these outcomes are important due to the increase in the number of stroke patients annually. Recently, many studies have reported that orexin, commonly known as a neuropeptide regulator of sleep/wakefulness and appetite, is associated with neuronal cell apoptosis, memory function, and depressive symptoms. Here, we briefly summarize recent studies regarding the role and future perspectives of orexin in post-ischemic stroke. This review advances our understanding of the role of orexin in post-stroke pathologies, focusing on its possible function as a therapeutic regulator in the post-ischemic brain. Ultimately, we suggest the clinical potential of orexin to regulate post-stroke pathologies.
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Affiliation(s)
- Juhyun Song
- Department of Anatomy, Yonsei University College of Medicine, Seoul, 120-752, South Korea.
| | - Eosu Kim
- Department of Pharmacology, Yonsei University College of Medicine, 120-752, Seoul, South Korea.
| | - Chul-Hoon Kim
- Department of Psychiatry, Yonsei University College of Medicine, 120-752, Seoul, South Korea.
| | - Ho-Taek Song
- Department of Diagnostic Radiology, Yonsei University College of Medicine, 120-752, Seoul, South Korea.
| | - Jong Eun Lee
- Department of Anatomy, Yonsei University College of Medicine, Seoul, 120-752, South Korea. .,BK21 Plus Project for Medical Sciences, and Brain Research Institute, Yonsei University, College of Medicine, Seoul, 120-752, South Korea.
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37
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Wang Z, Liu S, Kakizaki M, Hirose Y, Ishikawa Y, Funato H, Yanagisawa M, Yu Y, Liu Q. Orexin/hypocretin activates mTOR complex 1 (mTORC1) via an Erk/Akt-independent and calcium-stimulated lysosome v-ATPase pathway. J Biol Chem 2014; 289:31950-31959. [PMID: 25278019 PMCID: PMC4231673 DOI: 10.1074/jbc.m114.600015] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/30/2014] [Indexed: 02/05/2023] Open
Abstract
The lack of the neuropeptide orexin, also known as hypocretin, results in narcolepsy, a chronic sleep disorder characterized by frequent sleep/cataplexy attacks and rapid eye movement sleep abnormalities. However, the downstream pathways of orexin signaling are not clearly understood. Here, we show that orexin activates the mTOR pathway, a central regulator of cell growth and metabolism, in the mouse brain and multiple recombinant cell lines that express the G protein-coupled receptors (GPCRs), orexin 1 receptor (OX1R) or orexin 2 receptor (OX2R). This orexin/GPCR-stimulated mTOR activation is sensitive to rapamycin, an inhibitor of mTOR complex 1 (mTORC1) but is independent of two well known mTORC1 activators, Erk and Akt. Rather, our studies indicate that orexin activates mTORC1 via extracellular calcium influx and the lysosome pathway involving v-ATPase and Rag GTPases. Moreover, a cytoplasmic calcium transient is sufficient to mimic orexin/GPCR signaling to mTORC1 activation in a v-ATPase-dependent manner. Together, our studies suggest that the mTORC1 pathway functions downstream of orexin/GPCR signaling, which plays a crucial role in many physiological and metabolic processes.
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Affiliation(s)
- Zhiqiang Wang
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Shimeng Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390,; College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Miyo Kakizaki
- International Institute of Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Ibaraki 305-8575, Japan, and
| | - Yuuki Hirose
- International Institute of Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Ibaraki 305-8575, Japan, and
| | - Yukiko Ishikawa
- International Institute of Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Ibaraki 305-8575, Japan, and
| | - Hiromasa Funato
- International Institute of Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Ibaraki 305-8575, Japan, and; Department of Anatomy, Toho University School of Medicine, Tokyo 143-8540, Japan
| | - Masashi Yanagisawa
- International Institute of Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Ibaraki 305-8575, Japan, and
| | - Yonghao Yu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390,.
| | - Qinghua Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390,; International Institute of Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Ibaraki 305-8575, Japan, and.
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Putula J, Pihlajamaa T, Kukkonen JP. Calcium affects OX1 orexin (hypocretin) receptor responses by modifying both orexin binding and the signal transduction machinery. Br J Pharmacol 2014; 171:5816-28. [PMID: 25132134 DOI: 10.1111/bph.12883] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 08/05/2014] [Accepted: 08/12/2014] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND AND PURPOSE One of the major responses upon orexin receptor activation is Ca(2+) influx, and this influx seems to amplify the other responses mediated by orexin receptors. However, the reduction in Ca(2+) , often used to assess the importance of Ca(2+) influx, might affect other properties, like ligand-receptor interactions, as suggested for some GPCR systems. Hence, we investigated the role of the ligand-receptor interaction and Ca(2+) signal cascades in the apparent Ca(2+) requirement of orexin-A signalling. EXPERIMENTAL APPROACH Receptor binding was assessed in CHO cells expressing human OX1 receptors with [(125) I]-orexin-A by conventional ligand binding as well as scintillation proximity assays. PLC activity was determined by chromatography. KEY RESULTS Both orexin receptor binding and PLC activation were strongly dependent on the extracellular Ca(2+) concentration. The relationship between Ca(2+) concentration and receptor binding was the same as that for PLC activation. However, when Ca(2+) entry was reduced by depolarizing the cells or by inhibiting the receptor-operated Ca(2+) channels, orexin-A-stimulated PLC activity was much more strongly inhibited than orexin-A binding. CONCLUSIONS AND IMPLICATIONS Ca(2+) plays a dual role in orexin signalling by being a prerequisite for both ligand-receptor interaction and amplifying orexin signals via Ca(2+) influx. Some previous results obtained utilizing Ca(2+) chelators have to be re-evaluated based on the results of the current study. From a drug discovery perspective, further experiments need to identify the target for Ca(2+) in orexin-A-OX1 receptor interaction and its mechanism of action.
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Affiliation(s)
- Jaana Putula
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
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Kukkonen JP, Leonard CS. Orexin/hypocretin receptor signalling cascades. Br J Pharmacol 2014; 171:314-31. [PMID: 23902572 DOI: 10.1111/bph.12324] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 07/18/2013] [Accepted: 07/28/2013] [Indexed: 12/16/2022] Open
Abstract
Orexin (hypocretin) peptides and their two known G-protein-coupled receptors play essential roles in sleep-wake control and powerfully influence other systems regulating appetite/metabolism, stress and reward. Consequently, drugs that influence signalling by these receptors may provide novel therapeutic opportunities for treating sleep disorders, obesity and addiction. It is therefore critical to understand how these receptors operate, the nature of the signalling cascades they engage and their physiological targets. In this review, we evaluate what is currently known about orexin receptor signalling cascades, while a sister review (Leonard & Kukkonen, this issue) focuses on tissue-specific responses. The evidence suggests that orexin receptor signalling is multifaceted and is substantially more diverse than originally thought. Indeed, orexin receptors are able to couple to members of at least three G-protein families and possibly other proteins, through which they regulate non-selective cation channels, phospholipases, adenylyl cyclase, and protein and lipid kinases. In the central nervous system, orexin receptors produce neuroexcitation by postsynaptic depolarization via activation of non-selective cation channels, inhibition of K⁺ channels and activation of Na⁺/Ca²⁺ exchange, but they also can stimulate the release of neurotransmitters by presynaptic actions and modulate synaptic plasticity. Ca²⁺ signalling is also prominently influenced by these receptors, both via the classical phospholipase C-Ca²⁺ release pathway and via Ca²⁺ influx, mediated by several pathways. Upon longer-lasting stimulation, plastic effects are observed in some cell types, while others, especially cancer cells, are stimulated to die. Thus, orexin receptor signals appear highly tunable, depending on the milieu in which they are operating.
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Affiliation(s)
- J P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
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Abstract
Addiction is a chronic relapsing disorder which presents a significant global health burden and unmet medical need. The orexin/hypocretin system is an attractive potential therapeutic target as demonstrated by the successful clinical trials of antagonist medications like Suvorexant for insomnia. It is composed of two neuropeptides, orexin-A and orexin-B and two excitatory and promiscuous G-protein coupled receptors, OX1 and OX2. Orexins are known to have a variety of functions, most notably in regulating arousal, appetite and reward. The orexins have been shown to have a role in mediating the effects of several drugs of abuse, such as cocaine, morphine and alcohol via projections to key brain regions such as the ventral tegmental area, nucleus accumbens and prefrontal cortex. However, it has not yet been demonstrated whether the dual orexin receptor antagonists (DORAs) under development for insomnia are ideal drugs for the treatment of addiction. The question of whether to use a DORA or single orexin receptor antagonist (SORA) for the treatment of addiction is a key question that will need to be answered in order to maximize the clinical utility of orexin receptor antagonists. This review will examine the role of the orexin/hypocretin system in addiction, orexin-based pharmacotherapies under development and factors affecting the selection of one or both orexin receptors as drug targets for the treatment of addiction.
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Chen Q, de Lecea L, Hu Z, Gao D. The hypocretin/orexin system: an increasingly important role in neuropsychiatry. Med Res Rev 2014; 35:152-97. [PMID: 25044006 DOI: 10.1002/med.21326] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Hypocretins, also named as orexins, are excitatory neuropeptides secreted by neurons specifically located in lateral hypothalamus and perifornical areas. Orexinergic fibers are extensively distributed in various brain regions and involved in a number of physiological functions, such as arousal, cognition, stress, appetite, and metabolism. Arousal is the most important function of orexin system as dysfunction of orexin signaling leads to narcolepsy. In addition to narcolepsy, orexin dysfunction is associated with serious neural disorders, including addiction, depression, and anxiety. However, some results linking orexin with these disorders are still contradictory, which may result from differences of detection methods or the precision of tools used in measurements; strategies targeted to orexin system (e.g., antagonists to orexin receptors, gene delivery, and cell transplantation) are promising new tools for treatment of neuropsychiatric disorders, though studies are still in a stage of preclinical or clinical research.
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Affiliation(s)
- Quanhui Chen
- Department of Physiology, Third Military Medical University, Chongqing 400038, China; Department of Sleep and Psychology, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400038, China
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Heterodimerization of mouse orexin type 2 receptor variants and the effects on signal transduction. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:652-63. [PMID: 24368186 DOI: 10.1016/j.bbamcr.2013.12.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 12/09/2013] [Accepted: 12/13/2013] [Indexed: 02/03/2023]
Abstract
Orexin-A and Orexin-B play important roles in many physiological processes in which Orexins orchestrate diverse downstream effects via two G-protein coupled receptors: Orexin1R and Orexin2R. Two alternative C-terminus splice variants of the mouse Orexin receptors mOX2alphaR and mOX2betaR have recently been identified. This study explored the possibility of heterodimerization between mOX2alphaR and mOX2betaR, and investigated novel signal transduction characteristics after stimulation. The dimerization of mOX2alphaR and mOX2betaR was confirmed by BRET and co-immunoprecipitation assays. Meanwhile, in HEK293 cells, co-expression of mOX2alphaR and mOX2betaR resulted in a strengthened increase in activation of ERK1/2, with maximal activation at 5 min and 100 nM. Furthermore, heterodimerization also elicits stronger intracellular Ca2+ elevation after Orexin(s) stimulation, followed by a slower decline in intracellular Ca2+ to a steady endpoint Protein Kinase C Inhibitor significantly inhibited these downstream effects. In addition, the cAMP response element reporter activities were significantly reduced, whereas the serum response element luciferase and the T-lymphocyte activation of nuclear factor-responsive element reporter activity were significantly up-regulated after Orexin(s) stimulation. Besides, Orexin-A/-B induced a significantly higher rate of HEK293 cell proliferation in cells co-expressing mOX2alphaR/mOX2betaR compared to the control group. Taken together, we provide conclusive evidence that mOX2alphaR can form a functional heterodimer with mOX2betaR and this leads to increased PKC and decreased protein kinase A activity by ERK signal pathway leading to a significant increase in cell proliferation. The nature of this signaling pathway has significant implications for the role of Orexin in the regulation of physiological processes including the homeostasis of feeding.
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43
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Merlo Pich E, Melotto S. Orexin 1 receptor antagonists in compulsive behavior and anxiety: possible therapeutic use. Front Neurosci 2014; 8:26. [PMID: 24592206 PMCID: PMC3923148 DOI: 10.3389/fnins.2014.00026] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 01/27/2014] [Indexed: 11/16/2022] Open
Abstract
Fifteen years after the discovery of hypocretin/orexin a large body of evidence has been collected supporting its critical role in the modulation of several regulatory physiological functions. While reduced levels of hypocretin/orexin were initially associated with narcolepsy, increased levels have been linked in recent years to pathological states of hypervigilance and, in particular, to insomnia. The filing to FDA of the dual-activity orexin receptor antagonist (DORA) suvorexant for the indication of insomnia further corroborates the robustness of such evidences. However, as excessive vigilance is also typical of anxiety and panic episodes, as well as of abstinence and craving in substance misuse disorders. In this review we briefly discuss the evidence supporting the development of hypocretin/orexin receptor 1 (OX1) antagonists for these indications. Experiments using the OX1 antagonist SB-334867 and mutant mice have involved the OX1 receptor in mediating the compulsive reinstatement of drug seeking for ethanol, nicotine, cocaine, cannabinoids and morphine. More recently, data have been generated with the novel selective OX1 antagonists GSK1059865 and ACT-335827 on behavioral and cardiovascular response to stressors and panic-inducing agents in animals. Concluding, while waiting for pharmacologic data to become available in humans, risks and benefits for the development of an OX1 receptor antagonist for Binge Eating and Anxiety Disorders are discussed.
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44
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Zawilska JB, Urbańska A, Sokołowska P. Orexins/hypocretins stimulate accumulation of inositol phosphate in primary cultures of rat cortical neurons. Pharmacol Rep 2014; 65:513-6. [PMID: 23744436 DOI: 10.1016/s1734-1140(13)71027-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 01/31/2012] [Indexed: 10/25/2022]
Abstract
BACKGROUND Orexins A and B (also named hypocretins 1 and 2) are hypothalamic peptides with pleiotropic activity. They signal through two G protein-coupled receptors: OX1R and OX2R. We have previously demonstrated that both types of orexin receptors are expressed in cultured rat cortical neurons, and stimulation of the predominant OX2R inhibits cyclic AMP synthesis. In the present work, we examined effects of orexins on inositol phosphate (IP) accumulation in rat cortical neurons. METHODS Experiments were performed on primary neuronal cell cultures prepared from Wistar rat embryos on day 17 of gestation. Following 1 h incubation with orexins, IP levels were measured using the ELISA IP-One assay kit. RESULTS Orexins A and B increased, in a concentration-dependent manner, IP accumulation in primary neuronal cell cultures from rat cerebral cortex. Both peptides acted with a similar potency. The calculated EC50 values were 6.0 nM and 10.4 nM for orexin A and orexin B, respectively. CONCLUSION The results indicate that in cultured rat cortical neurons orexin receptors are also coupled to inositol phosphates signaling pathway.
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Affiliation(s)
- Jolanta B Zawilska
- Institute for Medical Biology, Polish Academy of Sciences, Lodowa 106, PL 93-232 Łódź, Poland.
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45
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Leonard CS, Kukkonen JP. Orexin/hypocretin receptor signalling: a functional perspective. Br J Pharmacol 2014; 171:294-313. [PMID: 23848055 PMCID: PMC3904253 DOI: 10.1111/bph.12296] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 06/17/2013] [Accepted: 07/03/2013] [Indexed: 10/26/2022] Open
Abstract
Multiple homeostatic systems are regulated by orexin (hypocretin) peptides and their two known GPCRs. Activation of orexin receptors promotes waking and is essential for expression of normal sleep and waking behaviour, with the sleep disorder narcolepsy resulting from the absence of orexin signalling. Orexin receptors also influence systems regulating appetite/metabolism, stress and reward, and are found in several peripheral tissues. Nevertheless, much remains unknown about the signalling pathways and targets engaged by native receptors. In this review, we integrate knowledge about the orexin receptor signalling capabilities obtained from studies in expression systems and various native cell types (as presented in Kukkonen and Leonard, this issue of British Journal of Pharmacology) with knowledge of orexin signalling in different tissues. The tissues reviewed include the CNS, the gastrointestinal tract, the pituitary gland, pancreas, adrenal gland, adipose tissue and the male reproductive system. We also summarize the findings in different native and recombinant cell lines, especially focusing on the different cascades in CHO cells, which is the most investigated cell line. This reveals that while a substantial gap exists between what is known about orexin receptor signalling and effectors in recombinant systems and native systems, mounting evidence suggests that orexin receptor signalling is more diverse than originally thought. Moreover, rather than being restricted to orexin receptor 'overexpressing' cells, this signalling diversity may be utilized by native receptors in a site-specific manner.
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Affiliation(s)
- C S Leonard
- Department of Physiology, New York Medical College, Valhalla, NY, USA
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46
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Kohlmeier KA, Tyler CJ, Kalogiannis M, Ishibashi M, Kristensen MP, Gumenchuk I, Chemelli RM, Kisanuki YY, Yanagisawa M, Leonard CS. Differential actions of orexin receptors in brainstem cholinergic and monoaminergic neurons revealed by receptor knockouts: implications for orexinergic signaling in arousal and narcolepsy. Front Neurosci 2013; 7:246. [PMID: 24391530 PMCID: PMC3869224 DOI: 10.3389/fnins.2013.00246] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 11/29/2013] [Indexed: 12/14/2022] Open
Abstract
Orexin neuropeptides influence multiple homeostatic functions and play an essential role in the expression of normal sleep-wake behavior. While their two known receptors (OX1 and OX2) are targets for novel pharmacotherapeutics, the actions mediated by each receptor remain largely unexplored. Using brain slices from mice constitutively lacking either receptor, we used whole-cell and Ca2+ imaging methods to delineate the cellular actions of each receptor within cholinergic [laterodorsal tegmental nucleus (LDT)] and monoaminergic [dorsal raphe (DR) and locus coeruleus (LC)] brainstem nuclei—where orexins promote arousal and suppress REM sleep. In slices from OX−/−2 mice, orexin-A (300 nM) elicited wild-type responses in LDT, DR, and LC neurons consisting of a depolarizing current and augmented voltage-dependent Ca2+ transients. In slices from OX−/−1 mice, the depolarizing current was absent in LDT and LC neurons and was attenuated in DR neurons, although Ca2+-transients were still augmented. Since orexin-A produced neither of these actions in slices lacking both receptors, our findings suggest that orexin-mediated depolarization is mediated by both receptors in DR, but is exclusively mediated by OX1 in LDT and LC neurons, even though OX2 is present and OX2 mRNA appears elevated in brainstems from OX−/−1 mice. Considering published behavioral data, these findings support a model in which orexin-mediated excitation of mesopontine cholinergic and monoaminergic neurons contributes little to stabilizing spontaneous waking and sleep bouts, but functions in context-dependent arousal and helps restrict muscle atonia to REM sleep. The augmented Ca2+ transients produced by both receptors appeared mediated by influx via L-type Ca2+ channels, which is often linked to transcriptional signaling. This could provide an adaptive signal to compensate for receptor loss or prolonged antagonism and may contribute to the reduced severity of narcolepsy in single receptor knockout mice.
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Affiliation(s)
- Kristi A Kohlmeier
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen Copenhagen, Denmark
| | | | - Mike Kalogiannis
- Department of Physiology, New York Medical College Valhalla, NY, USA
| | - Masaru Ishibashi
- Department of Physiology, New York Medical College Valhalla, NY, USA
| | - Morten P Kristensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen Copenhagen, Denmark
| | - Iryna Gumenchuk
- Department of Physiology, New York Medical College Valhalla, NY, USA
| | - Richard M Chemelli
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center Dallas, TX, USA
| | - Yaz Y Kisanuki
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center Dallas, TX, USA
| | - Masashi Yanagisawa
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center Dallas, TX, USA
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47
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Abstract
Obesity has increased in prevalence worldwide, attributed in part to the influences of an obesity-promoting environment and genetic factors. While obesity and overweight increasingly seem to be the norm, there remain individuals who resist obesity. We present here an overview of data supporting the idea that hypothalamic neuropeptide orexin A (OXA; hypocretin 1) may be a key component of brain mechanisms underlying obesity resistance. Prior work with models of obesity and obesity resistance in rodents has shown that increased orexin and/or orexin sensitivity is correlated with elevated spontaneous physical activity (SPA), and that orexin-induced SPA contributes to obesity resistance via increased non-exercise activity thermogenesis (NEAT). However, central hypothalamic orexin signaling mechanisms that regulate SPA remain undefined. Our ongoing studies and work of others support the hypothesis that one such mechanism may be upregulation of a hypoxia-inducible factor 1 alpha (HIF-1α)-dependent pathway, suggesting that orexin may promote obesity resistance both by increasing SPA and by influencing the metabolic state of orexin-responsive hypothalamic neurons. We discuss potential mechanisms based on both animal and in vitro pharmacological studies, in the context of elucidating potential molecular targets for obesity prevention and therapy.
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Affiliation(s)
- Tammy A. Butterick
- Minneapolis Veterans Affairs Health Care System, Research 151, One Veterans Drive, Minneapolis, MN USA 55417
| | - Charles J. Billington
- Minneapolis Veterans Affairs Health Care System, Research 151, One Veterans Drive, Minneapolis, MN USA 55417
- Department of Food Science and Nutrition, University of Minnesota, 225 Food Science and Nutrition, 1334 Eckles Avenue, St. Paul, MN USA 55108
- Department of Medicine, University of Minnesota Medical School, Suite 14-110 Phillips-Wangensteen Bldg, 420 Delaware Street SE, MMC 194, Minneapolis, MN USA 55455
| | - Catherine M. Kotz
- Minneapolis Veterans Affairs Health Care System, Research 151, One Veterans Drive, Minneapolis, MN USA 55417
- Department of Food Science and Nutrition, University of Minnesota, 225 Food Science and Nutrition, 1334 Eckles Avenue, St. Paul, MN USA 55108
| | - Joshua P. Nixon
- Minneapolis Veterans Affairs Health Care System, Research 151, One Veterans Drive, Minneapolis, MN USA 55417
- Department of Food Science and Nutrition, University of Minnesota, 225 Food Science and Nutrition, 1334 Eckles Avenue, St. Paul, MN USA 55108
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48
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Sokołowska P, Urbańska A, Biegańska K, Wagner W, Ciszewski W, Namiecińska M, Zawilska JB. Orexins protect neuronal cell cultures against hypoxic stress: an involvement of Akt signaling. J Mol Neurosci 2013; 52:48-55. [PMID: 24243084 PMCID: PMC3929148 DOI: 10.1007/s12031-013-0165-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 10/24/2013] [Indexed: 12/28/2022]
Abstract
Orexins A and B are peptides produced mainly by hypothalamic neurons that project to numerous brain structures. We have previously demonstrated that rat cortical neurons express both types of orexin receptors, and their activation by orexins initiates different intracellular signals. The present study aimed to determine the effect of orexins on the Akt kinase activation in the rat neuronal cultures and the significance of that response in neurons subjected to hypoxic stress. We report the first evidence that orexins A and B stimulated Akt in cortical neurons in a concentration- and time-dependent manner. Orexin B more potently than orexin A increased Akt phosphorylation, but the maximal effect of both peptides on the kinase activation was very similar. Next, cultured cortical neurons were challenged with cobalt chloride, an inducer of reactive oxygen species and hypoxia-mediated signaling pathways. Under conditions of chemical hypoxia, orexins potently increased neuronal viability and protected cortical neurons against oxidative stress. Our results also indicate that Akt kinase plays an important role in the pro-survival effects of orexins in neurons, which implies a possible mechanism of the orexin-induced neuroprotection.
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Affiliation(s)
- Paulina Sokołowska
- Institute of Medical Biology, Polish Academy of Sciences, Lodowa 106, 93-232, Łódź, Poland
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Schauwecker PE. Microarray-assisted fine mapping of quantitative trait loci on chromosome 15 for susceptibility to seizure-induced cell death in mice. Eur J Neurosci 2013; 38:3679-90. [PMID: 24001120 DOI: 10.1111/ejn.12351] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 08/08/2013] [Indexed: 11/30/2022]
Abstract
Prior studies with crosses of the FVB/NJ (FVB; seizure-induced cell death-susceptible) mouse and the C57BL/6J (B6; seizure-induced cell death-resistant) mouse revealed the presence of a quantitative trait locus (QTL) on chromosome 15 that influenced susceptibility to kainic acid-induced cell death (Sicd2). In an earlier study, we confirmed that the Sicd2 interval harbors gene(s) conferring strong protection against seizure-induced cell death through the creation of the FVB.B6-Sicd2 congenic strain, and created three interval-specific congenic lines (ISCLs) that encompass Sicd2 on chromosome 15 to fine-map this locus. To further localise this Sicd2 QTL, an additional congenic line carrying overlapping intervals of the B6 segment was created (ISCL-4), and compared with the previously created ISCL-1-ISCL-3 and assessed for seizure-induced cell death phenotype. Whereas all of the ISCLs showed reduced cell death associated with the B6 phenotype, ISCL-4, showed the most extensive reduction in seizure-induced cell death throughout all hippocampal subfields. In order to characterise the susceptibility loci on Sicd2 by use of this ISCL and identify compelling candidate genes, we undertook an integrative genomic strategy of comparing exon transcript abundance in the hippocampus of this newly developed chromosome 15 subcongenic line (ISCL-4) and FVB-like littermates. We identified 10 putative candidate genes that are alternatively spliced between the strains and may govern strain-dependent differences in susceptibility to seizure-induced excitotoxic cell death. These results illustrate the importance of identifying transcriptomics variants in expression studies, and implicate novel candidate genes conferring susceptibility to seizure-induced cell death.
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Affiliation(s)
- P E Schauwecker
- Department of Cell and Neurobiology, USC Keck School of Medicine, 1333 San Pablo Street, BMT 403, Los Angeles, CA, 90033, USA
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50
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Kukkonen JP. Lipid signaling cascades of orexin/hypocretin receptors. Biochimie 2013; 96:158-65. [PMID: 23810911 DOI: 10.1016/j.biochi.2013.06.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 06/18/2013] [Indexed: 11/18/2022]
Abstract
Orexins - orexin-A and orexin-B - are neuropeptides with significant role in regulation of fundamental physiological processes such as sleep-wakefulness cycle. Orexins act via G-protein-coupled OX1 and OX2 receptors, which are found, in addition to the central nervous system, also in a number of peripheral organs. Orexin receptors show high degree of signaling promiscuity. One particularly prominent way of signaling for these receptors is via phospholipase cascades, including the phospholipase C, phospholipase D and phospholipase A2 cascades, and also diacylglycerol lipase and phosphoinositide-3-kinase pathways. Most analyses have been performed in recombinant cells; there are indications of some of these cascades in native cells while the significance of other cascades remains to be shown. In this review, I present these pathways, their activation mechanisms and their physiological significance.
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Key Words
- 2-AG
- 2-arachidonoylglycerol
- AA
- CNS
- DAG
- DAG lipase
- DAGL
- DOG
- ERK
- Endocannabinoid
- G-protein-coupled receptor
- GPCR
- GPL
- Hypocretin
- IP(3)
- Ion fluxes
- KB-R7943
- MAFP
- N-acyl-phosphatidylethanolamine
- N-arachidonoylethanolamine
- NAPE
- NSCC
- OX(1)
- OX(2)
- Orexin
- PA
- PC
- PC-PLC
- PC-specific PLC
- PDK1
- PI
- PI3K
- PIP
- PIP(2)
- PIP(3)
- PIs
- PKB, PKC and PKD
- PLA(1), PLA(2), PLB, PLC and PLD
- Phospholipase
- TRP (channel)
- U73122
- a NCX inhibitor
- a PLC inhibitor
- a cPLA(2)α/ζ inhibitor
- anandamide
- arachidonic acid
- cPLA(2) and iPLA(2)
- central nervous system
- cytosolic (Ca(2+)-dependent) and intracellular (Ca(2+)-independent) PLA(2), respectively
- diacylglycerol
- dioctanoylglycerol
- extracellular signal-regulated kinase
- glycerophospholipid
- inositol-1,4,5-trisphosphate
- lyso(glycero)phospholipid
- lysoGPL
- lysoPA
- lysophosphatidic acid
- methyl arachidonyl fluorophosphonate
- non-selective cation channel
- orexin 1 receptor
- orexin 2 receptor
- phosphatidic acid
- phosphatidylcholine
- phosphatidylinositol
- phosphatidylinositol-3,4,5-trisphosphate
- phosphatidylinositol-4,5-bisphosphate
- phosphatidylinositolmonophosphate
- phosphatidylinositols (including differentially phosphorylated species PI, PIP, PIP(2) and PIP(3))
- phosphoinositide-3-kinase
- phosphoinositide-dependent kinase 1
- phospholipase A(1), A(2), B, C and D, respectively
- protein kinase B, C and D, respectively
- pyrrophenone
- transient receptor potential (channel)
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Affiliation(s)
- Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, POB 66, FIN-00014, University of Helsinki, Finland.
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