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Nirogi R, Jayarajan P, Benade V, Abraham R, Goyal VK. Hits and misses with animal models of narcolepsy and the implications for drug discovery. Expert Opin Drug Discov 2024; 19:755-768. [PMID: 38747534 DOI: 10.1080/17460441.2024.2354293] [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: 01/13/2024] [Accepted: 05/08/2024] [Indexed: 05/22/2024]
Abstract
INTRODUCTION Narcolepsy is a chronic and rare neurological disorder characterized by disordered sleep. Based on animal models and further research in humans, the dysfunctional orexin system was identified as a contributing factor to the pathophysiology of narcolepsy. Animal models played a larger role in the discovery of some of the pharmacological agents with established benefit/risk profiles. AREAS COVERED In this review, the authors examine the phenotypes observed in animal models of narcolepsy and the characteristics of clinically used pharmacological agents in these animal models. Additionally, the authors compare the effects of clinically used pharmacological agents on the phenotypes in animal models with those observed in narcolepsy patients. EXPERT OPINION Research in canine and mouse models have linked narcolepsy to the O×R2mutation and orexin deficiency, leading to new diagnostic criteria and a drug development focus. Advancements in pharmacological therapies have significantly improved narcolepsy management, with insights from both clinical experience and from animal models having led to new treatments such as low sodium oxybate and solriamfetol. However, challenges persist in addressing symptoms beyond excessive daytime sleepiness and cataplexy, highlighting the need for further research, including the development of diurnal animal models to enhance understanding and treatment options for narcolepsy.
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Affiliation(s)
- Ramakrishna Nirogi
- Drug Discovery & Development, Suven Life Sciences Limited, Hyderabad, India
| | - Pradeep Jayarajan
- Drug Discovery & Development, Suven Life Sciences Limited, Hyderabad, India
| | - Vijay Benade
- Drug Discovery & Development, Suven Life Sciences Limited, Hyderabad, India
| | - Renny Abraham
- Drug Discovery & Development, Suven Life Sciences Limited, Hyderabad, India
| | - Vinod Kumar Goyal
- Drug Discovery & Development, Suven Life Sciences Limited, Hyderabad, India
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2
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Abad VC. Pharmacological options for narcolepsy: are they the way forward? Expert Rev Neurother 2023; 23:819-834. [PMID: 37585269 DOI: 10.1080/14737175.2023.2249234] [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: 07/16/2023] [Revised: 08/13/2023] [Accepted: 08/14/2023] [Indexed: 08/18/2023]
Abstract
INTRODUCTION Narcolepsy is an under-recognized, rare neurologic disorder of hypersomnolence that is associated with increased mortality and medical and psychiatric co-morbidities. Narcolepsy exerts a substantial economic burden on patients and society. There is currently no cure, and life-long symptomatic therapy is needed. Available drugs do not modify the disease course. AREAS COVERED This manuscript provides an overview of narcolepsy symptoms, diagnosis, pathophysiology, current pharmacotherapies, and emerging treatments. Gaps and unresolved issues in diagnosis and management of narcolepsy are discussed to answer whether pharmacological options are the way forward. EXPERT OPINION Diagnostic criteria for narcolepsy (ICSD-3) need revision and greater clarity. Improved recognition of cataplexy and other symptoms through educational outreach, new biomarkers, improved test scoring through artificial intelligence algorithms, and use of machine learning may facilitate earlier diagnosis and treatment. Pharmacological options need improved symptomatic therapy in addition to targeted therapies that address the loss of hypocretin signaling. Optimal narcolepsy care also needs a better understanding of the pathophysiology, recognition of the different phenotypes in narcolepsy, identification of at-risk individuals and early recognition of symptoms, better diagnostic tools, and a database for research and disease monitoring of treatment, side-effects, and comorbidities.
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Affiliation(s)
- Vivien C Abad
- Division of Sleep Medicine, Department of Psychiatry and Behavioral Sciences Stanford University, Redwood, CA, USA
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3
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Pizza F, Barateau L, Dauvilliers Y, Plazzi G. The orexin story, sleep and sleep disturbances. J Sleep Res 2022; 31:e13665. [PMID: 35698789 DOI: 10.1111/jsr.13665] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 05/16/2022] [Accepted: 05/17/2022] [Indexed: 01/02/2023]
Abstract
The orexins, also known as hypocretins, are two neuropeptides (orexin A and B or hypocretin 1 and 2) produced by a few thousand neurons located in the lateral hypothalamus that were independently discovered by two research groups in 1998. Those two peptides bind two receptors (orexin/hypocretin receptor 1 and receptor 2) that are widely distributed in the brain and involved in the central physiological regulation of sleep and wakefulness, orexin receptor 2 having the major role in the maintenance of arousal. They are also implicated in a multiplicity of other functions, such as reward seeking, energy balance, autonomic regulation and emotional behaviours. The destruction of orexin neurons is responsible for the sleep disorder narcolepsy with cataplexy (type 1) in humans, and a defect of orexin signalling also causes a narcoleptic phenotype in several animal species. Orexin discovery is unprecedented in the history of sleep research, and pharmacological manipulations of orexin may have multiple therapeutic applications. Several orexin receptor antagonists were recently developed as new drugs for insomnia, and orexin agonists may be the next-generation drugs for narcolepsy. Given the broad range of functions of the orexin system, these drugs might also be beneficial for treating various conditions other than sleep disorders in the near future.
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Affiliation(s)
- Fabio Pizza
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.,IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
| | - Lucie Barateau
- Sleep-Wake Disorders Unit, Department of Neurology, Gui-de-Chauliac Hospital, CHU Montpellier, Montpellier, France.,National Reference Centre for Orphan Diseases, Narcolepsy, Idiopathic Hypersomnia, and Kleine-Levin Syndrome, Montpellier, France.,Institute for Neurosciences of Montpellier, University of Montpellier, INSERM, Montpellier, France
| | - Yves Dauvilliers
- Sleep-Wake Disorders Unit, Department of Neurology, Gui-de-Chauliac Hospital, CHU Montpellier, Montpellier, France.,National Reference Centre for Orphan Diseases, Narcolepsy, Idiopathic Hypersomnia, and Kleine-Levin Syndrome, Montpellier, France.,Institute for Neurosciences of Montpellier, University of Montpellier, INSERM, Montpellier, France
| | - Giuseppe Plazzi
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy.,Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
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Tisdale RK, Yamanaka A, Kilduff TS. Animal models of narcolepsy and the hypocretin/orexin system: Past, present, and future. Sleep 2021; 44:6031626. [PMID: 33313880 DOI: 10.1093/sleep/zsaa278] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 12/04/2020] [Indexed: 11/12/2022] Open
Abstract
Animal models have advanced not only our understanding of the etiology and phenotype of the sleep disorder narcolepsy but have also informed sleep/wake regulation more generally. The identification of an inheritable narcolepsy phenotype in dogs in the 1970s allowed the establishment of a breeding colony at Stanford University, resulting in studies that provided the first insights into the genetics and neurotransmitter systems that underlie cataplexy and rapid-eye movement sleep atonia. Although the discovery of the hypocretin/orexin neuropeptides in 1998 initially seemed unrelated to sleep/wake control, the description of the phenotype of the prepro-orexin knockout (KO) mouse as strongly resembling cataplexy, the pathognomonic symptom of narcolepsy, along with identification of a mutation in hypocretin receptor-2 gene as the source of canine narcolepsy, unequivocally established the relationship between this system and narcolepsy. The subsequent discovery of hypocretin neuron degeneration in human narcolepsy demystified a disorder whose etiology had been unknown since its initial description 120 years earlier. These breakthroughs prompted the development of numerous other animal models that have allowed manipulation of the hypocretin/orexin system, thereby advancing our understanding of sleep/wake circuitry. While animal models have greatly informed understanding of this fascinating disorder and the role of the hypocretin/orexin system in sleep/wake control, the question of why these neurons degenerate in human narcolepsy is only beginning to be understood. The development of new immune-mediated narcolepsy models are likely to further inform the etiology of this sleep disorder and animal models will undoubtedly play a critical role in the development of novel narcolepsy therapeutics.
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Affiliation(s)
- Ryan K Tisdale
- Center for Neuroscience, Biosciences Division, SRI International
| | - Akihiro Yamanaka
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Japan.,Department of Neural Regulation, Nagoya University Graduate School of Medicine, Japan
| | - Thomas S Kilduff
- Center for Neuroscience, Biosciences Division, SRI International
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Wang YQ, Liu WY, Li L, Qu WM, Huang ZL. Neural circuitry underlying REM sleep: A review of the literature and current concepts. Prog Neurobiol 2021; 204:102106. [PMID: 34144122 DOI: 10.1016/j.pneurobio.2021.102106] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 04/25/2021] [Accepted: 06/09/2021] [Indexed: 01/09/2023]
Abstract
As one of the fundamental sleep states, rapid eye movement (REM) sleep is believed to be associated with dreaming and is characterized by low-voltage, fast electroencephalographic activity and loss of muscle tone. However, the mechanisms of REM sleep generation have remained unclear despite decades of research. Several models of REM sleep have been established, including a reciprocal interaction model, limit-cycle model, flip-flop model, and a model involving γ-aminobutyric acid, glutamate, and aminergic/orexin/melanin-concentrating hormone neurons. In the present review, we discuss these models and summarize two typical disorders related to REM sleep, namely REM sleep behavior disorder and narcolepsy. REM sleep behavior disorder is a sleep muscle-tone-related disorder and can be treated with clonazepam and melatonin. Narcolepsy, with core symptoms of excessive daytime sleepiness and cataplexy, is strongly connected with orexin in early adulthood.
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Affiliation(s)
- Yi-Qun Wang
- Department of Pharmacology, School of Basic Medical Sciences and State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Wen-Ying Liu
- Department of Pharmacology, School of Basic Medical Sciences and State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Lei Li
- Department of Pharmacology, School of Basic Medical Sciences and State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Wei-Min Qu
- Department of Pharmacology, School of Basic Medical Sciences and State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Zhi-Li Huang
- Department of Pharmacology, School of Basic Medical Sciences and State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China.
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Murillo-Rodríguez E, Millán-Aldaco D, Palomero-Rivero M, Morales-Lara D, Mechoulam R, Drucker-Colín R. Cannabidiol Partially Blocks the Excessive Sleepiness in Hypocretindeficient Rats: Preliminary Data. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2020; 18:705-712. [PMID: 31642794 DOI: 10.2174/1871527318666191021143300] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 08/05/2019] [Accepted: 09/13/2019] [Indexed: 01/16/2023]
Abstract
BACKGROUND Excessive daytime sleepiness and cataplexy are among the symptoms of narcolepsy, a sleep disorder caused by the loss of hypocretin/orexin (HCRT/OX) neurons placed into the Hypothalamus (LH). Several treatments for managing narcolepsy include diverse drugs to induce alertness, such as antidepressants, amphetamine, or modafinil, etc. Recent evidence has shown that cannabidiol (CBD), a non-psychotropic derived from Cannabis sativa, shows positive therapeutic effects in neurodegenerative disorders, including Parkinson´s disease. Furthermore, CBD provokes alertness and enhances wake-related neurochemicals in laboratory animals. Thus, it is plausible to hypothesize that excessive somnolence observed in narcolepsy might be blocked by CBD. OBJECTIVE Here, we determined whether the systemic injection of CBD (5mg/kg, i.p.) would block the excessive sleepiness in a narcoleptic model. METHODS To test this idea, the neurotoxin hypocretin-2-saporin (HCRT2/SAP) was bilaterally injected into the LH of rats to eliminate HCRT leading to the establishment of narcoleptic-like behavior. Since excessive somnolence in HCRT2/SAP lesioned rats has been observed during the lights-off period, CBD was administered at the beginning of the dark phase. RESULTS Hourly analysis of sleep data showed that CBD blocked the sleepiness during the lights-off period across 7h post-injection in lesioned rats. CONCLUSION Taking together, these preliminary findings suggest that CBD might prevent sleepiness in narcolepsy.
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Affiliation(s)
- Eric Murillo-Rodríguez
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud, Universidad Anáhuac Mayab, Mérida, Yucatán, Mexico.,Intercontinental Neuroscience Research Group, Merida, Yucatán, Mexico
| | - Diana Millán-Aldaco
- Depto. de Neurociencia Cognitiva, División de Neurociencias, Instituto de Fisiología Celular. Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Marcela Palomero-Rivero
- Depto. de Neuropatología Molecular, División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Daniela Morales-Lara
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud, Universidad Anáhuac Mayab, Mérida, Yucatán, Mexico.,Intercontinental Neuroscience Research Group, Merida, Yucatán, Mexico
| | - Raphael Mechoulam
- Institute for Drug Research, Medical Faculty, Hebrew University, Jerusalem, Israel
| | - René Drucker-Colín
- Depto. de Neuropatología Molecular, División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
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Tang H, Zhu Q, Li W, Qin S, Gong Y, Wang H, Shioda S, Li S, Huang J, Liu B, Fang Y, Liu Y, Wang S, Guo Y, Xia Q, Guo Y, Xu Z. Neurophysiology and Treatment of Disorders of Consciousness Induced by Traumatic Brain Injury: Orexin Signaling as a Potential Therapeutic Target. Curr Pharm Des 2020; 25:4208-4220. [PMID: 31663471 DOI: 10.2174/1381612825666191029101830] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 10/21/2019] [Indexed: 02/07/2023]
Abstract
BACKGROUND Traumatic brain injury (TBI) can cause disorders of consciousness (DOC) by impairing the neuronal circuits of the ascending reticular activating system (ARAS) structures, including the hypothalamus, which are responsible for the maintenance of the wakefulness and awareness. However, the effectiveness of drugs targeting ARAS activation is still inadequate, and novel therapeutic modalities are urgently needed. METHODS The goal of this work is to describe the neural loops of wakefulness, and explain how these elements participate in DOC, with emphasis on the identification of potential new therapeutic options for DOC induced by TBI. RESULTS Hypothalamus has been identified as a sleep/wake center, and its anterior and posterior regions have diverse roles in the regulation of the sleep/wake function. In particular, the posterior hypothalamus (PH) possesses several types of neurons, including the orexin neurons in the lateral hypothalamus (LH) with widespread projections to other wakefulness-related regions of the brain. Orexins have been known to affect feeding and appetite, and recently their profound effect on sleep disorders and DOC has been identified. Orexin antagonists are used for the treatment of insomnia, and orexin agonists can be used for narcolepsy. Additionally, several studies demonstrated that the agonists of orexin might be effective in the treatment of DOC, providing novel therapeutic opportunities in this field. CONCLUSION The hypothalamic-centered orexin has been adopted as the point of entry into the system of consciousness control, and modulators of orexin signaling opened several therapeutic opportunities for the treatment of DOC.
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Affiliation(s)
- Huiling Tang
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Qiumei Zhu
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Wei Li
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Siru Qin
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yinan Gong
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Hong Wang
- Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Seiji Shioda
- Peptide Drug Innovation, Global Research Center for Innovative Life Science, Hoshi University School of Pharmacy and Pharmaceutical Sciences, 2-4-41 Ebara, Shinagawa, Tokyo 142-8501, Japan
| | - Shanshan Li
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Jin Huang
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Baohu Liu
- Department of Rehabilitation, Wangjing Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yuxin Fang
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yangyang Liu
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Shenjun Wang
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yongming Guo
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Qing Xia
- Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yi Guo
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,College of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Zhifang Xu
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
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Equihua-Benítez AC, Equihua-Benítez JA, Guzmán-Vásquez K, Prospero-García O, Drucker-Colín R. Orexin cell transplant reduces behavioral arrest severity in narcoleptic mice. Brain Res 2020; 1745:146951. [PMID: 32531224 DOI: 10.1016/j.brainres.2020.146951] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 03/29/2020] [Accepted: 06/05/2020] [Indexed: 12/14/2022]
Abstract
Narcolepsy is a sleep disorder that has been associated with the loss of orexinergic neurons from the lateral hypothalamic area. This loss leads to dysregulated sleep and cataplexy attacks. Therapeutic options are currently limited to symptom management with pharmacotherapy and nonpharmacological approaches. Nonetheless, cell replacement therapy could offer relief, and research in the field has yielded positive results for other neurodegenerative disorders, such as Parkinson's disease. Thus, we propose that orexin cell rich grafts could help improve narcoleptic symptoms in the orexin/ataxin-3 mouse model of narcolepsy. For this purpose, we isolated EGFP+ cells from either orexin/EGFP or CAG-EGFP mice with the use of a flow cytometer and grafted them into the pedunculopontine and laterodorsal tegmentum nuclei (PPT/LDDT) of orexin/ataxin-3 mice. Our results show that even small orexinergic grafts can reduce the severity of behavioral arrests, with a median reduction of 30.31% in episode duration, 51.35% for number of events and 69.73% in time spent in the behavioral arrest state and help with sleep fragmentation measured in number of bouts per behavioral state. Surprisingly, control grafts made from cerebellar tissue also reduced behavioral arrest severity, but to a lesser degree. Although still at a very early stage, these results show that there is potential in cell grafts for improving aspects of the narcoleptic phenotype and further research could help elucidate realistic expectations of an orexin cell replacement therapy for narcolepsy.
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Affiliation(s)
- Ana Clementina Equihua-Benítez
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacán, Ciudad de México 04510, Mexico.
| | - Julián A Equihua-Benítez
- Dirección General de Proyectos Interinstitucionales, Consejo Nacional para el Conocimiento y Uso de la Biodiversidad, Insurgentes Sur 4903, Parques del Pedregal, Tlalpan, Ciudad de México 14010, Mexico.
| | - Khalil Guzmán-Vásquez
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacán, Ciudad de México 04510, Mexico
| | - Oscar Prospero-García
- Laboratorio de Cannabinoides, Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, Circuito Interior, Ciudad Universitaria, Ciudad de México 04510, Mexico.
| | - René Drucker-Colín
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacán, Ciudad de México 04510, Mexico
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9
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Barateau L, Dauvilliers Y. Recent advances in treatment for narcolepsy. Ther Adv Neurol Disord 2019; 12:1756286419875622. [PMID: 31632459 PMCID: PMC6767718 DOI: 10.1177/1756286419875622] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/21/2019] [Indexed: 11/17/2022] Open
Abstract
Narcolepsy type 1 (NT1) is a chronic orphan disorder, caused by the selective and irreversible loss of hypocretin/orexin (ORX) neurons, by a probable autoimmune process. Little is known about NT2 etiology and prevalence, sharing with NT1 excessive daytime sleepiness (EDS) and dysregulation of rapid eye movement (REM) sleep, but without cataplexy and loss of ORX neurons. Despite major advances in our understanding of the neurobiological basis of NT1, management remains nowadays only symptomatic. The main and most disabling symptom, EDS, is managed with psychostimulants, as modafinil/armodafinil, methylphenidate, or amphetamines as a third-line therapy. Narcolepsy is an active area for drug development, and new wake-promoting agents have been developed over the past years. Pitolisant, a selective histamine H3 receptor inverse agonist, has been recently approved to treat patients with NT1 and NT2. Solriamfetol, a phenylalanine derivative with dopaminergic and noradrenergic activity will be soon a new therapeutic option to treat EDS in NT1 and NT2. Sodium oxybate, used for decades in adult patients with narcolepsy, was recently shown to be effective and safe in childhood narcolepsy. The discovery of ORX deficiency in NT1 opened new therapeutic options oriented towards ORX-based therapies, especially nonpeptide ORX receptor agonists that are currently under development. In addition, immune-based therapies administered as early as possible after disease onset could theoretically slow down or stop the destruction of ORX neurons in some selected patients. Further well-designed controlled trials are required to determine if they could really impact on the natural history of the disease. Given the different clinical, biological and genetic profiles, narcolepsy may provide a nice example for developing personalized medicine in orphan diseases, that could ultimately aid in similar research and clinical efforts for other conditions.
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Affiliation(s)
- Lucie Barateau
- Service de Neurologie, Gui-de-Chauliac Hospital,
Montpellier, France; Sleep-Wake Disorders Center, Gui-de-Chauliac Hospital,
CHU Montpellier, France; National Reference Network for Narcolepsy,
Montpellier, France; Inserm U1061, Montpellier, France
| | - Yves Dauvilliers
- Service de Neurologie, Gui-de-Chauliac Hospital,
CHU Montpellier, 80 avenue Augustin Fliche, 34295 Montpellier Cedex 5,
France
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10
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Nepovimova E, Janockova J, Misik J, Kubik S, Stuchlik A, Vales K, Korabecny J, Mezeiova E, Dolezal R, Soukup O, Kobrlova T, Pham NL, Nguyen TD, Konecny J, Kuca K. Orexin supplementation in narcolepsy treatment: A review. Med Res Rev 2018; 39:961-975. [PMID: 30426515 DOI: 10.1002/med.21550] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Revised: 09/20/2018] [Accepted: 10/19/2018] [Indexed: 12/22/2022]
Abstract
Narcolepsy is a rare, chronic neurological disease characterized by excessive daytime sleepiness, cataplexy, vivid hallucinations, and sleep paralysis. Narcolepsy occurs in approximately 1 of 3000 people, affecting mainly adolescents aged 15 to 30 years. Recently, people with narcolepsy were shown to exhibit extensive orexin/hypocretin neuronal loss. The orexin system regulates sleep/wake control via complex interactions with monoaminergic, cholinergic and GABA-ergic neuronal systems. Currently, no cure for narcolepsy exists, but some symptoms can be controlled with medication (eg, stimulants, antidepressants, etc). Orexin supplementation represents a more sophisticated way to treat narcolepsy because it addresses the underlying cause of the disease and not just the symptoms. Research on orexin supplementation in the treatment of sleep disorders has strongly increased over the past two decades. This review focuses on a brief description of narcolepsy, the mechanisms by which the orexin system regulates sleep/wake cycles, and finally, possible therapeutic options based on orexin supplementation in animal models and patients with narcolepsy.
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Affiliation(s)
- Eugenie Nepovimova
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic
| | - Jana Janockova
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Jan Misik
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Stepan Kubik
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague 4, Czech Republic
| | - Ales Stuchlik
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague 4, Czech Republic
| | - Karel Vales
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague 4, Czech Republic
| | - Jan Korabecny
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Eva Mezeiova
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Rafael Dolezal
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic.,Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Ondrej Soukup
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Tereza Kobrlova
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Ngoc Lam Pham
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic.,Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Thuy Duong Nguyen
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic.,Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Jan Konecny
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Kamil Kuca
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic.,Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
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12
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de Biase S, Nilo A, Gigli GL, Valente M. Investigational therapies for the treatment of narcolepsy. Expert Opin Investig Drugs 2017; 26:953-963. [PMID: 28726523 DOI: 10.1080/13543784.2017.1356819] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
INTRODUCTION Narcolepsy is a chronic sleep disorder characterized by a pentad of excessive daytime sleepiness (EDS), cataplexy, sleep paralysis, hypnagogic/hypnopompic hallucinations, and disturbed nocturnal sleep. While non-pharmacological treatments are sometimes helpful, more than 90% of narcoleptic patients require a pharmacological treatment. Areas covered: The present review is based on an extensive Internet and PubMed search from 1994 to 2017. It is focused on drugs currently in development for the treatment of narcolepsy. Expert opinion: Currently there is no cure for narcolepsy, with treatment focusing on symptoms control. However, these symptomatic treatments are often unsatisfactory. The research is leading to a better understanding of narcolepsy and its symptoms. New classes of compounds with possible applications in the development of novel stimulant/anticataplectic medications are described. H3 receptor antagonists represent a new therapeutic option for EDS in narcolepsy. JZP-110, with its distinct mechanism of action, would be a new therapeutic option for the treatment of EDS in the coming years. In the future, hypocretin-based therapies and immune-based therapies, could modify the clinical course of the disease. However, more information would be necessary to completely understand the autoimmune process and also how this process can be altered for therapeutic benefits.
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Affiliation(s)
- Stefano de Biase
- a Neurology Unit, Department of Experimental and Clinical Medical Sciences , University of Udine Medical School , Udine , Italy
| | - Annacarmen Nilo
- a Neurology Unit, Department of Experimental and Clinical Medical Sciences , University of Udine Medical School , Udine , Italy
| | - Gian Luigi Gigli
- a Neurology Unit, Department of Experimental and Clinical Medical Sciences , University of Udine Medical School , Udine , Italy.,b Department of Neurosciences , "S. Maria della Misericordia" University Hospital Udine , Udine , Italy
| | - Mariarosaria Valente
- a Neurology Unit, Department of Experimental and Clinical Medical Sciences , University of Udine Medical School , Udine , Italy.,b Department of Neurosciences , "S. Maria della Misericordia" University Hospital Udine , Udine , Italy
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Kallweit U, Bassetti CL. Pharmacological management of narcolepsy with and without cataplexy. Expert Opin Pharmacother 2017; 18:809-817. [PMID: 28443381 DOI: 10.1080/14656566.2017.1323877] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Ulf Kallweit
- Department of Neurology, Bern University Hospital and University of Bern, Bern, Switzerland
- Department of Neurology, Narcolepsy-Center, HELIOS Klinik Hagen Ambrock, Hagen, Germany
- Department of Rehabilitation, University of Witten/Herdecke, Witten, Germany
| | - Claudio L. Bassetti
- Department of Neurology, Bern University Hospital and University of Bern, Bern, Switzerland
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Abstract
Narcolepsy is a life-long, underrecognized sleep disorder that affects 0.02%-0.18% of the US and Western European populations. Genetic predisposition is suspected because of narcolepsy's strong association with HLA DQB1*06-02, and genome-wide association studies have identified polymorphisms in T-cell receptor loci. Narcolepsy pathophysiology is linked to loss of signaling by hypocretin-producing neurons; an autoimmune etiology possibly triggered by some environmental agent may precipitate hypocretin neuronal loss. Current treatment modalities alleviate the main symptoms of excessive daytime somnolence (EDS) and cataplexy and, to a lesser extent, reduce nocturnal sleep disruption, hypnagogic hallucinations, and sleep paralysis. Sodium oxybate (SXB), a sodium salt of γ hydroxybutyric acid, is a first-line agent for cataplexy and EDS and may help sleep disruption, hypnagogic hallucinations, and sleep paralysis. Various antidepressant medications including norepinephrine serotonin reuptake inhibitors, selective serotonin reuptake inhibitors, and tricyclic antidepressants are second-line agents for treating cataplexy. In addition to SXB, modafinil and armodafinil are first-line agents to treat EDS. Second-line agents for EDS are stimulants such as methylphenidate and extended-release amphetamines. Emerging therapies include non-hypocretin-based therapy, hypocretin-based treatments, and immunotherapy to prevent hypocretin neuronal death. Non-hypocretin-based novel treatments for narcolepsy include pitolisant (BF2.649, tiprolisant); JZP-110 (ADX-N05) for EDS in adults; JZP 13-005 for children; JZP-386, a deuterated sodium oxybate oral suspension; FT 218 an extended-release formulation of SXB; and JNJ-17216498, a new formulation of modafinil. Clinical trials are investigating efficacy and safety of SXB, modafinil, and armodafinil in children. γ-amino butyric acid (GABA) modulation with GABAA receptor agonists clarithromycin and flumazenil may help daytime somnolence. Other drugs investigated include GABAB agonists (baclofen), melanin-concentrating hormone antagonist, and thyrotropin-releasing hormone agonists. Hypocretin-based therapies include hypocretin peptide replacement administered either through an intracerebroventricular route or intranasal route. Hypocretin neuronal transplant and transforming stem cells into hypothalamic neurons are also discussed in this article. Immunotherapy to prevent hypocretin neuronal death is reviewed.
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Affiliation(s)
- Vivien C Abad
- Department of Psychiatry and Behavioral Sciences, Division of Sleep Medicine, Stanford University Outpatient Center, Redwood City, CA, USA
| | - Christian Guilleminault
- Department of Psychiatry and Behavioral Sciences, Division of Sleep Medicine, Stanford University Outpatient Center, Redwood City, CA, USA
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16
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Abstract
Narcolepsy type 1 and narcolepsy type 2 are central disorders of hypersomnolence. Narcolepsy type 1 is characterized by excessive daytime sleepiness and cataplexy and is associated with hypocretin-1 deficiency. On the other hand, in narcolepsy type 2, cerebrospinal fluid hypocretin-1 levels are normal and cataplexy absent. Despite major advances in our understanding of narcolepsy mechanisms, its current management is only symptomatic. Treatment options may vary from a single drug that targets several symptoms, or multiple medications that each treats a specific symptom. In recent years, narcolepsy treatment has changed with the widespread use of modafinil/armodafinil for daytime sleepiness, antidepressants (selective serotonin and dual serotonin and noradrenalin reuptake inhibitors) for cataplexy, and sodium oxybate for both symptoms. Other psychostimulants can also be used, such as methylphenidate, pitolisant and rarely amphetamines, as third-line therapy. Importantly, clinically relevant subjective and objective measures of daytime sleepiness are required to monitor the treatment efficacy and to provide guidance on whether the treatment goals are met. Associated symptoms and comorbid conditions, such as hypnagogic/hypnopompic hallucinations, sleep paralysis, disturbed nighttime sleep, unpleasant dreams, REM- and non REM-related parasomnias, depressive symptoms, overweight/obesity, and obstructive sleep apnea, should also be taken into account and managed, if required. In the near future, the efficacy of new wake-promoting drugs, anticataplectic agents, hypocretin replacement therapy and immunotherapy at the early stages of the disease should also be evaluated.
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Affiliation(s)
- Lucie Barateau
- Department of Neurology, Service de Neurologie, Sleep-Wake Disorders Center, Hôpital Gui-de-Chauliac, CHU Montpellier, 80 avenue Augustin Fliche, 34295, Montpellier Cedex 5, France.,National Reference Network for Narcolepsy, Montpellier, France.,Inserm U1061, Montpellier, France
| | - Régis Lopez
- Department of Neurology, Service de Neurologie, Sleep-Wake Disorders Center, Hôpital Gui-de-Chauliac, CHU Montpellier, 80 avenue Augustin Fliche, 34295, Montpellier Cedex 5, France.,National Reference Network for Narcolepsy, Montpellier, France.,Inserm U1061, Montpellier, France
| | - Yves Dauvilliers
- Department of Neurology, Service de Neurologie, Sleep-Wake Disorders Center, Hôpital Gui-de-Chauliac, CHU Montpellier, 80 avenue Augustin Fliche, 34295, Montpellier Cedex 5, France. .,National Reference Network for Narcolepsy, Montpellier, France. .,Inserm U1061, Montpellier, France.
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18
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Liu J, Merkle FT, Gandhi AV, Gagnon JA, Woods IG, Chiu CN, Shimogori T, Schier AF, Prober DA. Evolutionarily conserved regulation of hypocretin neuron specification by Lhx9. Development 2015; 142:1113-24. [PMID: 25725064 DOI: 10.1242/dev.117424] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Loss of neurons that express the neuropeptide hypocretin (Hcrt) has been implicated in narcolepsy, a debilitating disorder characterized by excessive daytime sleepiness and cataplexy. Cell replacement therapy, using Hcrt-expressing neurons generated in vitro, is a potentially useful therapeutic approach, but factors sufficient to specify Hcrt neurons are unknown. Using zebrafish as a high-throughput system to screen for factors that can specify Hcrt neurons in vivo, we identified the LIM homeobox transcription factor Lhx9 as necessary and sufficient to specify Hcrt neurons. We found that Lhx9 can directly induce hcrt expression and we identified two potential Lhx9 binding sites in the zebrafish hcrt promoter. Akin to its function in zebrafish, we found that Lhx9 is sufficient to specify Hcrt-expressing neurons in the developing mouse hypothalamus. Our results elucidate an evolutionarily conserved role for Lhx9 in Hcrt neuron specification that improves our understanding of Hcrt neuron development.
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Affiliation(s)
- Justin Liu
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Florian T Merkle
- Departments of Molecular and Cellular Biology, and Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA
| | - Avni V Gandhi
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - James A Gagnon
- Departments of Molecular and Cellular Biology, and Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Ian G Woods
- Departments of Molecular and Cellular Biology, and Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Cindy N Chiu
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | | | - Alexander F Schier
- Departments of Molecular and Cellular Biology, and Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA Division of Sleep Medicine, Harvard University, Cambridge, MA 02115, USA
| | - David A Prober
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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Wozniak DR, Quinnell TG. Unmet needs of patients with narcolepsy: perspectives on emerging treatment options. Nat Sci Sleep 2015; 7:51-61. [PMID: 26045680 PMCID: PMC4447169 DOI: 10.2147/nss.s56077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The treatment options currently available for narcolepsy are often unsatisfactory due to suboptimal efficacy, troublesome side effects, development of drug tolerance, and inconvenience. Our understanding of the neurobiology of narcolepsy has greatly improved over the last decade. This knowledge has not yet translated into additional therapeutic options for patients, but progress is being made. Some compounds, such as histaminergic H3 receptor antagonists, may prove useful in symptom control of narcolepsy. The prospect of finding a cure still seems distant, but hypocretin replacement therapy offers some promise. In this narrative review, we describe these developments and others which may yield more effective narcolepsy treatments in the future.
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Affiliation(s)
- Dariusz R Wozniak
- Respiratory Support and Sleep Centre, Papworth Hospital, Cambridge, UK
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20
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Thorpy MJ, Dauvilliers Y. Clinical and practical considerations in the pharmacologic management of narcolepsy. Sleep Med 2015; 16:9-18. [PMID: 25458251 DOI: 10.1016/j.sleep.2014.10.002] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 10/07/2014] [Accepted: 10/09/2014] [Indexed: 12/15/2022]
Affiliation(s)
- Michael J Thorpy
- Sleep-Wake Disorders Center, Montefiore Medical Center, Bronx, NY, USA.
| | - Yves Dauvilliers
- National Reference Network for Narcolepsy, Sleep-Wake Disorders Center, Department of Neurology, Gui-de-Chauliac Hospital, CHU Montpellier, INSERM U1061, France
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21
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Anderson KN. An update in sleep neurology: the latest bedtime stories. J Neurol 2014; 262:487-91. [PMID: 25491077 DOI: 10.1007/s00415-014-7602-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 11/27/2014] [Indexed: 01/17/2023]
Abstract
In the 24/7 modern society, sleep disorders and the role of normal amounts and timing of sleep for health are often neglected by both doctors and their patients. Sleep has been said to be "of the brain, by the brain and for the brain" and the most immediate and obvious consequence of disrupted sleep is impaired brain function. This review will cover some of the recent papers published in both the Journal of Neurology and elsewhere in 2013/2014 that have advanced our knowledge of sleep and circadian rhythm disorders.
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Affiliation(s)
- K N Anderson
- Regional Sleep Service, Freeman Hospital, Newcastle Upon Tyne, UK,
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22
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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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Partinen M, Kornum BR, Plazzi G, Jennum P, Julkunen I, Vaarala O. Narcolepsy as an autoimmune disease: the role of H1N1 infection and vaccination. Lancet Neurol 2014; 13:600-13. [PMID: 24849861 DOI: 10.1016/s1474-4422(14)70075-4] [Citation(s) in RCA: 190] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Narcolepsy is a sleep disorder characterised by loss of hypothalamic hypocretin (orexin) neurons. The prevalence of narcolepsy is about 30 per 100 000 people, and typical age at onset is 12-16 years. Narcolepsy is strongly associated with the HLA-DQB1*06:02 genotype, and has been thought of as an immune-mediated disease. Other risk genes, such as T-cell-receptor α chain and purinergic receptor subtype 2Y11, are also implicated. Interest in narcolepsy has increased since the epidemiological observations that H1N1 infection and vaccination are potential triggering factors, and an increase in the incidence of narcolepsy after the pandemic AS03 adjuvanted H1N1 vaccination in 2010 from Sweden and Finland supports the immune-mediated pathogenesis. Epidemiological observations from studies in China also suggest a role for H1N1 virus infections as a trigger for narcolepsy. Although the pathological mechanisms are unknown, an H1N1 virus-derived antigen might be the trigger.
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Affiliation(s)
- Markku Partinen
- Helsinki Sleep Clinic, Vitalmed Research Centre, Helsinki, Finland; Department of Clinical Neurosciences, University of Helsinki, Helsinki, Finland.
| | - Birgitte Rahbek Kornum
- Molecular Sleep Laboratory, Department of Diagnostics, Glostrup Hospital, Glostrup, Denmark
| | - Giuseppe Plazzi
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Italy; IRCCS Istituto delle Scienze Neurologiche, Bologna, Italy
| | - Poul Jennum
- Danish Center for Sleep Medicine, Department of Clinical Neurophysiology, University of Copenhagen, Glostrup Hospital, Glostrup, Denmark
| | - Ilkka Julkunen
- Department of Virology, University of Turku, Turku, Finland; Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare, Helsinki, Finland
| | - Outi Vaarala
- Department of Vaccines and Immune Protection, National Institute for Health and Welfare, Helsinki, Finland
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