Orexin B
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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.
- MeSH
- genetická terapie MeSH
- knihovny malých molekul chemie farmakologie MeSH
- lidé MeSH
- narkolepsie farmakoterapie genetika MeSH
- orexiny terapeutické užití MeSH
- transplantace buněk MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
The neuropeptides, orexin A and orexin B (also known as hypocretins), are produced in hypothalamic neurons and belong to ligands for orphan G protein-coupled receptors. Generally, the primary role of orexins is to act as excitatory neurotransmitters and regulate the sleep process. Lack of orexins may lead to sleep disorder narcolepsy in mice, dogs, and humans. Narcolepsy is a neurological disorder of alertness characterized by a decrease of ability to manage sleep-wake cycles, excessive daytime sleepiness, and other symptoms, such as cataplexy, vivid hallucinations, and paralysis. Thus, the discovery of orexin receptors, modulators, and their causal implication in narcolepsy is the most important advance in sleep-research. The presented work is focused on the evaluation of compounds L1−L11 selected by structure-based virtual screening for their ability to modulate orexin receptor type 2 (OX2R) in comparison with standard agonist orexin-A together with their blood-brain barrier permeability and cytotoxicity. We can conclude that the studied compounds possess an affinity towards the OX2R. However, the compounds do not have intrinsic activity and act as the antagonists of this receptor. It was shown that L4 was the most potent antagonistic ligand to orexin A and displayed an IC50 of 2.2 μM, offering some promise mainly for the treatment of insomnia.
- MeSH
- antagonisté orexinových receptorů chemie farmakologie MeSH
- CHO buňky MeSH
- Cricetulus MeSH
- inhibiční koncentrace 50 MeSH
- kvantitativní vztahy mezi strukturou a aktivitou MeSH
- ligandy MeSH
- molekulární konformace MeSH
- molekulární modely * MeSH
- molekulární struktura MeSH
- orexinové receptory chemie MeSH
- orexiny chemie farmakologie MeSH
- počítačová simulace * MeSH
- racionální návrh léčiv * MeSH
- vazba proteinů MeSH
- vazebná místa MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Background The hypocretin/orexin system has been shown to play a role in heart failure. Whether it also influences myocardial infarction (MI) outcomes is unknown. We evaluated the effect of the rs7767652 minor allele T associated with decreased transcription of the hypocretin/orexin receptor-2 and circulating orexin A concentrations on mortality risk after MI. Methods and Results Data from a single-center, prospectively designed registry of consecutive patients hospitalized for MI at a large tertiary cardiology center were analyzed. Patients without previous history of MI or heart failure were included. A random population sample was used to compare allele frequencies in the general population. Out of 1009 patients (aged 64±12 years, 74.6% men) after MI, 6.1% were homozygotes (TT) and 39.4% heterozygotes (CT) for minor allele. Allele frequencies in the MI group did not differ from 1953 subjects from general population (χ2P=0.62). At index hospitalization, MI size was the same, but ventricular fibrillation and the need for cardiopulmonary resuscitation were more prevalent in the TT allele variant. Among patients with ejection fraction ≤40% at discharge, the TT variant was associated with a lower increase in left ventricular ejection fraction during follow-up (P=0.03). During the 27-month follow-up, there was a statistically significant association of the TT variant with increased mortality risk (hazard ratio [HR], 2.83; P=0.001). Higher circulating orexin A was associated with a lower mortality risk (HR, 0.41; P<0.05). Conclusions Attenuation of hypocretin/orexin signaling is associated with increased mortality risk after MI. This effect may be partially explained by the increased arrhythmic risk and the effect on the left ventricular systolic function recovery.
In this study, we investigated the stability of the fully activated conformation of the orexin receptor 2 (OX2R) embedded in a pure POPC bilayer using MD simulations. Various thermodynamic ensembles (i.e., NPT, NVT, NVE, NPAT, μVT, and NPγT) were employed to explore the dynamical heterogeneity of the system in a comprehensive way. In addition, informational similarity metrics (e.g., Jensen-Shannon divergence) as well as Markov state modeling approaches were utilized to elucidate the receptor kinetics. Special attention was paid to assessing surface tension within the simulation box, particularly under NPγT conditions, where 21 nominal surface tension constants were evaluated. Our findings suggest that traditional thermodynamic ensembles such as NPT may not adequately control physical properties of the POPC membrane, impacting the plausibility of the OX2R model. In general, the performed study underscores the importance of employing the NPγT ensemble for computational investigations of membrane-embedded receptors, as it effectively maintains zero surface tension in the simulated system. These results offer valuable insights for future research aimed at understanding receptor dynamics and designing targeted therapeutics.
YNT-185 is the first known small molecule acting as orexin 2 receptor (OX2R) agonist with implication to narcolepsy treatment, served as a template scaffold in generating a small set of seven compounds with predictive affinity to OX2R. The design of the new small molecules was driven mostly by improving physicochemical properties of the parent drug YNT-185 in parallel with in silico studies, later suggesting their favorable binding modes within the active site of OX2R. We obtained seven new potential OX2R binders that were evaluated in vitro for their CNS availability, cytotoxicity, and behavior pattern on OX2R. Out of them, 15 emerged as the most potent modulator of OX2R, which, contrary to YNT-185, displayed inverse mode of action, i.e. antagonist profile. 15 was also submitted to an in vivo experiment revealing its ability to permeate through BBB into the brain with a short half-life.
- MeSH
- aniliny farmakologie terapeutické užití MeSH
- benzamidy farmakologie terapeutické užití MeSH
- lidé MeSH
- molekulární struktura MeSH
- orexinové receptory terapeutické užití MeSH
- poruchy iniciace a udržování spánku farmakoterapie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Klíčová slova
- hypokretiny, orexin-A (hypokretin-1), orexin-B (hypokretin-2),
- MeSH
- energetický metabolismus fyziologie MeSH
- lidé MeSH
- narkolepsie * etiologie MeSH
- neuropeptidy * biosyntéza fyziologie sekrece MeSH
- obezita etiologie MeSH
- orexinové receptory MeSH
- regulace chuti k jídlu * fyziologie MeSH
- stravovací zvyklosti fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
Orexins (orexin A and B) are initially known to be a hypothalamic peptide critical for feeding and normal wakefulness. In addition, emerging evidence from behavioral tests suggests that orexins are also involved in the regulation of nociceptive processing, suggesting a novel potential therapeutic approach for pain treatment. Both spinal and supraspinal mechanisms appear to contribute to the role of orexin in nociception. In the spinal cord, dorsal root ganglion (DRG) neurons are primary afferent neurons that transmit peripheral stimuli to the pain-processing areas. Morphological results show that both orexin A and orexin- 1 receptor are distributed in DRG neurons. Moreover, by using whole-cell patch-clamp recordings and calcium imaging measurements we found that orexin A induced excitability and intracellular calcium concentration elevation in the isolated rat DRG neurons, which was mainly dependent on the activation of spinal orexin-1 receptor. Based on these findings, we propose a hypothesis that the direct effect of orexin A on DRG neurons would represent a possible mechanism for the orexinergic modulation of spinal nociceptive transmission.
- Klíčová slova
- Orexins, Nociceptive transmission, Dorsal root ganglion neurons, Spinal cord, Orexin-1 receptor, Patch clamp, Calcium imaging,
- MeSH
- akční potenciály MeSH
- benzoxazoly farmakologie MeSH
- bolest metabolismus MeSH
- intracelulární signální peptidy a proteiny metabolismus MeSH
- krysa rodu rattus MeSH
- močovina analogy a deriváty farmakologie MeSH
- nervový přenos účinky léků MeSH
- neurony metabolismus účinky léků MeSH
- neuropeptidy metabolismus MeSH
- potkani Sprague-Dawley MeSH
- receptory neuropeptidů antagonisté a inhibitory metabolismus MeSH
- receptory spřažené s G-proteiny antagonisté a inhibitory metabolismus MeSH
- spinální ganglia cytologie metabolismus účinky léků MeSH
- vápníková signalizace MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Klíčová slova
- spontánní pohybová aktivita,
- MeSH
- bdění účinky léků MeSH
- centrální nervový systém účinky léků MeSH
- kognice účinky léků MeSH
- lidé MeSH
- modely nemocí na zvířatech MeSH
- orexiny * terapeutické užití MeSH
- regulace chuti k jídlu účinky léků MeSH
- spánek účinky léků MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- práce podpořená grantem MeSH
- přehledy MeSH
BACKGROUND AND OBJECTIVES: Nonconvulsive status epilepticus (NCSE) manifests as a change in mental status without a coma (NCSE proper) or comatose NCSE. Hypocretin-1/orexin-A (H/O) is involved in alertness and sleep maintenance. Sleep impairment and excessive daytime sleepiness (EDS) have a negative impact on cognitive functions and activities of daily living (ADL). METHODS: Patients meeting the NCSE criteria underwent cerebrospinal fluid and brain magnetic resonance imaging examinations, polysomnographies (PSG), multiple latency sleep tests (MSLT), and completed Epworth Sleepiness Scale (ESS). Montreal Cognitive Assessment was used to evaluate cognitive functions, and the Barthel Index was used to assess ADL in the acute phase (V1) and three months follow-up (V2). RESULTS: From May 2020 to May 2023, we enrolled 15 patients, eight (53.3 %) women, with a median age of 69 (14) years. The median H/O CSF concentration was 250 (63.6) pg/ml; however, only three CSF samples (20 %) decreased below the borderline concentration of 200 pg/ml. Fourteen out of 15 patients (93.3 %) completed the PSG study. The median of wakefulness after sleep onset was 167 (173.5) min, sleep efficiency (SE) was 62.9 (63) %, sleep latency (SL) was 6 (32) min, REM sleep was 2.85 (7.2) %, and REM first episode latency was 210.5 (196.5) minutes. The medians of the stages N1 NREM were 4.65 (15) %, N2 NREM 68.4 (29.9) %, and N3 NREM 21.8 (35.5) %. MSLT mean latency was 7.7 (12.6) minutes. A significant negative correlation exists between H/O CSF concentrations and the stage N1 NREM (rs = -0.612, p = 0.02), and the proportion of cumulative sleep time with oxygen saturation below 90 % in total sleep time (TST) t90 (rs = -0.57, p = 0.03). MSLT had significant negative correlation with TST (rs = -0.5369, p = 0.0478), with SE (rs = -0.5897, p = 0.0265), with apnea-hypopnea index (rs = -0.7631, p = 0.0002) and with deoxygenation index (rs = -0.8009, p = 0.0006). A positive correlation exists between MSLT and SL (rs = 0.6284, p = 0.0161) and between ESS and t90 (rs = 0.9014, p = 0.0004). The correlation between H/O CSF concentrations and EDS, cognitive performance, and ADL was not proved. CONCLUSIONS: Patients after NCSE exhibited sleep impairment and excessive daytime sleepiness. Hypocretin-1/orexin-A concentrations decreased only in 20 % of these cases.
- MeSH
- kohortové studie MeSH
- lidé středního věku MeSH
- lidé MeSH
- magnetická rezonanční tomografie MeSH
- orexiny * mozkomíšní mok MeSH
- polysomnografie * MeSH
- poruchy nadměrné spavosti * mozkomíšní mok MeSH
- průřezové studie MeSH
- senioři MeSH
- spánek fyziologie MeSH
- status epilepticus * mozkomíšní mok MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: There are limited data available on regional differences in the diagnosis and management of narcolepsy. In order to better understand worldwide trends in clinical assessment and management of narcolepsy, a survey of health-care providers was conducted by the World Sleep Society Narcolepsy task force. METHODS: A total of 146 surveys that included items on the diagnosis and management of narcolepsy were completed by practitioners representing 37 countries. RESULTS: Most of the participants were from Europe, North America, Oceania, Asia and Latin America. A consistent approach to applying the diagnostic criteria of Narcolepsy was documented with the exception of measurement of CSF hypocretin-1, which has limited availability. While the majority of practitioners (58%) reported not using the test, 1% indicated always evaluating CSF hypocretin-1 levels. There was much variability in the availability of currently recommended medications such as sodium oxybate and pitolisant; modafinil and antidepressants were the most commonly used medications. Amphetamines were unavailable in some countries. CONCLUSION: The results of the study highlight clinical and therapeutic realities confronted by worldwide physicians in the management of narcolepsy. While the diagnostic criteria of narcolepsy rely in part on the quantification of CSF hypocretin-1, few physicians reported having incorporated this test into their routine assessment of the condition. Regional differences in the management of narcolepsy appeared to be related to geographic availability and expense of the therapeutic agents.
- MeSH
- lidé MeSH
- narkolepsie * diagnóza farmakoterapie MeSH
- orexiny MeSH
- péče o pacienta MeSH
- polysomnografie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Asie MeSH
- Evropa MeSH
- Severní Amerika MeSH
