In vivo photocontrol of orexin receptors with a nanomolar light-regulated analogue of orexin-B.

Orexinergic neurons are critically involved in regulating arousal, wakefulness, and appetite. Their dysfunction has been associated with sleeping disorders, and non-peptide drugs are currently being developed to treat insomnia and narcolepsy. Yet, no light-regulated agents are available to reversibly control their activity. To meet this need, a photoswitchable peptide analogue of the endogenous neuroexcitatory peptide orexin-B was designed, synthesized, and tested in vitro and in vivo. This compound - photorexin - is the first photo-reversible ligand reported for orexin receptors. It allows dynamic control of activity in vitro (including almost the same efficacy as orexin-B, high nanomolar potency, and subtype selectivity to human OX2 receptors) and in vivo in zebrafish larvae by direct application in water. Photorexin induces dose- and light-dependent changes in locomotion and a reduction in the successive induction reflex that is associated with sleep behavior. Molecular dynamics calculations indicate that trans and cis photorexin adopt similar bent conformations and that the only discriminant between their structures and activities is the positioning of the N-terminus. This, in the case of the more active trans isomer, points towards the OX2 N-terminus and extra-cellular loop 2, a region of the receptor known to be involved in ligand binding and recognition consistent with a "message-address" system. Thus, our approach could be extended to several important families of endogenous peptides, such as endothelins, nociceptin, and dynorphins among others, that bind to their cognate receptors through a similar mechanism: a "message" domain involved in receptor activation and signal transduction, and an "address" sequence for receptor occupation and improved binding affinity.

Sleep quality in patients with chronic spontaneous urticaria and relation with Orexin-A, leptin, and ghrelin.

Background: Sleep can be affected in patients with chronic spontaneous urticaria (CSU). The mechanisms of sleep regulation remain poorly understood. Orexin-A, a neuroexcitatory peptide, plays a role in coordinating sleep-wake states. Ghrelin and leptin are involved in sleep regulation through the orexin system. Objective: The effects of orexin-A, ghrelin, and leptin on sleep quality in patients with CSU have not been investigated. We aimed to determine the effects of CSU on sleep quality and the association between serum orexin-A, ghrelin, and leptin levels, and sleep quality in patients with CSU. Methods: Thirty-three patients with CSU and 34 sex- and age-matched controls were included in the study. Serum orexin-A, leptin, and ghrelin levels, and the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS) scores were measured in patients with CSU and in the controls; also used were the chronic urticaria quality-of-life questionnaire score and the urticaria activity score used for 7 consecutive days. Results: Median (minimum-maximum) orexin-A, leptin, and ghrelin levels in patients were 385 pg/mL (90-495 pg/mL), 3.1 ng/mL (0-21.2 ng/mL), and 701.8 pg/mL (101.9-827.7 pg/mL), respectively. Median serum orexin-A and leptin levels were higher in the patients compared with the controls (p < 0.001 and p = 0.012, respectively), whereas the median serum ghrelin levels were similar to the controls (p = 0.616). The serum orexin-A level was positively correlated with ghrelin (r = 0.298, p = 0.014), PSQI sleep quality (r = 0.356, p = 0.003), and ESS (r = 0.357, p = 0.003). Conclusion: Serum orexin-A is associated with sleep quality in patients with CSU. Further studies are needed to elucidate the role of ghrelin and leptin on sleep quality in patients with CSU.

Astrocytic metabolic control of orexinergic activity in the lateral hypothalamus regulates sleep and wake architecture.

Neuronal activity undergoes significant changes during vigilance states, accompanied by an accommodation of energy demands. While the astrocyte-neuron lactate shuttle has shown that lactate is the primary energy substrate for sustaining neuronal activity in multiple brain regions, its role in regulating sleep/wake architecture is not fully understood. Here we investigated the involvement of astrocytic lactate supply in maintaining consolidated wakefulness by downregulating, in a cell-specific manner, the expression of monocarboxylate transporters (MCTs) in the lateral hypothalamus of transgenic mice. Our results demonstrate that reduced expression of MCT4 in astrocytes disrupts lactate supply to wake-promoting orexin neurons, impairing wakefulness stability. Additionally, we show that MCT2-mediated lactate uptake is necessary for maintaining tonic firing of orexin neurons and stabilizing wakefulness. Our findings provide both in vivo and in vitro evidence supporting the role of astrocyte-to-orexinergic neuron lactate shuttle in regulating proper sleep/wake stability.

Neurochemical and genetic factors in panic disorder: a systematic review.

This systematic review addresses the complex nature of Panic Disorder (PD), characterized by recurrent episodes of acute fear, with a focus on updating and consolidating knowledge regarding neurochemical, genetic, and epigenetic factors associated with PD. Utilizing the PRISMA methodology, 33 original peer-reviewed studies were identified, comprising 6 studies related to human neurochemicals, 10 related to human genetic or epigenetic alterations, and 17 animal studies. The review reveals patterns of altered expression in various biological systems, including neurotransmission, the Hypothalamic-Pituitary-Adrenal (HPA) axis, neuroplasticity, and genetic and epigenetic factors leading to neuroanatomical modifications. Noteworthy findings include lower receptor binding of GABAA and serotonin neurotransmitters in the amygdala. The involvement of orexin (ORX) neurons in the dorsomedial/perifornical region in triggering panic reactions is highlighted, with systemic ORX-1 receptor antagonists blocking panic responses. Elevated Interleukin 6 and leptin levels in PD patients suggest potential connections between stress-induced inflammatory changes and PD. Brain-derived neurotrophic factor (BDNF) and tyrosine receptor kinase B (TrkB) signaling are implicated in panic-like responses, particularly in the dorsal periaqueductal gray (dPAG), where BDNF's panicolytic-like effects operate through GABAA-dependent mechanisms. GABAergic neurons' inhibitory influence on dorsomedial and posterior hypothalamus nuclei is identified, potentially reducing the excitability of neurons involved in panic-like responses. The dorsomedial hypothalamus (DMH) is highlighted as a specific hypothalamic nucleus relevant to the genesis and maintenance of panic disorder. Altered brain lactate and glutamate concentrations, along with identified genetic polymorphisms linked to PD, further contribute to the intricate neurochemical landscape associated with the disorder. The review underscores the potential impact of neurochemical, genetic, and epigenetic factors on the development and expression of PD. The comprehensive insights provided by this systematic review contribute to advancing our understanding of the multifaceted nature of Panic Disorder and pave the way for targeted therapeutic strategies.

From past to future: 50 years of pharmacological interventions to treat narcolepsy.

The history of narcolepsy research began with the pioneering work of Jean-Baptiste-Édouard Gélineau in the late 19th century. In the 1880s, Gélineau introduced the term "narcolepsy" to describe a condition characterized by sudden and uncontrollable episodes of sleep. His clinical descriptions laid the foundation for our understanding of this complex disorder. Over the last half-century, the pharmacological landscape for narcolepsy treatment has evolved remarkably, shifting from merely managing symptoms to increasingly targeting its underlying pathophysiology. By the 1930s, treatments such as ephedrine and amphetamine were introduced to alleviate excessive daytime sleepiness, marking significant advancements in narcolepsy management. These stimulants provided temporary relief, helping patients maintain wakefulness during the day. As research progressed, the focus shifted towards understanding the disorder's underlying mechanisms. The discovery of orexin (also known as hypocretin) in the late 1990s revolutionized the field. This breakthrough underscored the importance of orexin in regulating sleep-wake cycles and provided new targets for pharmacological intervention. Looking ahead, the future of narcolepsy pharmacotherapy is poised for further innovation. The ongoing exploration of orexin receptor agonists and the potential development of neuroprotective therapeutic targets underscore a promising horizon. Emerging research into the genetic and immunological underpinnings of narcolepsy opens new avenues for personalized medicine approaches and the identification of biomarkers for more precise treatment strategies. Additionally, the refinement of existing treatments through improved delivery systems and the investigation of combination therapies offer opportunities for enhanced efficacy and improved quality of life for patients with narcolepsy.

The value of using ELISA to detect orexin-A in cerebrospinal fluid in the diagnosis of narcolepsy.

Orexin in cerebrospinal fluid (CSF) is a neuropeptide synthesized by a cluster of neurons in the lateral hypothalamus. It mainly functions to maintain arousal, regulate feeding, and participate in reward mechanisms. Radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) can detect CSF orexin. At present, RIA is widely used but is limited by various conditions, which is not conducive to its widespread development. We aimed to determine whether ELISA can replace RIA in detecting orexin in CSF. We investigated the results of 20 patients with central disorders of hypersomnolence, including 11 with narcolepsy type 1, 2 with narcolepsy type 2, 5 with idiopathic hypersomnia, and 2 with other causes of somnolence. RIA and ELISA were used to detect CSF orexin, and P values <.05 were considered to be significant. In the narcolepsy and non-narcolepsy type 1 groups, there was no correlation between the RIA and ELISA results (P > .05). In the narcolepsy type 1 group, the ELISA and RIA results were significantly different (P < .05), but this was not observed in the non-narcolepsy type 1 group (P > .05). The accuracy of ELISA to detect CSF orexin was lower than that of RIA (P < .05). ELISA cannot replace RIA in the measurement of CSF orexin, and RIA is recommended as the first choice when narcolepsy is suspected.

The protective effects of orexin-A in alleviating cell senescence against interleukin-1ß (IL-1ß) in chondrocytes.

Osteoarthritis (OA) is one of the most important causes of global disability, and dysfunction of chondrocytes is an important risk factor. The treatment of OA is still a challenge. Orexin-A is a hypothalamic peptide, and its effects in OA are unknown. In this study, we found that exposure to interleukin-1ß (IL-1ß) reduced the expression of orexin-2R, the receptor of orexin-A in TC-28a2 chondrocytes. Importantly, the senescence-associated ß-galactosidase (SA-ß-gal) staining assay demonstrated that orexin-A treatment ameliorates IL-1ß-induced cellular senescence. Importantly, the presence of IL-1ß significantly reduced the telomerase activity of TC-28a2 chondrocytes, which was rescued by orexin-A. We also found that orexin-A prevented IL-1ß-induced increase in the levels of Acetyl-p53 and the expression of p21. It is shown that orexin-A mitigates IL-1ß-induced reduction of sirtuin 3 (SIRT3). Silencing of SIRT3 abolished the protective effects of orexin-A against IL-1ß-induced cellular senescence. These results imply that orexin-A might serve as a promising therapeutic agent for OA.

The allatotropin/orexin system as an example of immunomodulatory properties of neuropeptides.

The central nervous system (CNS) plays a critical role in signal integration in animals and allows the orchestration of life processes to maintain homeostasis. Current research clearly shows that inflammatory processes can also be modulated by the CNS via the neuroendocrine system. One of the neuropeptide families that participate in vertebrates in this process is orexins (OXs). Interestingly, our previous results suggested that a similar dependency may also exist between neuropeptides and immune system activity in insects. Due to the structural homology of orexin and allatotropin receptors and the functional similarity between these two neuropeptide families, the main aim of this research was to perform a complex analysis of the relationships between allatotropin (AT) and the insect immune response. Our results revealed functional similarities between vertebrate OXs and insect ATs. Similar effects were observed in the profile of the expression level of the gene encoding the AT precursor in the Tenebrio molitor nervous system and in the general action of Tenmo-AT on selected immune parameters of the tested beetles. Moreover, for the first time in insects, we confirmed the role of cytokines in the modulation of neuroendocrine system by determining the effect of Spätzle-like protein injection on the expression of genes encoding AT precursor and receptor. All these results are important for understanding the evolutionary basis of hormonal regulation of the immune response.

Increased Expression of Orexin-A in Patients Affected by Polycystic Kidney Disease.

Orexin-A is a neuropeptide product of the lateral hypothalamus that acts on two receptors, OX1R and OX2R. The orexinergic system is involved in feeding, sleep, and pressure regulation. Recently, orexin-A levels have been found to be negatively correlated with renal function. Here, we analyzed orexin-A levels as well as the incidence of SNPs in the hypocretin neuropeptide precursor (HCRT) and its receptors, HCRTR1 and HCRTR2, in 64 patients affected by autosomal dominant polycystic kidney disease (ADPKD) bearing truncating mutations in the PKD1 or PKD2 genes. Twenty-four healthy volunteers constituted the control group. Serum orexin-A was assessed by ELISA, while the SNPs were investigated through Sanger sequencing. Correlations with the main clinical features of PKD patients were assessed. PKD patients showed impaired renal function (mean eGFR 67.8 ± 34.53) and a statistically higher systolic blood pressure compared with the control group (p < 0.001). Additionally, orexin-A levels in PKD patients were statistically higher than those in healthy controls (477.07 ± 69.42 pg/mL vs. 321.49 ± 78.01 pg/mL; p < 0.001). Furthermore, orexin-A inversely correlated with blood pressure (p = 0.0085), while a direct correlation with eGFR in PKD patients was found. None of the analyzed SNPs showed any association with orexin-A levels in PKD. In conclusion, our data highlights the emerging role of orexin-A in renal physiology and its potential relevance to PKD. Further research is essential to elucidate the intricate mechanisms underlying orexin-A signaling in renal function and its therapeutic implications for PKD and associated cardiovascular complications.

Graph convolutional network with attention mechanism improve major depressive depression diagnosis based on plasma biomarkers and neuroimaging data.

BACKGROUND: The absence of clinically-validated biomarkers or objective protocols hinders effective major depressive disorder (MDD) diagnosis. Compared to healthy control (HC), MDD exhibits anomalies in plasma protein levels and neuroimaging presentations. Despite extensive machine learning studies in psychiatric diagnosis, a reliable tool integrating multi-modality data is still lacking. METHODS: In this study, blood samples from 100 MDD and 100 HC were analyzed, along with MRI images from 46 MDD and 49 HC. Here, we devised a novel algorithm, integrating graph neural networks and attention modules, for MDD diagnosis based on inflammatory cytokines, neurotrophic factors, and Orexin A levels in the blood samples. Model performance was assessed via accuracy and F1 value in 3-fold cross-validation, comparing with 9 traditional algorithms. We then applied our algorithm to a dataset containing both the aforementioned protein quantifications and neuroimages, evaluating if integrating neuroimages into the model improves performance. RESULTS: Compared to HC, MDD showed significant alterations in plasma protein levels and gray matter volume revealed by MRI. Our new algorithm exhibited superior performance, achieving an F1 value and accuracy of 0.9436 and 94.08 %, respectively. Integration of neuroimaging data enhanced our novel algorithm's performance, resulting in an improved F1 value and accuracy, reaching 0.9543 and 95.06 %. LIMITATIONS: This single-center study with a small sample size requires future evaluations on a larger test set for improved reliability. CONCLUSIONS: In comparison to traditional machine learning models, our newly developed MDD diagnostic model exhibited superior performance and showed promising potential for inclusion in routine clinical diagnosis for MDD.

Control of motivation for sucrose in the paraventricular hypothalamic nucleus by dynorphin peptides and the kappa opioid receptor.

The dynorphin peptides are the endogenous ligands for the kappa opioid receptor (KOR) and regulate food intake. Administration of dynorphin-A1-13 (DYN) in the paraventricular hypothalamic nucleus (PVN) increases palatable food intake, and this effect is blocked by co-administration of the orexin-A neuropeptide, which is co-released with DYN in PVN from neurons located in the lateral hypothalamus. While PVN administration of DYN increases palatable food intake, whether it increases food-seeking behaviors has yet to be examined. We tested the effects of DYN and norBNI (a KOR antagonist) on the seeking and consumption of sucrose using a progressive ratio (PR) and demand curve (DC) tasks. In PVN, DYN did not alter the sucrose breaking point (BP) in the PR task nor the elasticity or intensity of demand for sucrose in the DC task. Still, DYN reduced the delay in obtaining sucrose and increased licks during sucrose intake in the PR task, irrespective of the co-administration of orexin-A. In PVN, norBNI increased the delay in obtaining sucrose and reduced licks during sucrose intake in the PR task while increasing elasticity without altering intensity of demand in the DC task. However, subcutaneous norBNI reduced the BP for sucrose and increased the delay in obtaining sucrose in the PR task while reducing the elasticity of demand. Together, these data show different effects of systemic and PVN blockade of KOR on food-seeking, consummatory behaviors, and incentive motivation for sucrose and suggest that KOR activity in PVN is necessary but not sufficient to drive seeking behaviors for palatable food.

Trigeminal nerve electrical stimulation attenuates early traumatic brain injury through the TLR4/NF-κB/NLRP3 signaling pathway mediated by orexin-A/OX1R system.

BACKGROUND: Traumatic brain injury (TBI) is a significant contributor to global mortality and disability, and emerging evidence indicates that trigeminal nerve electrical stimulation (TNS) is a promising therapeutic intervention for neurological impairment following TBI. However, the precise mechanisms underlying the neuroprotective effects of TNS in TBI are poorly understood. Thus, the objective of this study was to investigate the potential involvement of the orexin-A (OX-A)/orexin receptor 1 (OX1R) mediated TLR4/NF-κB/NLRP3 signaling pathway in the neuroprotective effects of TNS in rats with TBI. METHODS: Sprague-Dawley rats were randomly assigned to four groups: sham, TBI, TBI+TNS+SB334867, and TBI+TNS. TBI was induced using a modified Feeney's method, and subsequent behavioral assessments were conducted to evaluate neurological function. The trigeminal nerve trunk was isolated, and TNS was administered following the establishment of the TBI model. The levels of neuroinflammation, brain tissue damage, and proteins associated with the OX1R/TLR4/NF-κB/NLRP3 signaling pathway were assessed using hematoxylin-eosin staining, Nissl staining, western blot analysis, quantitative real-time polymerase chain reaction, and immunofluorescence techniques. RESULTS: The findings of our study indicate that TNS effectively mitigated tissue damage, reduced brain edema, and alleviated neurological deficits in rats with TBI. Furthermore, TNS demonstrated the ability to attenuate neuroinflammation levels and inhibit the expression of proteins associated with the TLR4/NF-κB/NLRP3 signaling pathway. However, it is important to note that the aforementioned effects of TNS were reversible upon intracerebroventricular injection of an OX1R antagonist. CONCLUSION: TNS may prevent brain damage and relieve neurological deficits after a TBI by inhibiting inflammation, possibly via the TLR4/NF-κB/NLRP3 signaling pathway mediated by OX-A/OX1R.

Hypocretin-1/orexin-A, sleep and excessive daytime sleepiness in patients with nonconvulsive status epilepticus: A cross-sectional cohort study.

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.

Orexin neurons track temporal features of blood glucose in behaving mice.

Does the brain track how fast our blood glucose is changing? Knowing such a rate of change would enable the prediction of an upcoming state and a timelier response to this new state. Hypothalamic arousal-orchestrating hypocretin/orexin neurons (HONs) have been proposed to be glucose sensors, yet whether they track glucose concentration (proportional tracking) or rate of change (derivative tracking) is unknown. Using simultaneous recordings of HONs and blood glucose in behaving male mice, we found that maximal HON responses occur in considerable temporal anticipation (minutes) of glucose peaks due to derivative tracking. Analysis of >900 individual HONs revealed glucose tracking in most HONs (98%), with derivative and proportional trackers working in parallel, and many (65%) HONs multiplexed glucose and locomotion information. Finally, we found that HON activity is important for glucose-evoked locomotor suppression. These findings reveal a temporal dimension of brain glucose sensing and link neurobiological and algorithmic views of blood glucose perception in the brain's arousal orchestrators.

Orexin Facilitates the Peripheral Chemoreflex via Corticotropin-Releasing Hormone Neurons Projecting to the Nucleus of the Solitary Tract.

We previously showed that orexin neurons are activated by hypoxia and facilitate the peripheral chemoreflex (PCR)-mediated hypoxic ventilatory response (HVR), mostly by promoting the respiratory frequency response. Orexin neurons project to the nucleus of the solitary tract (nTS) and the paraventricular nucleus of the hypothalamus (PVN). The PVN contributes significantly to the PCR and contains nTS-projecting corticotropin-releasing hormone (CRH) neurons. We hypothesized that in male rats, orexin neurons contribute to the PCR by activating nTS-projecting CRH neurons. We used neuronal tract tracing and immunohistochemistry (IHC) to quantify the degree that hypoxia activates PVN-projecting orexin neurons. We coupled this with orexin receptor (OxR) blockade with suvorexant (Suvo, 20 mg/kg, i.p.) to assess the degree that orexin facilitates the hypoxia-induced activation of CRH neurons in the PVN, including those projecting to the nTS. In separate groups of rats, we measured the PCR following systemic orexin 1 receptor (Ox1R) blockade (SB-334867; 1 mg/kg) and specific Ox1R knockdown in PVN. OxR blockade with Suvo reduced the number of nTS and PVN neurons activated by hypoxia, including those CRH neurons projecting to nTS. Hypoxia increased the number of activated PVN-projecting orexin neurons but had no effect on the number of activated nTS-projecting orexin neurons. Global Ox1R blockade and partial Ox1R knockdown in the PVN significantly reduced the PCR. Ox1R knockdown also reduced the number of activated PVN neurons and the number of activated tyrosine hydroxylase neurons in the nTS. Our findings suggest orexin facilitates the PCR via nTS-projecting CRH neurons expressing Ox1R.

Sex-dependent effects of monomeric α-synuclein on calcium and cell death of lateral hypothalamic mouse neurons are altered by orexin.

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.

Effect of Centella asiatica ethanol extract on zebrafish larvae ( Danio rerio) insomnia model through inhibition of Orexin, ERK, Akt and p38.

Background: Insomnia is difficulty initiating or maintaining sleep for at least three nights a week or more and lasting for at least 3 months. One of the molecules that play a role in the circadian rhythm of arousal system is hypocretin/orexin. Orexin activates the p38-MAPK signaling pathway and increases phosphorylated ERK1/2 levels. Centella asiatica (CA) has a role in the signal work of the MAPK/ERK, Akt, and p38 path in many various diseases. Methods: The research method used is true laboratory experimental. The research approach used was randomized control group post-test only. Zebrafish embryos aged 0-7 dpf were used in this study. The treatment group consisted of 5 groups: normal, insomnia, insomnia + 2.5 µg/mL CA, insomnia + 5 µg/mL CA, and insomnia + 10 µg/mL CA. The locomotor motion of zebrafish larvae was observed using Basler cameras on days five-, six- and seven-day post fertilization (dpf), then analyzed by using Western Blot method. Results: The results proved that exposure to CA extract was able to reduce the expression of orexin (91963 ± 9129) and p38 (117425 ± 6398) as an arousal trigger in the sleep-wake cycle, with the most optimal concentration of CA 5 µg/mL. Exposure to CA extract was also able to reduce the expression of ERK (94795 ± 30830) and Akt (60113.5 ± 27833.5) with an optimum concentration of CA 2.5 µg/mL. Conclusion: Exposure to CA extract was able to improve the sleep activity of zebrafish larvae insomnia model by extending the total inactivity time ( cumulative duration) and shortening the duration of first sleep ( latency to first) in light and dark phases through inhibition of orexin, ERK, p38, and Akt.

Exploring the role of Orexin-A neuropeptide in Parkinson's disease: A systematic review and meta-analysis.

BACKGROUND: Parkinson's disease (PD) is a progressive neurological condition that affects movement and coordination. Orexin-A (OXA) is an excitatory neuropeptide that is found throughout the central nervous system. There is growing interest in investigating the potential diagnostic and therapeutic utility of OXA in PD. To date, studies have reported a wide range of OXA concentrations in patients with PD. In this review, we discuss the current understanding of the dysregulation of OXA in PD and analyze its levels in the CSF. METHODS: We searched six databases (PubMed, Scopus, Web of Science, EMBASE, ProQuest, and EBSCOHost) and preprint servers using a predetermined search strategy through 4th March 4, 2023. The search keywords included "Parkinson's disease", "Orexin-A", "Hypocretin-1", "cerebrospinal fluid", and "CSF". Studies that reported OXA/Hypocretin-1 levels in the CSF of patients with PD were included. Two researchers independently reviewed the records and extracted data. FINDINGS: Eighteen studies involving 244 patients were analyzed. CSF Orexin-A concentrations were lower in patients with Parkinson's disease than in controls, with a mean difference of -59.21 (95 % CI: -89.10 to -29.32). The mean OXA levels were 281.52 (95 % CI: 226.65-336.40). CONCLUSION: Our analysis reveals lower concentrations of orexin-A in the cerebrospinal fluid of Parkinson's disease patients compared to controls, but within the normal range. These findings suggest a potential, but not significant, disruption in the orexinergic system associated with the disease.

Effects of fasting and environmental factors on appetite regulators in pond loach Misgurnus anguillicaudatus.

The pond loach (Misgurnus anguillicaudatus) is an important aquaculture freshwater species, used as an ornamental fish, food source for humans and angling bait. Pond loaches are resistant to fasting and extreme environmental conditions, including temperature and low oxygen levels. Little is known about how these factors affect the feeding physiology and the endocrine regulation of feeding of loaches. In this study, we examined the effects of fasting, as well as increased temperature and decreased oxygen levels on food intake and transcript levels of appetite regulators. Fasted fish had lower blood glucose levels, and lower expression levels of intestine CCK and PYY, and brain CART1, but had higher levels of brain orexin and ghrelin than fed fish. Fish held at 30 °C had higher food intake, glucose levels, and mRNA levels of intestine CCK and PYY, and brain CART2, but lower brain orexin levels than fish at 20 °C. Fish held at low oxygen levels had a lower food intake, higher intestine CCKa and ghrelin, and brain orexin, CART2 and ghrelin mRNA expression levels than fish held at high O2 levels. Our results suggest that fasting and high temperatures increase the expression of orexigenic and anorexigenic factors respectively, whereas the increase in expression of both orexigenic and anorexigenic factors in low O2 environments might not be related to their role in feeding, but possibly to protection from tissue damage. The results of our study might shed new light on how pond loaches are able to cope with extreme environmental conditions such as low food availability, extreme temperatures and hypoxia.

Orexin B protects dopaminergic neurons from 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity associated with reduced extracellular signal-regulated kinase phosphorylation.

BACKGROUND: The loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) is a major pathological hallmark of Parkinson's disease (PD). Orexin B (OXB) has been reported to promote the growth of DA neurons. However, the roles of OXB in the degeneration of DA neurons still remained not fully clear. METHODS: An in vivo PD model was constructed by administrating 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice. Pole test was performed to investigate the motor function of mice and the number of DA neurons was detected by immunofluorescence (IF). A PD cell model was established by treating SH-SY5Y cells with 1-methyl-4-phenylpyridinium (MPP+). OXB was added to the culture medium 2 h after MPP + treatment. Microscopic analysis was carried out to investigate the function of OXB in the cell model of PD 24 h after MPP + challenge. RNA-Seq analysis of the PD cell model was performed to explore the possible mechanisms. Western blot was used to detect the phosphorylation levels of extracellular signal-regulated kinase (ERK). RESULTS: OXB significantly decreased the DA neurons death caused by MPTP, alleviated MPP+-induced neurotoxicity in SH-SY5Y cells, and robustly enhanced the weight and motor ability of PD mice. Besides, RNA-Seq analysis demonstrated that the mitogen-activated protein kinase (MAPK) pathway was involved in the pathology of PD. Furthermore, MPP + led to increased levels of phosphorylation of ERK (p-ERK), OXB treatment significantly decreased the levels of p-ERK in MPP+-treated SH-SY5Y cells. CONCLUSIONS: This study demonstrated that OXB exerts a neuroprotective role associated with reduced ERK phosphorylation in the PD model. This suggests that OXB may have therapeutic potential for treatment of PD.