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Sleep is integral to life 1 . Although insufficient or disrupted sleep increases the risk of multiple pathological conditions, including cardiovascular disease 2 , we know little about the cellular and molecular mechanisms by which sleep maintains cardiovascular health. Here we report that sleep regulates haematopoiesis and protects against atherosclerosis in mice. We show that mice subjected to sleep fragmentation produce more Ly-6C high monocytes, develop larger atherosclerotic lesions and produce less hypocretin—a stimulatory and wake-promoting neuropeptide—in the lateral hypothalamus. Hypocretin controls myelopoiesis by restricting the production of CSF1 by hypocretin-receptor-expressing pre-neutrophils in the bone marrow. Whereas hypocretin-null and haematopoietic hypocretin-receptor-null mice develop monocytosis and accelerated atherosclerosis, sleep-fragmented mice with either haematopoietic CSF1 deficiency or hypocretin supplementation have reduced numbers of circulating monocytes and smaller atherosclerotic lesions. Together, these results identify a neuro-immune axis that links sleep to haematopoiesis and atherosclerosis. The fragmentation of sleep in Apoe −/− mice induces monocytosis and accelerated atherosclerosis due to a reduction in hypocretin that otherwise restricts bone marrow CSF1 availability.

Background Cerebral aneurysms (CAs) are pathological dilations of intracranial arteries with high rupture risk, yet the molecular mechanisms driving their formation remain incompletely understood. The Orexin B/OX2R system, known for regulating arousal and metabolism, has recently been implicated in vascular pathology, but its role in CAs has not been explored. Methods Serum Orexin A and B levels were measured in 38 CA patients and 43 healthy controls. A murine CA model (elastase‐induced) was established using wild‐type (WT) and OX2R knockout (OX2R−/−) mice, with or without Orexin B treatment (30 μg/kg/day for 7 weeks). Aneurysm size, inflammatory mediators (IL‐6, MMP‐9, MCP‐1, E‐selectin), macrophage infiltration (CD68), and SP‐1 expression were assessed. In vitro studies using human brain microvascular endothelial cells (HBMVECs) examined Ang II‐induced OX2R suppression, monocyte adhesion, and SP‐1‐mediated signaling following Orexin B treatment and SP‐1 overexpression. Results CA patients and mice exhibited significantly reduced serum Orexin B levels (CA patients: 3.21 ± 0.52 vs. controls: 8.56 ± 1.23 pg/mL, p < 0.01), with no change in Orexin A. OX2R expression was downregulated in the circle of Willis of CA mice. Orexin B administration attenuated aneurysm formation in WT mice (size reduction from 3.72 ± 0.469 mm to 1.93 ± 0.252 mm, p < 0.01) but not in OX2R−/− mice. Orexin B suppressed IL‐6, MMP‐9, MCP‐1, and E‐selectin expression, reduced CD68+ macrophage infiltration, and decreased SP‐1 levels in WT but not OX2R−/− mice. In HBMVECs, Ang II dose‐dependently reduced OX2R expression. Orexin B inhibited Ang II‐induced monocyte adhesion and SP‐1‐mediated pro‐inflammatory signaling, effects abolished by OX2R siRNA or SP‐1 overexpression. Conclusions The Orexin B/OX2R axis is dysregulated in CAs, and Orexin B protects against CA formation through OX2R‐dependent anti‐inflammatory mechanisms involving SP‐1 suppression. These findings identify the Orexin B/OX2R/SP‐1 pathway as a potential therapeutic target for cerebral aneurysms. Orexin B/OX2R signaling attenuates cerebral aneurysm formation by suppressing SP‐1‐mediated inflammation, macrophage infiltration, and endothelial adhesion, with OX2R knockdown abolishing these protective effects. The study highlights Orexin B as a therapeutic candidate targeting vascular inflammation and remodeling in aneurysms.

Orexin signaling in the ventral tegmental area and substantia nigra promotes locomotion and reward processing, but it is not clear whether dopaminergic neurons directly mediate these effects. We show that dopaminergic neurons in these areas mainly express orexin receptor subtype 1 (Ox1R). In contrast, only a minor population in the medial ventral tegmental area express orexin receptor subtype 2 (Ox2R). To analyze the functional role of Ox1R signaling in dopaminergic neurons, we deleted Ox1R specifically in dopamine transporter-expressing neurons of mice and investigated the functional consequences. Deletion of Ox1R increased locomotor activity and exploration during exposure to novel environments or when intracerebroventricularely injected with orexin A. Spontaneous activity in home cages, anxiety, reward processing, and energy metabolism did not change. Positron emission tomography imaging revealed that Ox1R signaling in dopaminergic neurons affected distinct neural circuits depending on the stimulation mode. In line with an increase of neural activity in the lateral paragigantocellular nucleus (LPGi) of Ox1R ΔDAT mice, we found that dopaminergic projections innervate the LPGi in regions where the inhibitory dopamine receptor subtype D2 but not the excitatory D1 subtype resides. These data suggest a crucial regulatory role of Ox1R signaling in dopaminergic neurons in novelty-induced locomotion and exploration.

Cell-surface CD200 expression by mouse EMT6 breast tumor cells increased primary tumor growth and metastasis to the draining lymph nodes (DLN) in normal (WT) BALB/c female recipients, while lack of CD200R1 expression in a CD200R1-/- host negated this effect. Silencing CD200 expression in EMT6siCD200 tumor cells also reduced their ability to grow and metastasize in WT animals. The cellular mechanisms responsible for these effects have not been studied in detail. We report characterization of tumor infiltrating (TILs) and draining lymph node (DLN) cells in WT and CD200-/- BALB/c mice, receiving WT tumor cells, or EMT6 lacking CD200 expression (EMT6siCD200 cells). Our data show an important correlation with augmented CD8+ cytotoxic T cells and resistance to tumor growth in mice lacking exposure (on either host cells or tumor) to the immunoregulatory molecule CD200. Confirmation of the importance of such CD8+ cells came from monitoring tumor growth and characterization of the TILs and DLN cells in WT mice challenged with EMT6 and EMT6siCD200 tumors and treated with CD8 and CD4 depleting antibodies. Finally, we have assessed the mechanisms(s) whereby addition of metformin as an augmenting chemotherapeutic agent in CD200-/- animals given EMT6 tumors and treated with a previously established immunotherapy regime can increase host resistance. Our data support the hypothesis that increased autophagy in the presence of metformin increases CD8+ responses and tumor resistance, an effect attenuated by the autophagy inhibitor verteporfin.

We have compared cure from local/metastatic tumor growth in BALB/c mice receiving EMT6 or the poorly immunogenic, highly metastatic 4THM, breast cancer cells following manipulation of immunosuppressive CD200:CD200R interactions or conventional chemotherapy. We reported previously that EMT6 tumors are cured in CD200R1KO mice following surgical resection and immunization with irradiated EMT6 cells and CpG oligodeoxynucleotide (CpG), while wild-type (WT) animals developed pulmonary and liver metastases within 30 days of surgery. We report growth and metastasis of both EMT6 and a highly metastatic 4THM tumor in WT mice receiving iv infusions of Fab anti-CD200R1 along with CpG/tumor cell immunization. Metastasis was followed both macroscopically (lung/liver nodules) and microscopically by cloning tumor cells at limiting dilution in vitro from draining lymph nodes (DLN) harvested at surgery. We compared these results with local/metastatic tumor growth in mice receiving 4 courses of combination treatment with anti-VEGF and paclitaxel. In WT mice receiving Fab anti-CD200R, no tumor cells are detectable following immunotherapy, and CD4+ cells produced increased TNFα/IL-2/IFNγ on stimulation with EMT6 in vitro. No long-term cure was seen following surgery/immunotherapy of 4THM, with both microscopic (tumors in DLN at limiting dilution) and macroscopic metastases present within 14 d of surgery. Chemotherapy attenuated growth/metastases in 4THM tumor-bearers and produced a decline in lung/liver metastases, with no detectable DLN metastases in EMT6 tumor-bearing mice-these latter mice nevertheless showed no significantly increased cytokine production after restimulation with EMT6 in vitro. EMT6 mice receiving immunotherapy were resistant to subsequent re-challenge with EMT6 tumor cells, but not those receiving curative chemotherapy. Anti-CD4 treatment caused tumor recurrence after immunotherapy, but produced no apparent effect in either EMT6 or 4THM tumor bearers after chemotherapy treatment. Immunotherapy, but not chemotherapy, enhances CD4+ immunity and affords long-term control of breast cancer growth and resistance to new tumor foci.

Purpose We investigated whether miRNAs in exosomes from EMT6 or 4THM tumor-bearing mice played a role in regulating inflammatory cytokine expression and/or metastasis in WT mice injected with EMT6 and/or 4THM tumor cells. Methods EMT6 tumors in BALB/c CD200R1KO mice resolve following surgical resection of localized tumor and immunization with irradiated EMT6 cells along with CpG as adjuvant. Wild-type (WT) animals treated in the same fashion develop pulmonary and liver metastases within 20 days of surgery. DLNs from CD200R1KO mice contain no tumor cells detectable at limiting dilution. In contrast, 4THM tumor cells injected into CD200R1KO show increased metastasis compared with WT mice. Transfer of serum exosomes from 4THM tumor-bearing mice to WT animals increased metastasis of EMT6 tumors, an effect attenuated by anti-IL-6 antibody. We compared miRNA expression in exosomes from the serum of 4THM/EMT6 WT or CD200R1KO tumor-bearing mice, and the effects of antagomirs to miRNAs on tumor growth. Results Complex changes in miRNA expression were observed in the isolated exosomes. Some miRNAs, including miR155, have been reported to potentiate inflammatory responses and augment inflammatory cytokine expression. Expression of miR155 increased in exosomes from 4THM relative to EMT6 tumor bearers, and antagomirs to miR155 attenuated tumor growth and metastasis, and improved survival, following infusion into WT mice. Antagomirs to the miR205 family were thought to affect metastasis by targeting epithelial-to-mesenchymal transition (EMT), increased growth and metastasis in both 4THM and EMT6 tumor-bearing mice, and decreased survival, with some modulation of inflammatory cytokine production. Conclusions Multiple pathways are implicated in differential metastasis of EMT6/4THM, and targeting these may have clinical utility in human breast cancer.

Narcolepsy type 1 is caused by severe loss or lack of brain orexin neuropeptides. We conducted a phase 2, randomized, placebo-controlled trial of TAK-994, an oral orexin receptor 2-selective agonist, in patients with narcolepsy type 1. Patients with confirmed narcolepsy type 1 according to clinical criteria were randomly assigned to receive twice-daily oral TAK-994 (30 mg, 90 mg, or 180 mg) or placebo. The primary end point was the mean change from baseline to week 8 in average sleep latency (the time it takes to fall asleep) on the Maintenance of Wakefulness Test (range, 0 to 40 minutes; normal ability to stay awake, ≥20 minutes). Secondary end points included the change in the Epworth Sleepiness Scale (ESS) score (range, 0 to 24, with higher scores indicating greater daytime sleepiness; normal, <10) and the weekly cataplexy rate. Of the 73 patients, 17 received TAK-994 at a dose of 30 mg twice daily, 20 received 90 mg twice daily, 19 received 180 mg twice daily, and 17 received placebo. The phase 2 trial and an extension trial were terminated early owing to hepatic adverse events. Primary end-point data were available for 41 patients (56%); the main reason for missing data was early trial termination. Least-squares mean changes to week 8 in average sleep latency on the MWT were 23.9 minutes in the 30-mg group, 27.4 minutes in the 90-mg group, 32.6 minutes in the 180-mg group, and -2.5 minutes in the placebo group (difference vs. placebo, 26.4 minutes in the 30-mg group, 29.9 minutes in the 90-mg group, and 35.0 minutes the 180-mg group; P<0.001 for all comparisons). Least-squares mean changes to week 8 in the ESS score were -12.2 in the 30-mg group, -13.5 in the 90-mg group, -15.1 in the 180-mg group, and -2.1 in the placebo group (difference vs. placebo, -10.1 in the 30-mg group, -11.4 in the 90-mg group, and -13.0 in the 180-mg group). Weekly incidences of cataplexy at week 8 were 0.27 in the 30-mg group, 1.14 in the 90-mg group, 0.88 in the 180-mg group, and 5.83 in the placebo group (rate ratio vs. placebo, 0.05 in the 30-mg group, 0.20 in the 90-mg group, and 0.15 in the 180-mg group). A total of 44 of 56 patients (79%) receiving TAK-994 had adverse events, most commonly urinary urgency or frequency. Clinically important elevations in liver-enzyme levels occurred in 5 patients, and drug-induced liver injury meeting Hy's law criteria occurred in 3 patients. In a phase 2 trial involving patients with narcolepsy type 1, an orexin receptor 2 agonist resulted in greater improvements on measures of sleepiness and cataplexy than placebo over a period of 8 weeks but was associated with hepatotoxic effects. (Funded by Takeda Development Center Americas; TAK-994-1501 and TAK-994-1504 ClinicalTrials.gov numbers, NCT04096560 and NCT04820842.).

Sleepers awake A paper published in Nature in April raised the intriguing possibility that optical therapies might be developed to treat neurological disorders. That work, in tissue slices and in C. elegans roundworms, showed that brain cells can be genetically engineered to alter their activity in response to pulses of different colours of light. A follow-up study now shows that behaviour can be modified in a living mammal by similar means. Hypocretin (Hcrt)-producing neurons in the hypothalamus are active during transitions from sleep to waking states. Optical stimulation of mouse Hcrt neurons engineered to respond to light increases the likelihood of transition from sleep to wakefulness, with higher frequencies causing more abrupt awakening. As Hcrt deficiency is linked to narcolepsy, these results may provide insights into sleep disorders. The neural underpinnings of sleep involve interactions between sleep-promoting areas such as the anterior hypothalamus, and arousal systems located in the posterior hypothalamus, the basal forebrain and the brainstem 1 , 2 . Hypocretin 3 (Hcrt, also known as orexin 4 )-producing neurons in the lateral hypothalamus 5 are important for arousal stability 2 , and loss of Hcrt function has been linked to narcolepsy 6 , 7 , 8 , 9 . However, it is unknown whether electrical activity arising from Hcrt neurons is sufficient to drive awakening from sleep states or is simply correlated with it. Here we directly probed the impact of Hcrt neuron activity on sleep state transitions with in vivo neural photostimulation 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , genetically targeting channelrhodopsin-2 to Hcrt cells and using an optical fibre to deliver light deep in the brain, directly into the lateral hypothalamus, of freely moving mice. We found that direct, selective, optogenetic photostimulation of Hcrt neurons increased the probability of transition to wakefulness from either slow wave sleep or rapid eye movement sleep. Notably, photostimulation using 5–30 Hz light pulse trains reduced latency to wakefulness, whereas 1 Hz trains did not. This study establishes a causal relationship between frequency-dependent activity of a genetically defined neural cell type and a specific mammalian behaviour central to clinical conditions and neurobehavioural physiology.

Introduction Narcolepsy Type 1 (NT1) is a chronic neurological disorder characterized by excessive daytime sleepiness (EDS), cataplexy, and REM intrusions, caused by a deficiency of orexin (hypocretin), a hypothalamic neuropeptide essential for arousal, REM sleep regulation, metabolism, and emotional stability. This review synthesizes and critically analyzes the pathophysiological, clinical, and therapeutic dimensions of orexin deficiency in narcolepsy, with particular emphasis on recent advances from 2023 to 2025. Methods This narrative analytical review analyzed 50 peer‐reviewed publications covering the neurobiology of the orexin system, diagnostic evolution of NT1, comparative symptomatology of central hypersomnia disorders, and recent therapeutic innovations. Out of which 16 studies were selected based on relevance, recency, and translational impact. Results Recent research confirms that over 90% of NT1 patients exhibit cerebrospinal fluid (CSF) orexin‐A levels below 110 pg/mL and carry the HLA‐DQB1*06:02 allele, indicating a strong genetic and immunological association. Postmortem analyses have revealed a loss of up to 95% of orexin‐producing neurons in the lateral hypothalamus. In a 2024 multicenter trial, danavorexton (a selective orexin receptor‐2 [OX2R] agonist) was associated with a mean improvement of 11.1 points on the Maintenance of Wakefulness Test, outperforming modafinil and suggesting the feasibility of receptor‐level restoration. In addition, intermediate orexin levels (110–200 pg/mL) have been documented in a subset of patients with narcolepsy Type 2 (NT2) and idiopathic hypersomnia (IH), challenging the binary diagnostic threshold and prompting reevaluation of orexin's diagnostic role. Orexin dysfunction has also been correlated with high psychiatric comorbidity rates, including major depressive disorder in 40% and anxiety disorders in nearly 30% of NT1 patients. These manifestations reflect orexin's broader role in regulating REM sleep, metabolic processes, and autonomic stability. Conclusion Orexin deficiency remains the central mechanism underlying NT1, with far‐reaching implications in psychiatric and neurodegenerative disease. While emerging orexin‐targeted therapies offer promising disease‐modifying potential, critical challenges persist in standardizing biomarkers, resolving NT2 classification ambiguities, and ensuring global access to therapeutics. Orexin deficiency drives narcolepsy Type 1, leading to excessive daytime sleepiness, cataplexy, and REM intrusions. This review highlights recent advances (2023–2025) in molecular mechanisms, diagnostics, and emerging orexin‐targeted therapies with the potential for disease modification.

The peptide hormone ghrelin has previously been linked to the regulation of metabolism. This study in mice finds that increasing levels of ghrelin, either through subcutaneous injections or calorie restriction, has an anxiolytic and antidepressive effect. This reveals a previously unknown function for ghrelin. We found that increasing ghrelin levels, through subcutaneous injections or calorie restriction, produced anxiolytic- and antidepressant-like responses in the elevated plus maze and forced swim test. Moreover, chronic social defeat stress, a rodent model of depression, persistently increased ghrelin levels, whereas growth hormone secretagogue receptor ( Ghsr ) null mice showed increased deleterious effects of chronic defeat. Together, these findings demonstrate a previously unknown function for ghrelin in defending against depressive-like symptoms of chronic stress.