Interleukin-10 inhibits spontaneous sleep in rabbits

Beta-Myrcene as a Sedative-Hypnotic Component from Lavender Essential Oil in DL-4-Chlorophenylalanine-Induced-Insomnia Mice

With the increasing prevalence of insomnia-related diseases, the effective treatment of insomnia has become an important health research topic. Lavender (Lavandula angustifolia Mill.) essential oil (LEO) is a commonly used medicine for the treatment of insomnia and neurological disorders. However, neither the active components nor its sedative-hypnotic mechanism have been fully discovered. This study aimed to screen the main active terpenes and discover the possible mechanism of LEO through network pharmacology in the treatment of insomnia-related diseases, as well as to verify our hypothesis in insomnia mice. The results showed that, in LEO's 15 potential active ingredients, beta-myrcene had strong sedative-hypnotic effects through the serotonergic synaptic pathway according to the network pharmacological prediction. Further, PCPA(DL-4-chlorophenylalanine)-induced insomnia mice were treated with beta-myrcene for one day or seven days. The quiet state of insomnia mice was increased effectively, and the hypnotic effect was enhanced by anaobarbital sodium by prolonging sleep duration, decreasing sleep latency, and increasing the rate of falling asleep. Beta-myrcene reduced the damage to hypothalamic neuron cells induced by PCPA and increased neurotransmitter levels of GABA, 5-HT, and Glu in the serum and hypothalamus of insomnia mice. Meanwhile, beta-myrcene exerted an improvement in insomnia by upregulating relevant genes and protein expression in the serotonergic synaptic pathway. These results support the merit of the sedative-hypnotic activity of LEO. Beta-myrcene, a terpene in LEO, may be the main source of its sedative-hypnotic properties. It may serve as a good potential compound in future clinical studies on coping with insomnia.

Dupilumab improves sleep quality in chronic rhinosinusitis with nasal polyps

PURPOSE

Chronic rhinosinusitis with nasal polyps (CRSwNP) often alters sleep quality. Dupilumab emerged as an innovative and effective therapy for refractory/recurrent severe CRSwNP. The aim of this observational retrospective study was to evaluate the sleep quality in patients with CRSwNP who underwent treatment with dupilumab.

MATERIALS AND METHODS

Forty-five patients treated with dupilumab for CRSwNP were enrolled. Clinical parameters (age, sex, comorbidities, Nasal Polyp Score - NPS, Asthma Control Test - ACT), nasal cytology, quality of life (Sino Nasal Outcome Test 22 - SNOT-22), sleep quality (Pittsburgh Sleep Quality Index - PSQI, Epworth Sleepiness Scale - ESS), and risk of sleep apnea (STOP-BANG) were recorded before treatment (T0), and after 3 (T1), 6 (T2), and 12 months (T3).

RESULTS

NPS, ACT and SNOT-22 total score improved during treatment (p < 0.05). Meanwhile, all sleep parameters evaluated with SNOT-22, ESS and PSQI improved over time (p < 0.001), expect for PSQI Use of sleeping medications. Indeed, sleep drugs are rarely used before and during the treatment. The global sleep quality was classified as poor in 88.9 % of cases at T0 and decreased to 5.7 % at T3. A high risk of sleep apnea was revealed by the STOP-BANG in 68.9 % of cases at T0 and 2.8 % of patient at T3 (p < 0.001).

CONCLUSIONS

Dupilumab improves the sleep quality and reduce the risk of sleep apnea in patients with severe CRSwNP. Its favorable effect occurs within 3 months and is maintained during the treatment.

Astrocyte regulation of extracellular space parameters across the sleep-wake cycle

Multiple subfields of neuroscience research are beginning to incorporate astrocytes into current frameworks of understanding overall brain physiology, neuronal circuitry, and disease etiology that underlie sleep and sleep-related disorders. Astrocytes have emerged as a dynamic regulator of neuronal activity through control of extracellular space (ECS) volume and composition, both of which can vary dramatically during different levels of sleep and arousal. Astrocytes are also an attractive target of sleep research due to their prominent role in the glymphatic system, a method by which toxic metabolites generated during wakefulness are cleared away. In this review we assess the literature surrounding glial influences on fluctuations in ECS volume and composition across the sleep-wake cycle. We also examine mechanisms of astrocyte volume regulation in glymphatic solute clearance and their role in sleep and wake states. Overall, findings highlight the importance of astrocytes in sleep and sleep research.

The potential for traditional Chinese therapy in treating sleep disorders caused by COVID-19 through the cholinergic anti-inflammatory pathway

Since the outbreak of Coronavirus disease (COVID-19) in 2019, it has spread rapidly across the globe. Sleep disorders caused by COVID-19 have become a major concern for COVID-19 patients and recovered patients. So far, there’s no effective therapy on this. Traditional Chinese therapy (TCT) has a great effect on sleep disorders, with rare side effects and no obvious withdrawal symptoms. The cholinergic anti-inflammatory pathway, a neuroregulatory pathway in the central nervous system that uses cholinergic neurons and neurotransmitters to suppress inflammatory responses, has been reported to be associated with sleep disorders and psychiatric symptoms. Many studies have shown that TCT activates the cholinergic anti-inflammatory pathway (CAP), inhibits inflammation, and relieves associated symptoms. Therefore, we believe that TCT may be a potential therapeutic strategy to alleviate sleep disorders induced by COVID-19 through CAP. In this review, we analyzed the relationship between cytokine storm induced by Coronavirus and sleep disorders, explained the influence of CAP on sleep disorders, discussed the TCT’s effect on CAP, and summarized the treatment effect of TCT on sleep disorders. Based on these practical researches and theoretical basis, we propose potential strategies to effectively improve the sleep disorders caused by COVID-19.

Sleep Disturbance and Alzheimer's Disease: The Glial Connection

Poor quality and quantity of sleep are very common in elderly people throughout the world. Growing evidence has suggested that sleep disturbances could accelerate the process of neurodegeneration. Recent reports have shown a positive correlation between sleep deprivation and amyloid-β (Aβ)/tau aggregation in the brain of Alzheimer's patients. Glial cells have long been implicated in the progression of Alzheimer's disease (AD) and recent findings have also suggested their role in regulating sleep homeostasis. However, how glial cells control the sleep-wake balance and exactly how disturbed sleep may act as a trigger for Alzheimer's or other neurological disorders have recently gotten attention. In an attempt to connect the dots, the present review has highlighted the role of glia-derived sleep regulatory molecules in AD pathogenesis. Role of glia in sleep disturbance and Alzheimer's progression.

Poor Sleep Quality is Linked to Elevated Extracellular Vesicle-Associated Inflammatory Cytokines in Warfighters With Chronic Mild Traumatic Brain Injuries

Background: Elevations of inflammatory cytokine levels occur immediately after mild traumatic brain injury (mTBI) and can persist for years. These elevations have been associated with neuropsychological outcomes, including depression and PTSD symptoms. Sleep disorders, another common sequelae of mTBI, are independently associated with inflammation in otherwise healthy individuals. However, whether sleep and inflammation are linked in chronic mTBI has not been reported.

Methods: A retrospective cross-sectional cohort of warfighters was used to investigate the hypothesis that inflammation may be linked to sleep quality in chronic mTBI. Clinical history, peripheral blood samples, and sleep quality scores were collected from 182 warfighters (n = 138 mTBI; n = 44 controls) during enrollment in the Chronic Effects of Neurotrauma Consortium study. Biomarkers of inflammation (IL-6, IL-10, TNFα cytokines) from plasma and plasma-derived extracellular vesicles (EVs) were quantified using single molecule array. Relationships between sleep quality and cytokine levels were assessed, controlling for age, sex, and BMI. Using clinical cutoff scores for sleep quality, mTBI patients were then divided into “good” and “poor” sleepers and cytokine levels compared between groups.

Results: In mTBI participants, sleep quality was significantly associated with EV levels of IL-10 [ß (SE) = 0.11 (0.04), p = 0.01] and TNFα [ß (SE) = 0.07 (0.03), p < 0.01]. When divided according to “good” versus “poor” sleepers, those reporting poor sleep had significantly elevated EV IL-10 compared to those reporting good sleep [ß (SE) = 0.12 (0.04), p < 0.01]. Plasma-derived associations were not significant. No associations were found between sleep quality and cytokine levels in controls.

Conclusion: These results suggest a significant relationship between sleep quality and chronic inflammation in mTBI patients. Clinically, mTBI patients with a high likelihood of sleep disorders demonstrate elevated levels of inflammatory cytokines. Signal from EVs, though smaller in magnitude, may have stronger clinical associations than from plasma. Sleep-focused interventions may also serve to regulate chronic inflammatory processes in these patients. Larger prospective studies are needed to investigate the mechanisms and therapeutic implications of the likely bi-directional relationship between sleep and inflammation following mTBI.

Sleep Disruption Worsens Seizures: Neuroinflammation as a Potential Mechanistic Link

Sleep disturbances, such as insomnia, obstructive sleep apnea, and daytime sleepiness, are common in people diagnosed with epilepsy. These disturbances can be attributed to nocturnal seizures, psychosocial factors, and/or the use of anti-epileptic drugs with sleep-modifying side effects. Epilepsy patients with poor sleep quality have intensified seizure frequency and disease progression compared to their well-rested counterparts. A better understanding of the complex relationship between sleep and epilepsy is needed, since approximately 20% of seizures and more than 90% of sudden unexpected deaths in epilepsy occur during sleep. Emerging studies suggest that neuroinflammation, (e.g., the CNS immune response characterized by the change in expression of inflammatory mediators and glial activation) may be a potential link between sleep deprivation and seizures. Here, we review the mechanisms by which sleep deprivation induces neuroinflammation and propose that neuroinflammation synergizes with seizure activity to worsen neurodegeneration in the epileptic brain. Additionally, we highlight the relevance of sleep interventions, often overlooked by physicians, to manage seizures, prevent epilepsy-related mortality, and improve quality of life.

Changed signals of blood adenosine and cytokines are associated with parameters of sleep and/or cognition in the patients with chronic insomnia disorder

OBJECTIVES

This study aimed to investigate whether plasma levels of adenosine, adenosine deaminase (ADA), and certain cytokines change in patients with chronic insomnia disorder (CID), and if so, whether these alterations are associated with poor sleep quality and cognitive dysfunction.

METHODS

Fifty-five CID patients were selected for the study, along with fifty-five healthy controls (HC) matched to the patients according to their basic data. All subjects completed sleep, emotion, and cognition assessments, with some CID patients also completing an overnight polysomnography. The plasma level of adenosine was measured using liquid chromatography-tandem mass spectrometry, while ADA level was quantified using a quantitative sandwich enzyme-linked immunosorbent assay. Levels of cytokines, including IL-1β, IL-2, IL-4, IL-6, IL-10, IL-12, TNF-α, and IFN-γ, were measured using Luminex liquid chip technology.

RESULTS

CID patients had a lower adenosine level, and higher levels of ADA and some of the cytokines (IL-1β, IL-2, IL-6, IL-10 and TNF-α) compared with controls. In the CID group, plasma concentrations of adenosine were negatively correlated with Pittsburgh Sleep Quality Index scores, while concentrations of IL-1β, IL-6 and TNF-α were positively correlated with these scores. Concentrations of IL-1β and TNF-α were negatively correlated with scores on the Chinese-Beijing Version of the Montreal Cognitive Assessment. Moreover, levels of IL-1β, TNF-α, IL-6, and IL-2 were positively correlated with memory test errors by CID patients after controlling for confounding factors.

CONCLUSIONS

The reduced adenosine and elevated cytokine levels of CID patients were associated with the severity of insomnia and/or cognitive dysfunction.

Are Anti-Inflammatory Cytokines Associated with Cognitive Impairment in Patients with Insomnia Comorbid with Depression? A Pilot Study

BACKGROUND

To distinguish insomnia comorbid with depression (ICD) from chronic insomnia disorder (CID) by exploring the relationship between serum levels of frequently overlooked anti-inflammatory cytokines and cognitive function.

METHODS

A total of 42 ICD patients, 63 CID patients, and 42 healthy control subjects were enrolled in the study. The Pittsburgh Sleep Quality Index and Hamilton Depression Rating Scale were used to assess sleep quality and depression severity, respectively. The Chinese-Beijing version of Montreal Cognitive Assessment scale (MoCA-C) and Nine-Box Maze Test (NBMT) were used to assess cognitive function. Serum levels of anti-inflammatory interleukins (IL-1RA, IL-4, IL-5, IL-10, IL-13, and IL-28A), transforming growth factor (TGF)-β1, granulocyte-macrophage colony-stimulating factor, interferon-γ, and the chemokine regulated upon activation, normal T cell expressed and secreted (RANTES) were measured by enzyme-linked immunosorbent assay.

RESULTS

The ICD group had significantly more errors in the spatial reference task (H=2.55, P_s=0.03) and spatial working memory task (H=5.67, P_s<0.01) of the NBMT, as well as lower levels of IL-1RA (H=-2.85, P_s=0.01), IL-4 (H=-3.28, P_s<0.01), IL-5 (H=-3.35, P_s<0.01), IL-10 (H=-4.46, P_s<0.01), and IL-28A (H=-2.75, P_s=0.02) than control subjects. Compared with the CID group, the ICD group had significantly more errors in the spatial reference memory task (H=-2.84, P_s=0.01) of the NBMT, and lower levels of IL-5 (H=3.41, P_s<0.01), IL-10 (H=5.30, P_s<0.01), IL-13 (H=3.89, P_s<0.01), and GM-CSF (H=2.72, P_s=0.02). A partial correlation analysis showed that the level of one or more of IL-4, IL-5, IL-10, IL-13, and TGF-β1 was positively correlated with cognitive function (MoCA-C score and/or performance in spatial memory task) in ICD patients.

CONCLUSION

ICD is a distinct condition that can be distinguished from CID based on immune dysfunction and specific types of cognitive dysfunction.

Microglia dynamics in sleep/wake states and in response to sleep loss

Sleep has an essential role for optimal brain function, but the cellular substrates for sleep regulation are not fully understood. Microglia, the immune cells of the brain, have gained increasingly more attention over the last two decades for their important roles in various brain functions that extend beyond their well-known immune function, including brain development, neuronal protection, and synaptic plasticity. Here we review recent advances in understanding: i) morphological and phenotypic dynamics of microglia including process motility/growth and gene/protein expression, and ii) microglia-neuron interactions including phagocytosis and contact at synapses which alters neuronal circuit activity, both under physiological state in the adult brain. We discuss how the microglia-neuron interactions particularly at synapses could influence microglia and neuronal activities across circadian cycles and sleep/wake states. We also review recent findings on how microglia respond to sleep loss. We conclude by pointing out key questions and proposing suggestions for future research to better understand the role of microglia in sleep regulation, sleep homeostasis, and the function of sleep.

The Sleep-Immune Crosstalk in Health and Disease

Sleep and immunity are bidirectionally linked. Immune system activation alters sleep, and sleep in turn affects the innate and adaptive arm of our body's defense system. Stimulation of the immune system by microbial challenges triggers an inflammatory response, which, depending on its magnitude and time course, can induce an increase in sleep duration and intensity, but also a disruption of sleep. Enhancement of sleep during an infection is assumed to feedback to the immune system to promote host defense. Indeed, sleep affects various immune parameters, is associated with a reduced infection risk, and can improve infection outcome and vaccination responses. The induction of a hormonal constellation that supports immune functions is one likely mechanism underlying the immune-supporting effects of sleep. In the absence of an infectious challenge, sleep appears to promote inflammatory homeostasis through effects on several inflammatory mediators, such as cytokines. This notion is supported by findings that prolonged sleep deficiency (e.g., short sleep duration, sleep disturbance) can lead to chronic, systemic low-grade inflammation and is associated with various diseases that have an inflammatory component, like diabetes, atherosclerosis, and neurodegeneration. Here, we review available data on this regulatory sleep-immune crosstalk, point out methodological challenges, and suggest questions open for future research.

Molecular Mechanisms of Cancer-Induced Sleep Disruption

Sleep is essential for health. Indeed, poor sleep is consistently linked to the development of systemic disease, including depression, metabolic syndrome, and cognitive impairments. Further evidence has accumulated suggesting the role of sleep in cancer initiation and progression (primarily breast cancer). Indeed, patients with cancer and cancer survivors frequently experience poor sleep, manifesting as insomnia, circadian misalignment, hypersomnia, somnolence syndrome, hot flushes, and nightmares. These problems are associated with a reduction in the patients' quality of life and increased mortality. Due to the heterogeneity among cancers, treatment regimens, patient populations and lifestyle factors, the etiology of cancer-induced sleep disruption is largely unknown. Here, we discuss recent advances in understanding the pathways linking cancer and the brain and how this leads to altered sleep patterns. We describe a conceptual framework where tumors disrupt normal homeostatic processes, resulting in aberrant changes in physiology and behavior that are detrimental to health. Finally, we discuss how this knowledge can be leveraged to develop novel therapeutic approaches for cancer-associated sleep disruption, with special emphasis on host-tumor interactions.

Possible Molecular Mediators Involved and Mechanistic Insight into Fibromyalgia and Associated Co-morbidities

Fibromyalgia is a chronic complex syndrome of non-articulate origin characterized by musculoskeletal pain, painful tender points, sleep problems and co-morbidities including depression, migraine. The etiopathogenesis of fibromyalgia is complex, variable and remains inconclusive. The etiological factors that have been defined include stress, genetic predisposition and environmental components. As per the reports of the American College of Rheumatology (ACR) the prevalence of fibromyalgia varies from 2 to 22% among the general population with poor diagnostic features primarily pain. Fibromyalgia encompasses a spectrum of co-morbid conditions with multifarious pathogenesis. The highly prevalent manifestations of fibromyalgia include heterogeneous pain and aches. Biochemical and neurobiological elements of fibromyalgia include neurotransmitters, hypothalamic pituitary adrenal axis (HPA axis), inflammatory cytokines, monoaminergic pathway, opioid peptides, sex hormones, nerve growth factor (NGF) and local free radical insult. An imbalance in the serotonergic system is the major underlying etiological factor that has been explored most widely. Owing to complex interplay of diverse pathophysiological pathways, overlapping co-morbidities such as depression have been clinically observed. Therapeutic management of fibromyalgia involves both non pharmacological and pharmacological measures. The current review presents various dysregulations and their association with symptoms of fibromyalgia along with their underlying neurobiological aspects.

Mental Health in Allergic Rhinitis: Depression and Suicidal Behavior

A high proportion of suicides visit their medical provider in the month prior to death, but depression, suicidal thoughts, and substance use are seldom addressed. For the clinicians routinely treating a substantial patient population with allergic diseases, there are additional concerns, as allergy has been linked with both depression and suicidal behavior. While psychotropic medications may affect diagnosis of allergies, medications used to treat allergies impact mood and behavior. Thus, we present an overview of the overlap of allergic rhinitis with depression and suicidal behavior in adults, based on clinical and epidemiological data, and our research and clinical experience. In summary, we suggest: 1) inquiring among patients with allergies about personal and family history of depression, substance use disorders, suicidal ideation and attempts 2) increased mindfulness regarding the potential effects of allergy medications on mood and behavior; and 3) for people identified with certain types of depression or increased suicide risk, a systematic multilevel collaborative approach. While for practical reasons the majority of patients with depression will continue to be treated by general or family practitioners, the allergy-treating provider should always consider integrated care for bipolar, psychotic or suicidal depression and incomplete remission, or relapsing and highly recurrent course. While awaiting results of much needed basic and clinical research to guide clinical approach for patients with comorbid allergic rhinitis and depression, the simple steps recommended here are expected to improved clinical outcomes in depression, including, on a large scale, reduced premature deaths by suicide.

Sleep dysfunction and its association to chronic rhinosinusitis: Updated review

Background

Poor sleep has significant effects on health contributing to increased morbidity and mortality. The direct and indirect costs of sleep dysfunction total well in to the billions of dollars annually in the United States. Chronic rhinosinusitis (CRS) affects up to 16% of the US population and has been linked to poor sleep quality with up to three quarters of patients with CRS reporting poor sleep quality. There is a growing body of literature evaluating the relationship between sleep and CRS. In this review, we organize and present the current knowledge on the associations between sleep and CRS as well as identify areas for further investigation.

Data sources

A structured literature search from 1946 to 2016 was conducted in the English language using OVID MEDLINE database, PubMed, and EMBASE.

Review methods

Abstracts were reviewed for relevance and appropriate studies were included in the narrative review.

Results

Studies were analyzed and discussed as they pertained to the following categories of CRS and sleep: (1) subjective measures of sleep dysfunction, (2) objective measures of sleep dysfunction, and (3) outcomes on sleep quality following treatment of CRS. Articles on the pathophysiology of sleep dysfunction in CRS were separately reviewed.

Conclusions

An evolving body of research demonstrates that quality of sleep is compromised in the majority of patients with CRS. Following treatment of CRS, there is significant improvement in subjective sleep quality, but additional research investigating objective measures following treatment is still needed. Additionally, further investigation is required to better elucidate the underlying pathophysiology of the relationship between sleep dysfunction and CRS.

Level of Evidence

N/A.

Impact of Serum Cytokine Levels on EEG-Measured Arousal Regulation in Patients with Major Depressive Disorder and Healthy Controls

BACKGROUND

In major depressive disorder (MDD), findings include hyperstable regulation of brain arousal measured by electroencephalography (EEG) vigilance analysis and alterations in serum levels of cytokines. It is also known that cytokines affect sleep-wake regulation. This study investigated the relationship between cytokines and EEG vigilance in participants with MDD and nondepressed controls, and the influence of cytokines on differences in vigilance between the two groups.

METHODS

In 60 patients with MDD and 129 controls, 15-min resting-state EEG recordings were performed and vigilance was automatically assessed with the VIGALL 2.0 (Vigilance Algorithm Leipzig). Serum levels of the wakefulness-promoting cytokines interleukin (IL)-4, IL-10, IL-13 and somnogenic cytokines tumor necrosis factor-α, interferon-x03B3; and IL-2 were measured prior to the EEG.

RESULTS

Summed wakefulness-promoting cytokines, but not somnogenic cytokines, were significantly associated with the time course of EEG vigilance in the MDD group only. In both groups, IL-13 was significantly associated with the course of EEG vigilance. In MDD compared to controls, a hyperstable EEG vigilance regulation was found, significant for group and group × time course interaction. After controlling for wakefulness-promoting cytokines, differences in vigilance regulation between groups remained significant.

CONCLUSIONS

The present study demonstrated a relationship between wakefulness-promoting cytokines and objectively measured EEG vigilance as an indicator for brain arousal. Altered brain arousal regulation in MDD gives support for future evaluation of vigilance measures as a biomarker in MDD. Since interactions between cytokines and EEG vigilance only moderately differed between the groups and cytokine levels could not explain the group differences in EEG vigilance regulation, cytokines and brain arousal regulation are likely to be associated with MDD in independent ways.

Role of interleukin-10 (IL-10) in regulation of GABAergic transmission and acute response to ethanol

Mounting evidence indicates that ethanol (EtOH) exposure activates neuroimmune signaling. Alterations in pro-inflammatory cytokines after acute and chronic EtOH exposure have been heavily investigated. In contrast, little is known about the regulation of neurotransmission and/or modulation by anti-inflammatory cytokines in the brain after an acute EtOH exposure. Recent evidence suggests that interleukin-10 (IL-10), an anti-inflammatory cytokine, is upregulated during withdrawal from chronic EtOH exposure. In the present study, we show that IL-10 is increased early (1 h) after a single intoxicating dose of EtOH (5 g/kg, intragastric) in Sprague Dawley rats. We also show that IL-10 rapidly regulates GABAergic transmission in dentate gyrus neurons. In brain slice recordings, IL-10 application dose-dependently decreases miniature inhibitory postsynaptic current (mIPSC) area and frequency, and decreases the magnitude of the picrotoxin sensitive tonic current (Itonic), indicating both pre- and postsynaptic mechanisms. A PI3K inhibitor LY294002 (but not the negative control LY303511) ablated the inhibitory effects of IL-10 on mIPSC area and Itonic, but not on mIPSC frequency, indicating the involvement of PI3K in postsynaptic effects of IL-10 on GABAergic transmission. Lastly, we also identify a novel neurobehavioral regulation of EtOH sensitivity by IL-10, whereby IL-10 attenuates acute EtOH-induced hypnosis. These results suggest that EtOH causes an early release of IL-10 in the brain, which may contribute to neuronal hyperexcitability as well as disturbed sleep seen after binge exposure to EtOH. These results also identify IL-10 signaling as a potential therapeutic target in alcohol-use disorders and other CNS disorders where GABAergic transmission is altered.

Functions and Mechanisms of Sleep

Sleep is a complex physiological process that is regulated globally, regionally, and locally by both cellular and molecular mechanisms. It occurs to some extent in all animals, although sleep expression in lower animals may be co-extensive with rest. Sleep regulation plays an intrinsic part in many behavioral and physiological functions. Currently, all researchers agree there is no single physiological role sleep serves. Nevertheless, it is quite evident that sleep is essential for many vital functions including development, energy conservation, brain waste clearance, modulation of immune responses, cognition, performance, vigilance, disease, and psychological state. This review details the physiological processes involved in sleep regulation and the possible functions that sleep may serve. This description of the brain circuitry, cell types, and molecules involved in sleep regulation is intended to further the reader's understanding of the functions of sleep.

Association of innate immune single-nucleotide polymorphisms with the electroencephalogram during desflurane general anaesthesia

The electroencephalogram (EEG) records the electrical activity of the brain and enables effects of anaesthetic drugs on brain functioning to be monitored. Identification of genes contributing to EEG variability during anaesthesia is important to the clinical application of anaesthesia monitoring and may provide an avenue to identify molecular mechanisms underlying the generation and regulation of brain oscillations. Central immune signalling can impact neuronal activity in the brain and accumulating evidence suggests an important role for cytokines as neuronal modulators. We tested 21 single-nucleotide polymorphisms (SNPs) in immune-related genes for associations with three anaesthesia-induced EEG patterns; spindle amplitude, delta power and alpha power, during general anaesthesia with desflurane in 111 patients undergoing general, gynaecological or orthopaedic surgery. Wide inter-patient variability was observed for all EEG variables. MYD88 rs6853 (p = 6.7 × 10(-4)) and IL-1β rs1143627 in conjunction with rs6853 (p = 1.5 × 10(-3)) were associated with spindle amplitude, and IL-10 rs1800896 was associated with delta power (p = 1.3 × 10(-2)) suggesting involvement of cytokine signalling in modulation of EEG patterns during desflurane anaesthesia. BDNF rs6265 was associated with alpha power (p = 3.9 × 10(-3)), suggesting differences in neuronal plasticity might also influence EEG patterns during desflurane anaesthesia. This is the first study we are aware of that has investigated genetic polymorphisms that may influence the EEG during general anaesthesia.

Antisomnogenic cytokines, quality of life, and chronic rhinosinusitis: a pilot study

OBJECTIVES/HYPOTHESIS

Sleep disturbance, reduced quality of life (QOL), and other components of "sickness behavior" in patients with chronic rhinosinusitis (CRS) are poorly understood. These complex changes in central behavior are due to the effects of immune mediators acting in the brain. We hypothesized that immune mediators that have been associated with CRS are also associated with sickness behavior, somnifacient complaints, and CRS disease-specific QOL.

STUDY DESIGN

Pilot study.

METHODS

Twenty patients with CRS were prospectively enrolled and completed the Pittsburgh Sleep Quality Index (PSQI), disease-specific QOL, and olfactory instruments. Ethmoid mucosa was obtained and reverse transcription-polymerase chain reaction was performed for the cytokines interleukin (IL)-4, -13, and transforming growth factor-β (TGF-β). Average change in crossover threshold was calculated, and differences in gene expression were correlated with sleep quality, CRS-specific QOL, and disease severity.

RESULTS

Patients with CRS reported overall poor sleep quality and poor CRS-specific QOL with significant correlations between them. Increased expression of TGF-β (r = -0.443; P = .050) and IL-4 (r = -0.548; P = .012) correlated with sleep dysfunction, whereas IL-13 expression was linearly associated with worse sleep quality (PSQI scores r = -0.417; P = .075). IL-4 and TGF-β expression was not associated with CRS disease severity or QOL, whereas significantly higher levels of IL-13 expression correlated with worse CRS disease severity and QOL.

CONCLUSIONS

Patients with CRS exhibited behavioral changes commonly referred to as sickness behavior, which include poor sleep quality and reduced QOL. The upregulation of IL-4 and TGF-β may contribute to inflammatory brain-mediated effects on sleep quality, whereas IL-13 may be a pleiotropic signaling molecule influencing sleep, QOL, and CRS disease severity.

LEVEL OF EVIDENCE

2b.

Chronic rhinosinusitis and sleep: a contemporary review

BACKGROUND

Patients with chronic rhinosinusitis (CRS) exhibit centrally mediated behavioral changes commonly referred to as "sickness behavior." Sleep alteration is a component of sickness behavior which is estimated to affect up to 70 million patients annually. Patients with CRS have poor sleep quality, and little is known about the underlying etiology and pathophysiology. This narrative review aims to further organize and present the current knowledge associating sleep and CRS.

METHODS

A literature search was conducted of the OVID MEDLINE database using key search words including: "chronic rhinosinusitis," "sleep," "sleep disorders," and "sleep dysfunction." Additional keywords "nasal obstruction," "nasal polyp," and "fatigue" were identified and used to further delineate relevant articles.

RESULTS

The articles that specifically addressed sleep and CRS were dissected and presented as follows: (1) chronic rhinosinusitis and sleep; (2) chronic rhinosinusitis and fatigue; (3) chronic rhinosinusitis, nasal obstruction, and sleep; and (4) pathophysiology of sleep in chronic rhinosinusitis (cytokines in both sleep and chronic rhinosinusitis and their association to the neuroimmune biology of chronic rhinosinusitis).

CONCLUSION

Patients with CRS have sleep dysfunction that is associated with their disease severity and overall quality of life. The etiology of sleep dysfunction in CRS is most likely multifactorial. Increasing evidence suggests sleep dysfunction in patients with CRS is partly due to the inflammatory disease process, and sleep physiology in patients with CRS may be actively regulated by the inflammatory component of the disease.

Metabolomic analysis identifies inflammatory and noninflammatory metabolic effects of genetic modification in a mouse model of Crohn's disease

Interleukin-10 is an immunosuppressive cytokine involved in the regulation of gastrointestinal mucosal immunity toward intestinal microbiota. Interleukin-10-deficient (IL10(-/-)) mice develop Crohn's disease-like colitis unless raised in germ-free conditions. Previous gas chromatography-mass spectrometry (GC-MS) metabolomic analysis revealed urinary metabolite differences between IL10(-/-) and wildtype C57BL/6 mice. To determine which of these differences were specifically associated with intestinal inflammation arising from IL10-deficiency, urine samples from IL10(-/-) and wildtype mice, housed in either conventional or specific pathogen-free conditions, were subjected to GC-MS metabolomic analysis. Fifteen metabolite differences, including fucose, xanthurenic acid, and 5-aminovaleric acid, were associated with intestinal inflammation. Elevated urinary levels of xanthurenic acid in IL10(-/-) mice were attributed to increased production of kynurenine metabolites that may induce T-cell tolerance toward intestinal microbiota. Liquid chromatography-mass spectrometry analysis confirmed that plasma levels of kynurenine and 3-hydroxykynurenine were elevated in IL10(-/-) mice. Eleven metabolite differences, including glutaric acid, 2-hydroxyglutaric acid, and 2-hydroxyadipic acid, were unaffected by the severity of inflammation. These metabolite differences may be associated with residual genes from the embryonic stem cells of the 129P2 mouse strain that were used to create the IL10(-/-) mouse, or may indicate novel functions of IL10 unrelated to inflammation.

Cytokines across the night in chronic fatigue syndrome with and without fibromyalgia

The symptoms of chronic fatigue syndrome (CFS) are consistent with cytokine dysregulation. This has led to the hypothesis of immune dysregulation as the cause of this illness. To further test this hypothesis, we did repeated blood sampling for cytokines while patients and matched healthy controls slept in the sleep lab. Because no one method for assaying cytokines is acknowledged to be better than another, we assayed for protein in serum, message in peripheral blood lymphocytes (PBLs), and function in resting and stimulated PBLs. We found no evidence of proinflammatory cytokine upregulation. Instead, in line with some of our earlier studies, we did find some evidence to support a role for an increase in interleukin-10, an anti-inflammatory cytokine. Although the changes were small, they may contribute to the common complaint in CFS patients of disrupted sleep.

Optogenetic deconstruction of sleep-wake circuitry in the brain

How does the brain regulate the sleep–wake cycle? What are the temporal codes of sleep and wake-promoting neural circuits? How do these circuits interact with each other across the light/dark cycle? Over the past few decades, many studies from a variety of disciplines have made substantial progress in answering these fundamental questions. For example, neurobiologists have identified multiple, redundant wake-promoting circuits in the brainstem, hypothalamus, and basal forebrain. Sleep-promoting circuits have been found in the preoptic area and hypothalamus. One of the greatest challenges in recent years has been to selectively record and manipulate these sleep–wake centers in vivo with high spatial and temporal resolution. Recent developments in microbial opsin-based neuromodulation tools, collectively referred to as “optogenetics,” have provided a novel method to demonstrate causal links between neural activity and specific behaviors. Here, we propose to use optogenetics as a fundamental tool to probe the necessity, sufficiency, and connectivity of defined neural circuits in the regulation of sleep and wakefulness.

Interleukin-10: a key cytokine in depression?

An increasing body of evidence implicates proinflammatory cytokines in psychiatric disorders, namely, in depression. Of notice, recent studies showed that anti-inflammatory cytokines, such as IL-10, also modulate depressive-like behavior. In this article, we propose that the anti-inflammatory cytokine IL-10 is a putative link between two of the most widely reported phenomenon observed in depressed patients: the disruption of the hypothalamic-pituitary-adrenal axis and the imbalanced production of cytokines. If so, IL-10 might represent a novel target for antidepressant therapy.

Plasma cytokine fluctuations over time in healthy controls and patients with fibromyalgia

We examined the pattern of cytokine secretion across the 24-hr day for women with widespread pain and tenderness having the diagnosis of fibromyalgia (FM) and matched healthy controls. Subjects were given time to habituate to being in a clinical research laboratory environment and then were sampled for cytokines without their being disturbed for a 24-hr period including an 8-hr sleep period. Cytokine levels were uniformly low but characterized by bursts of secretion. Bursting occurred either in singlets or in doublets with a range from 88 to 131 mins between doublet bursts. There was an element of synchronization of these bursts with most occurring at the beginning of sampling. FM patients showed a shift to increased IL-10 in the nighttime compared to controls. The relation between this anti-inflammatory cytokine to the pro-inflammatory cytokines studied also differed between groups: FM patients showed an increased ratio of IL-10 burst amplitude to that of pro-inflammatory cytokines IL-1beta, IL-8, and TNF-alpha. We interpret this to indicate a skew away from the normal balance favoring pro-inflammatory cytokines in controls toward one favoring an anti-inflammatory response in FM. These changes toward anti-inflammatory predominance in FM may explain their common complaint of disturbed sleep because these cytokines are known to disrupt sleep.

Allergy: a risk factor for suicide?

The rates of depression, anxiety, and sleep disturbance (suicide risk factors) are greater in patients with allergic rhinitis than in the general population. The rate of allergy is also greater in patients with depression. Preliminary data suggest that patients with a history of allergy may have an increased rate of suicide. Clinicians should actively inquire to diagnose allergy in patients with depression and depression in patients with allergy. Spring peaks of suicide are highly replicated, but their origin is poorly understood. Preliminary epidemiologic data suggest that seasonal spring peaks in aeroallergens are associated with seasonal spring peaks in suicide. Our research in Brown Norway rats demonstrates that sensitization and exposure to aeroallergens induces anxiety-like and aggressive behaviors as well as allergy-related helper T-cell type 2 (Th2) cytokine gene expression in the prefrontal cortex. Thus, it is possible that sensitization and exposure to aeroallergens, which peak in spring, may be conducive to seasonal exacerbation of suicide risk factors such as anxiety, depression, hostility/aggression, and sleep disturbance. Connecting allergy with suicide and suicide risk factors adds to previous neurologic literature connecting allergy with migraines and seizure disorders. Our recent report of Th2 (allergy-mediating) cytokine expression in the orbitofrontal cortex of suicide victims should lead to future studies to test the hypothesis that mediators of allergic inflammation in the nasal cavities may result in Th2 cytokine expression in the brain, influencing affect and behavioral modulation. Certain medications used to treat allergy can exacerbate suicide risk factors, potentially worsening suicide risk and even triggering suicide. Systemic (but not topical) corticosteroids have been associated with manic and depressive episodes and mixed mood states. Recently, the US Food and Drug Administration started investigating the possibility that montelukast may trigger suicide. Although this association requires further exploration and confirmation, clinicians should err on the side of caution, inquiring about past suicide attempts; hopelessness; reasons for living; and suicidal ideation, intent, or plan; and referring the patient to a mental health professional for evaluation if appropriate.

Interleukin-8 promotes non-rapid eye movement sleep in rabbits and rats

Interleukin-8 (IL-8) is a cytokine found in the brain. In this study, the ability of IL-8 to induce sleep in rabbits and rats was investigated. Twenty-seven Sprague-Dawley rats and 16 male New Zealand White rabbits were provided electroencephalographic (EEG) electrodes, a brain thermistor, and a lateral intracerebroventricular cannula. The animals were injected intracerebroventricularly (i.c.v.) with pyrogen-free saline and, one of the following doses of IL-8 on a separate day: 1.25 or 12.5 ng in rabbits and 10, 50, or 100 ng in rats. EEG, brain temperature, and motor activity were recorded for 23 h after the i.c.v. injections. IL-8 increased time spent in non-rapid eye movement sleep (NREMS) without affecting rapid eye movement sleep (REMS). In rabbits, both doses of IL-8 promoted NREMS. In rats, the 10 and 50 ng doses of IL-8 failed to affect sleep, but the 100 ng dose of IL-8 enhanced NREMS. EEG slow-wave activity during NREMS was increased after the high dose of IL-8 in rabbits. IL-8 also induced fever in rabbits but not rats. Heat inactivated IL-8 did not alter any of the parameters measured. Current results support the notion that the brain cytokine network plays a role in sleep regulation.

Brain-immune interactions in sleep

This chapter discusses various levels of interactions between the brain and the immune system in sleep. Sleep-wake behavior and the architecture of sleep are influenced by microbial products and cytokines. On the other hand, sleep processes, and perhaps also specific sleep states, appear to promote the production and/or release of certain cytokines. The effects of immune factors such as endotoxin and cytokines on sleep reveal species specificity and usually strong dependence on parameters such as substance concentration, time relative to administration or infection with microbial products, and phase relation to sleep and/or the light-dark cycle. For instance, endotoxin increased SWS and EEG SWA in humans only at very low concentrations, whereas higher concentrations increased sleep stage 2 only, but not SWS. In animals, increases in NREM sleep and SWA were more consistent over a wide range of endotoxin doses. Also, administration of pro-inflammatory cytokines such as IL-6 and IFN-alpha in humans acutely disturbed sleep while in rats such cytokines enhanced SWS and sleep. Overall, the findings in humans indicate that strong nonspecific immune responses are acutely linked to an arousing effect. Although subjects feel subjectively tired, their sleep flattens. However, some observations indicate a delayed enhancing effect on sleep which could be related to the induction of secondary, perhaps T-cell-related factors. This would also fit with results in animals in which the T-cell-derived cytokine IL-2 enhanced sleep while cytokines with immunosuppressive functions like IL-4 and L-10 suppressed sleep. The most straightforward similarity in the cascade of events inducing sleep in both animals and humans is the enhancing effect of GHRH on SWS, and possibly the involvement of the pro-inflammatory cytokine systems of IL-1 beta and TNF-alpha. The precise mechanisms through which administered cytokines influence the central nervous system sleep processes are still unclear, although extensive research has identified the involvement of various molecular intermediates, neuropeptides, and neurotransmitters (cp. Fig. 5, Section III.B). Cytokines are not only released and found in peripheral blood mononuclear cells, but also in peripheral nerves and the brain (e.g., Hansen and Krueger, 1997; März et al., 1998). Cytokines are thereby able to influence the central nervous system sleep processes through different routes. In addition, neuronal and glial sources have been reported for various cytokines as well as for their soluble receptors (e.g., Kubota et al., 2001a). Links between the immune and endocrine systems represent a further important route through which cytokines influence sleep and, vice versa, sleep-associated processes, including variations in neurotransmitter and neuronal activity may influence cytokine levels. The ability of sleep to enhance the release and/or production of certain cytokines was also discussed. Most consistent results were found for IL-2, which may indicate a sleep-associated increase in activity of the specific immune system. Furthermore, in humans the primary response to antigens following viral challenge is enhanced by sleep. In animals results are less consistent and have focused on the secondary response. The sleep-associated modulation in cytokine levels may be mediated by endocrine parameters. Patterns of endocrine activity during sleep are probably essential for the enhancement of IL-2 and T-cell diurnal functions seen in humans: Whereas prolactin and GH release stimulate Th1-derived cytokines such as IL-2, cortisol which is decreased during the beginning of nocturnal sleep inhibits Th1-derived cytokines. The immunological function of neurotrophins, in particular NGF and BDNF, has received great interest. Effects of sleep and sleep deprivation on this cytokine family are particularly relevant in view of the effects these endogenous neurotrophins can have not only on specific immune functions and the development of immunological memories, but also on synaptic reorganization and neuronal memory formation.

Disordered sleep, nocturnal cytokines, and immunity in alcoholics

OBJECTIVE

Alcoholics who are at risk for infectious disease show profound disturbances of sleep along with decrements of cellular immunity. This study examined the relationships between sleep, nocturnal expression of immunoregulatory cytokines, and natural killer (NK) cell activity in alcoholic patients as compared with control subjects.

METHODS

Alcoholic patients (N = 24) and comparison control subjects (N = 23) underwent all-night polysomnography and serial blood sampling at 23:00, 03:00, and 06:30 hours. Stimulated expression of T(H)1 (interferon gamma, IFN-gamma), anti-inflammatory/T(H)2 (interleukin 10, IL-10), and proinflammatory cytokines (IL-6) was measured along with NK cell activity across the night.

RESULTS

Alcoholic patients showed lower levels of IL-6 production, suppression of the IL-6/IL-10 ratio, and a reduction of NK cell activity, coupled with losses of delta sleep and increases of rapid eye movement sleep, as compared with control subjects. In addition, alcoholics showed a persistent low ratio of IFN-gamma/IL-10 and reduced levels of NK cell activity, whereas controls had increases of these two immune measures across the night. IL-6 also differentially changed in the two groups; alcoholics showed increases and controls had decreases of IL-6 from 03:00 hours to 06:30 hours. At 06:30 hours, rapid eye movement sleep predicted increases of IL-6 and decreases of NK cell activity independent of the relative contribution of age and chronic alcohol consumption. At 23:00 hours before sleep onset, levels of IL-10 predicted subsequent amounts of delta sleep.

CONCLUSIONS

These data further implicate sleep in the regulation of immune function and suggest that disordered sleep contributes to immune alterations in patients with chronic alcoholism. Moreover, the association between awake levels of the anti-inflammatory/T(H)2 cytokine IL-10 and subsequent amounts of delta sleep support the notion of a bidirectional interplay between cytokines and sleep in humans.

Cytokines and cognition--the case for a head-to-toe inflammatory paradigm

The brain is not only immunologically active of its own accord, but also has complex peripheral immune interactions. Given the central role of cytokines in neuroimmmunoendocrine processes, it is hypothesized that these molecules influence cognition via diverse mechanisms. Peripheral cytokines penetrate the blood-brain barrier directly via active transport mechanisms or indirectly via vagal nerve stimulation. Peripheral administration of certain cytokines as biological response modifiers produces adverse cognitive effects in animals and humans. There is abundant evidence that inflammatory mechanisms within the central nervous system (CNS) contribute to cognitive impairment via cytokine-mediated interactions between neurons and glial cells. Cytokines mediate cellular mechanisms subserving cognition (e.g., cholinergic and dopaminergic pathways) and can modulate neuronal and glial cell function to facilitate neuronal regeneration or neurodegeneration. As such, there is a growing appreciation of the role of cytokine-mediated inflammatory processes in neurodegenerative diseases such as Alzheimer's disease and vascular dementia. Consistent with their involvement as mediators of bidirectional communication between the CNS and the peripheral immune system, cytokines play a key role in the hypothalamic-pituitary-adrenal axis activation seen in stress and depression. In addition, complex cognitive systems such as those that underlie religious beliefs, can modulate the effects of stress on the immune system. Indirect means by which peripheral or central cytokine dysregulation could affect cognition include impaired sleep regulation, micronutrient deficiency induced by appetite suppression, and an array of endocrine interactions. Given the multiple levels at which cytokines are capable of influencing cognition it is plausible that peripheral cytokine dysregulation with advancing age interacts with cognitive aging.

In vitro cytokine secretion in individuals with schizophrenia: results, confounding factors, and implications for further research

The present paper reviews the results of all publications on in vitro cytokine secretion in patients with schizophrenia, as published by March 2001. The authors supply easy to read tables with respect to the individual cytokines and soluble cytokine receptors investigated, the in vitro methodology used, characterization of the patient samples, and the results on cytokine secretion as stated in these studies. Inconsistent results, e.g., regarding in vitro secretion of IL-2 with 11/18 studies finding decreased secretion, 5/18 finding no change, and 2/18 finding increases, cannot systematically be correlated with any methodological procedures nor any diagnostic subtypes, per se. However, factors such as medication and cigarette smoking are likely to play a role. The authors suggest that more hypothesis-driven research, together with more carefully designed studies, as well as better communication between basic or animal researchers and clinicians might help to answer the question of whether there are meaningful peripheral changes in the immune system related to schizophrenia.

Interleukin-18 promotes sleep in rabbits and rats

Interleukin (IL)-1beta is involved in physiological sleep regulation. IL-18 is a member of the IL-1 family, and its signal-transduction mechanism is similar to that of IL-1. Therefore, we hypothesized that IL-18 might also be involved in sleep regulation. Three doses of IL-18 (10, 100, and 500 ng) were injected intracerebroventricularly (icv) into rabbits at the onset of the dark period. The two higher doses of IL-18 markedly increased non-rapid eye movement sleep (NREMS), accompanied by increases in brain temperature (Tbr). These effects were lost after the heat inactivation of IL-18. The 500 ng of IL-18 injection during the light period also increased NREMS and Tbr. Similar results were obtained after icv injection of 100 ng of IL-18 into rats. Furthermore, intraperitoneal injection of 30 microg/kg of IL-18 slightly, but significantly, increased NREMS, whereas it significantly decreased electroencephalogram slow-wave activity in rats. Intraperitoneal IL-18 failed to induce fever. An anti-human IL-18 antibody had little effect on spontaneous sleep in rabbits, although the anti-IL-18 antibody significantly attenuated muramyl dipeptide-induced sleep. These data suggest that IL-18 is involved in mechanisms of sleep responses to infection.

Cytokine- and microbially induced sleep responses of interleukin-10 deficient mice

Interleukin (IL)-1 and tumor necrosis factor (TNF) promote slow-wave sleep (SWS), whereas IL-10 inhibits the synthesis of IL-1 and TNF and promotes waking. We evaluated the impact of endogenous IL-10 on sleep-wake behavior by studying mice that lack a functional IL-10 gene. Under baseline conditions, C57BL/6-IL-10 knockout (KO) mice spent more time in SWS during the dark phase of the light-dark cycle than did genetically intact C57BL/6 mice. The two strains of mice showed generally comparable responses to treatment with IL-1, IL-10, or influenza virus, but differed in their responses to lipopolysaccharide (LPS). In IL-10 KO mice, LPS induced an initial transient increase and a subsequent prolonged decrease in SWS, as well as profound hypothermia. These responses were not observed in LPS-treated C57BL/6 mice. These data demonstrate that in the absence of endogenous IL-10, spontaneous SWS is increased and the impact of LPS on vigilance states is altered. Collectively, these observations support a role for IL-10 in sleep regulation and provide further evidence for the involvement of cytokines in the regulation of sleep.

Sleep deprivation but not a whisker trim increases nerve growth factor within barrel cortical neurons

Sleep is hypothesized to influence activity-driven changes in the brain microcircuitry. A change in the barrel cortex following the removal of the mystacial whiskers in rats is a model for synaptic plasticity. This model was combined with sleep deprivation and immunoreactivity for nerve growth factor (NGF) was determined. Sleep deprivation for 6 h after light onset significantly increased the number of NGF-immunoreactive pyramidal neurons in layer V of the barrel cortex. However, unilateral trimming of mystacial whiskers did not affect NGF immunoreactivity in the contralateral or ipsilateral barrel cortices when rats were allowed to sleep. If the rats received a unilateral whisker cut at light onset, and subsequently were deprived of sleep, increases in the NGF-immunoreactive neurons were only observed in the barrel cortex on the side that received input from the remaining intact whiskers. In contrast, NGF immunoreactivity on the side contralateral to the cut whiskers decreased in sleep-deprived animals to levels below those observed in the control animals that were allowed to sleep. These results suggest that NGF expression is influenced by the interaction of sleep, afferent input and the nature of ongoing synaptic reorganization. Further, results are consistent with the hypothesis that growth factors, such as NGF, form part of the mechanism responsible for sleep regulation and that they also form one facet of sleep-related synaptic plasticity.

Glial cell line-derived neurotrophic factor promotes sleep in rats and rabbits

Various growth factors (e.g., growth hormone-releasing hormone, acidic fibroblast growth factor, nerve growth factor, brain-derived neurotrophic factor, and interleukin-1) are implicated in sleep regulation. It is hypothesized that neuronal activity enhances the production of such growth factors, and they in turn form part of the sleep regulatory mechanism. Glial cell line-derived neurotrophic factor (GDNF) promotes development, differentiation, maintenance, and regeneration of neurons, and its production is induced by well-characterized sleep regulatory substances such as interleukin-1 and tumor necrosis factor. Therefore, we investigated whether GDNF would promote sleep. Twenty-six male Sprague-Dawley rats and 30 male New Zealand White rabbits were surgically implanted with electroencephalogram (EEG) and electromyogram (EMG; rats only) electrodes, a brain thermistor, and a lateral intracerebroventricular cannula. The animals were injected intracerebroventricularly with pyrogen-free saline and on a separate day with one of the following doses of GDNF: 5, 50, and 500 ng in rabbits and 50 and 500 ng in rats. The EEG, brain temperature, EMG (in rats), and motor activity (in rabbits) were recorded for 23 h after the intracerebroventricular injection. GDNF (500-ng dose) increased the time spent in nonrapid eye movement sleep in both rats and rabbits. Rapid eye movement sleep was not affected by the lower doses of GDNF but was inhibited in rabbits after the high dose. EEG slow-wave activity was not affected by GDNF. The current results provide further evidence that various growth factors are involved in sleep regulation.

Anti-inflammatory cytokines: expression and action in the brain

Transforming growth factor-beta(1) (TGF-beta(1)) and interleukin (IL)-10 gene expression is equivocal in normal brain and upregulated in over a dozen central and peripheral diseases/disorders. The patterns of specific expression of cytokines differ in these diseases. Published data indicate that these cytokines are produced by and act on both neurons and glial cells. Although their actions are commonly viewed as 'anti-inflammatory', they protect neurons and downregulate the responses of glial cells to diseases/disorders in the absence of inflammation. Their actions counterbalance the actions of elevated IL-1 and/or tumor necrosis factor-alpha to maintain homeostasis. Their therapeutic potential will be realized by improving our understanding of their place in neural cytokine networks.

Interleukin-13 and transforming growth factor-beta1 inhibit spontaneous sleep in rabbits

Proinflammatory cytokines, including interleukin-1beta and tumor necrosis factor-alpha are involved in physiological sleep regulation. Interleukin (IL)-13 and transforming growth factor (TGF)-beta1 are anti-inflammatory cytokines that inhibit proinflammatory cytokines by several mechanisms. Therefore, we hypothesized that IL-13 and TGF-beta1 could attenuate sleep in rabbits. Three doses of IL-13 (8, 40, and 200 ng) and TGF-beta1 (40, 100, and 200 ng) were injected intracerebroventricularly 3 h after the beginning of the light period. In addition, one dose of IL-13 (200 ng) and one dose of TGF-beta1 (200 ng) were injected at dark onset. The two higher doses of IL-13 and the highest dose of TGF-beta1 significantly inhibited spontanenous non-rapid eye movement sleep (NREMS) when they were given in the light period. IL-13 also inhibited NREMS after dark onset administration; however, the inhibitory effect was less potent than that observed after light period administration. The 40-ng dose of IL-13 inhibited REMS duration during the dark period. TGF-beta1 administered at dark onset had no effect on sleep. These data provide additional evidence for the hypothesis that a brain cytokine network is involved in regulation of physiological sleep.

Nuclear factor-kappaB inhibitor peptide inhibits spontaneous and interleukin-1beta-induced sleep

Nuclear factor-kappaB (NF-kappaB) is a transcription factor that when activated promotes production of several sleep-promoting substances such as interleukin-1beta (IL-1beta), tumor necrosis factor-alpha, and nerve growth factor. Therefore, we hypothesized that inhibition of NF-kappaB activation would attenuate sleep. A NF-kappaB cell-permeable inhibitor peptide (IP) was injected intracerebroventricularly (5 and 50 microg for rats, 100 microg for rabbits). On a separate day, time-matched control injections of a cell-permeable inactive control peptide were done in the same animals. The 50-microg dose of IP in rats and the 100-microg dose in rabbits significantly inhibited non-rapid eye movement sleep and rapid eye movement sleep if administered during the light period. Moreover, pretreatment of rabbits with 100 microg of the IP 12 h before intracerebroventricular injection of IL-1beta (10 ng) significantly attenuated IL-1beta-induced sleep and febrile responses. The current data support the hypothesis that a brain cytokine network is involved in sleep regulation and that NF-kappaB is a crucial factor in physiological sleep regulation.