Tumor necrosis factor receptor fragment attenuates interferon-gamma-induced non-REM sleep in rabbits

Differential inflammatory profiles in carriers of reciprocal 22q11.2 copy number variants

BACKGROUND

Genetic copy number variants (CNVs; i.e., a deletion or duplication) at the 22q11.2 locus confer increased risk of neuropsychiatric disorders and immune dysfunction. Inflammatory profiles of 22q11.2 CNV carriers can shed light on gene-immune relationships that may be related to neuropsychiatric symptoms. However, little is known about inflammation and its relationship to clinical phenotypes in 22q11.2 CNV carriers. Here, we investigate differences in peripheral inflammatory markers in 22q11.2 CNV carriers and explore their relationship with psychosis risk symptoms and sleep disturbance.

METHODS

Blood samples and clinical assessments were collected from 22q11.2 deletion (22qDel) carriers (n=45), 22q11.2 duplication (22qDup) carriers (n=29), and typically developing (TD) control participants (n=92). Blood plasma levels of pro-inflammatory cytokines, including interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), and anti-inflammatory cytokine interleukin-10 (IL-10) were measured using a MesoScale Discovery multiplex immunoassay. Plasma levels of C-reactive protein (CRP) were measured using Enzyme-linked Immunosorbent Assay (ELISA). Linear mixed effects models controlling for age, sex, and body mass index were used to: a) examine group differences in inflammatory markers between 22qDel, 22qDup, and TD controls, b) test differences in inflammatory markers between 22qDel carriers with psychosis risk symptoms (22qDelPS+) and those without (22qDelPS-), and c) conduct an exploratory analysis testing the effect of sleep disturbance on inflammation in 22qDel and 22qDup carriers. A false discovery rate correction was used to correct for multiple comparisons.

RESULTS

22qDup carriers exhibited significantly elevated levels of IL-8 relative to TD controls (q<0.001) and marginally elevated IL-8 levels relative to 22qDel carriers (q=0.08). There were no other significant differences in inflammatory markers between the three groups (q>0.13). 22qDelPS+ exhibited increased levels of IL-8 relative to both 22qDelPS- (q=0.02) and TD controls (p=0.002). There were no relationships between sleep and inflammatory markers that survived FDR correction (q>0.14).

CONCLUSION

Our results suggest that CNVs at the 22q11.2 locus may have differential effects on inflammatory processes related to IL-8, a key mediator of inflammation produced by macrophages and microglia. Further, these IL-8-mediated inflammatory processes may be related to psychosis risk symptoms in 22qDel carriers. Additional research is required to understand the mechanisms contributing to these differential levels of IL-8 between 22q11.2 CNV carriers and IL-8's association with psychosis risk.

Bidirectional Interaction of Sepsis and Sleep Disorders: The Underlying Mechanisms and Clinical Implications

Sepsis is defined as life-threatening organ injury induced by infection, with high incidence and mortality. Sleep disorder is prevalent in septic patients and approximately 50% of patients with sepsis may develop atypical sleep patterns, but many of them may have been underdiagnosed by physicians. Sleep disorders and sepsis exhibit a close bidirectional relationship, with each condition significantly influencing the other. Conversely, sleep deprivation, sleep dysrhythmia and sleep fragmentation have been shown to impact the outcome of sepsis. This review endeavors to offer a comprehensive understanding of the intricate mechanisms that underpin the interplay between sepsis and sleep disorders, in addition to exploring potential clinical intervention strategies that could enhance outcomes for patients suffering from sepsis.

Mutual Influence Between Allergic Rhinitis and Sleep: Factors, Mechanisms, and interventions-A Narrative Review

Patients with allergic rhinitis (AR) have a high incidence of sleep disorders, such as insomnia, which can easily exacerbate nasal symptoms. The aggravation of nasal symptoms further promotes the deterioration of sleep disorders, forming a vicious cycle. Severe cases may even trigger psychological and neurological issues, such as anxiety, depression, and cognitive impairment, causing significant distress to patients, making clinical diagnosis and treatment difficult, and increasing costs. Furthermore, satisfactory therapeutics remain lacking. As the pathogenesis of AR-associated sleep disorders is not clear and research is still insufficient, paying attention to and understanding AR-related sleep disorders is crucial in clinical practice. Multiple studies have shown that the most crucial issues in current research on AR and sleep are analyzing the relationship between AR and sleep disorders, searching for the influencing factors, and investigating potential targets for diagnosis and treatment. This review aimed to identify and summarize the results of relevant studies using "AR" and "sleep disorders" as search terms. In addition, we evaluated the correlation between AR and sleep disorders and examined their interaction and potential mechanisms, offering a foundation for additional screening of potential diagnostic biomarkers and therapeutic targets.

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.

A wake-like state in vitro induced by transmembrane TNF/soluble TNF receptor reverse signaling

Tumor necrosis factor alpha (TNF) has sleep regulatory and brain development roles. TNF promotes sleep in vivo and in vitro while TNF inhibition diminishes sleep. Transmembrane (tm) TNF and the tmTNF receptors (Rs), are cleaved by tumor necrosis factor alpha convertase to produce soluble (s) TNF and sTNFRs. Reverse signaling occurs in cells expressing tmTNF upon sTNFR binding. sTNFR administration in vivo inhibits sleep, thus we hypothesized that a wake-like state in vitro would be induced by sTNFR-tmTNF reverse signaling. Somatosensory cortical neuron/glia co-cultures derived from male and female mice lacking both TNFRs (TNFRKO), or lacking TNF (TNFKO) and wildtype (WT) mice were plated onto six-well multi-electrode arrays. Daily one-hour electrophysiological recordings were taken on culture days 4 through 14. sTNFR1 (0.0, 0.3, 3, 30, 60, and 120 ng/µL) was administered on day 14. A final one-hour recording was taken on day 15. Four measures were characterized that are also used to define sleep in vivo: action potentials (APs), burstiness index (BI), synchronization of electrical activity (SYN), and slow wave power (SWP; 0.25-3.75 Hz). Development rates of these emergent electrophysiological properties increased in cells from mice lacking TNF or both TNFRs compared to cells from WT mice. Decreased SWP, after the three lowest doses (0.3, 3 and 30 ng/µL) of the sTNFR1, indicate a wake-like state in cells from TNFRKO mice. A wake-like state was also induced after 3 ng/µl sTNFR1 treatment in cells from TNFKO mice, which express the TNFR1 ligand, lymphotoxin alpha. Cells from WT mice showed no treatment effects. Results are consistent with prior studies demonstrating involvement of TNF in brain development, TNF reverse signaling, and sleep regulation in vivo. Further, the current demonstration of sTNFR1 induction of a wake-like state in vitro is consistent with the idea that small neuronal/glial circuits manifest sleep- and wake-like states analogous to those occurring in vivo. Finally, that sTNF forward signaling enhances sleep while sTNFR1 reverse signaling enhances a wake-like state is consistent with other sTNF/tmTNF/sTNFR1 brain actions having opposing activities.

Role of Glia in the Regulation of Sleep in Health and Disease

Sleep is a naturally occurring physiological state that is required to sustain physical and mental health. Traditionally viewed as strictly regulated by top-down control mechanisms, sleep is now known to also originate locally. Glial cells are emerging as important contributors to the regulation of sleep-wake cycles, locally and among dedicated neural circuits. A few pioneering studies revealed that astrocytes and microglia may influence sleep pressure, duration as well as intensity, but the precise involvement of these two glial cells in the regulation of sleep remains to be fully addressed, across contexts of health and disease. In this overview article, we will first summarize the literature pertaining to the role of astrocytes and microglia in the regulation of sleep under normal physiological conditions. Afterward, we will discuss the beneficial and deleterious consequences of glia-mediated neuroinflammation, whether it is acute, or chronic and associated with brain diseases, on the regulation of sleep. Sleep disturbances are a main comorbidity in neurodegenerative diseases, and in several brain diseases that include pain, epilepsy, and cancer. Identifying the relationships between glia-mediated neuroinflammation, sleep-wake rhythm disruption and brain diseases may have important implications for the treatment of several disorders. © 2020 American Physiological Society. Compr Physiol 10:687-712, 2020.

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.

Femtograms of Interferon-γ Suffice to Modulate the Behavior of Jurkat Cells: A New Light in Immunomodulation

Since interferon-γ (IFN-γ) tunes both innate and adaptive immune systems, it was expected to enter clinical practice as an immunomodulatory drug. However, the use of IFN-γ has been limited by its dose-dependent side effects. Low-dose medicine, which is emerging as a novel strategy to treat diseases, might circumvent this restriction. Several clinical studies have proved the efficacy of therapies with a low dose of cytokines subjected to kinetic activation, while no in vitro data are available. To fill this gap, we investigated whether low concentrations, in the femtogram range, of kinetically activated IFN-γ modulate the behavior of Jurkat cells, a widely used experimental model that has importantly contributed to the present knowledge about T cell signaling. In parallel, IFN-γ in the nanogram range was used and shown to activate Signal transducer and activator of transcription (STAT)-1 and then to induce suppressor of cytokine signaling-1 (SOCS-1), which inhibits downstream signaling. When added together, femtograms of IFN-γ interfere with the transduction cascade activated by nanograms of IFN-γ by prolonging the activation of STAT-1 through the downregulation of SOCS-1. We conclude that femtograms of IFN-γ exert an immunomodulatory action in Jurkat cells.

Long-term treatment with low-dose medicine in chronic childhood eczema: a double-blind two-stage randomized control trial

BACKGROUND

The efficacy of low-dose medicine (LDM) in childhood mild/moderate eczema is not known. We conducted a double-blind, two-stage, randomized, placebo-controlled clinical trial, lasting 23 months, to address this issue.

METHOD

Eighty children with chronic mild/moderate eczema were randomly allocated to Group A (placebo) or Group B (treatment group; Galium-Heel®, a low-dose multicomponent medicine based upon natural substances; Guna-Interleukin 12 and Guna-Interferon-γ administered twice a day for six non-consecutive months for each stage). LDM is characterized by the use of biological molecules, such as cytokines, neuropeptides, growth factors, hormones at very low concentrations, which correspond to physiological levels within the human body. The dosage of the cytokines used in this trial (IFN-γ and IL-12) is 10 fg/ml. The SCORAD index was evaluated by the same operator: subjects with a SCORAD index below 20 were considered to have mild eczema (61/80; mean: 10.79), whereas a SCORAD index between 20-50 indicated moderate eczema (19/80; mean: 26.84). The data of 66/80 children were analyzed in stage 1 and those of 62/66 children in stage 2. The primary outcome measure was reduction of eczema severity assessed by the SCORAD index. Secondary outcomes were disease-free interval, and treatment safety and tolerability.

RESULTS

The decrease in disease severity was greater in Group B than in Group A already in stage 1 (a decrease 63.9% versus 53.2%), but the difference was not significant (p = 0.16). Moreover, subjective symptoms (itching and sleep disturbances) initially decreased and then worsened in Group A, whereas itching decreased linearly and sleep disturbances decreased significantly (p=0.049) in Group B.

CONCLUSIONS

Preliminary evidence suggests potential benefit, but further work is needed to validate this approach.

TRIAL REGISTRATION

The trial was registered with EudraCT number 2010-018640-13 through the database of the National Clinical Trials Monitoring Centre Database (Osservatorio delle Sperimentazioni Cliniche, OsSC) of the Italian Medicines Agency.

Cytokine polymorphisms are associated with daytime napping in adults living with HIV

OBJECTIVE/BACKGROUND

Daytime napping longer than one hour has been associated with an increased risk for all-cause mortality. Associations between cytokine polymorphisms and daytime napping in chronic illnesses such as HIV, however, have not been well described. The purpose of this study was to examine cytokine polymorphisms associated with long daytime napping in adults living with HIV.

METHODS

A cross-sectional analysis was conducted using a convenience sample of 257 adults living with HIV. Daytime napping was assessed with wrist actigraphy data collected over three days. Participants categorized as long nappers (≥60 min) were compared to short nappers and non-nappers (<60 min). Single nucleotide polymorphisms (SNPs) for 15 candidate genes involved in cytokine signaling were analyzed. Genes included: interferon-gamma (IFNG), IFNG receptor 1 (IFNGR1), interleukins (IL1B, IL1R, IL1R2, IL2, IL4, IL6, IL8, IL10, IL13, IL17A), nuclear factors of kappa light polypeptide gene enhancer in B cells (NFKB1 and NFKB2), and tumor necrosis factor alpha (TNFA).

RESULTS

After adjusting for relevant demographic and clinical characteristics, long daytime napping was associated with 12 SNPs from seven genes: 1) IFNG rs2069728; 2) IL1B rs1143642, rs1143627, and rs16944; 3) IL2 rs2069763; 4) IL6 rs4719714, rs1554606, and rs2069845; 5) IL17A rs3819024 and rs8193036; 6) NFKB1 rs4648110; and 7) NFKB2 rs1056890.

CONCLUSIONS

Cytokine genetic variations may have a role in physiological regulation of daytime napping as well as nocturnal sleep. Cytokine polymorphisms associated with long daytime napping could help identify adults with HIV who may benefit from targeted therapeutic interventions.

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.

Interferon modulates central nervous system function

The interferons (IFNs) are an endogenous pleiotropic family of cytokines that perform fundamental physiological functions as well as protecting host organisms from disease and in maintaining homeostasis. This review covers the effects of endogenous IFN on the nervous system. It starts with the description of its receptors, followed how it modulate neuronal activity, mood, sleep, temperature, the endocrine system, the opioid system and how it regulate food consumption and the immune system. Similar to other multifunctional cytokines, an excessive or inappropriate activity of IFNs can cause toxicity and even death. Furthermore, IFNs are currently the major treatment modality for several malignant and non-malignant diseases such as chronic hepatitis C and B, multiple sclerosis, hematological malignancies, malignant melanoma, renal cell carcinoma, etc.

Sleep and body temperature responses in an acute viral infection model are altered in interferon type I receptor-deficient mice

Type I interferons (IFNs) include IFNalpha and IFNbeta, both of which are elevated in acute viral infections and both of which have been shown to induce symptoms such as fever and somnolence when administered in pharmacological doses. To investigate the role of type I IFNs in mediation of acute respiratory viral symptoms we examined sleep and body temperature responses in mice with a targeted mutation of the IFN receptor type I (IFN-RI knockouts). IFN-RI knockouts (KOs) or wild-type 129 SvEv controls were challenged intratracheally (IT) with combined poly[rI.rC] (synthetic double-stranded RNA) and IFNgamma, a model that simulates an acute viral infection with respect to body temperature and locomotor activity responses. Control mice of both strains were treated with IT IFNgamma alone. Hypothermic responses to IT poly[rI.rC]/IFNgamma were more exaggerated in the IFN-RI KO mice than in wild-type. The non-rapid eye movement sleep (NREMS) response to IT poly[rI.rC]/IFNgamma was increased earlier in the IFN-RI KO mice than in wild-type, though the total time spent in NREMS was reduced in the KOs compared to wild-type and the return to baseline NREMS was faster in the KOs. The quality of NREMS also was altered more extensively in the wild-type than in the KO mice. Spontaneous rapid eye movement sleep (REMS) was suppressed in IFN-RI KOs as previously reported, but was not substantially altered in either mouse strain by IT poly[rI.rC]/IFNgamma challenge. Our results implicate type I IFNs as inhibitors of the hypothermic response and enhancers of the NREMS response to IT poly[rI.rC]/IFNgamma, a model of acute viral infection.

Interferon and the central nervous system

Interferons (IFNs) were discovered as natural antiviral substances produced during viral infection and were initially characterized for their ability to "interfere" with viral replication, slow cell proliferation, and profound alteration of immunity. The IFNs are synthesized and secreted by monocytes, macrophages, T-lymphocytes, neurons, and glia cells. The different IFNs are classified into three classes: alpha, beta, and gamma. alpha-IFN produced in the brain exerts direct effects on the brain and endocrine system by activating the neurosecretory hypothalamic neurons and regulates the hypothalamic-pituitary-adrenocortical axis. IFNs modulate neurophysiological activities of many brain region involving in pain, temperature, and food intake regulation. alpha-IFN administration activates the sympathetic nerves innervating components of the immune system. IFNs may serve as regulatory mediators between the central nervous system, the immune system, and endocrine system. IFN is used as immunologic therapy to treat various hematologic malignancies and infectious ailments and autoimmune diseases.

The role of nitric oxide synthases in the sleep responses to tumor necrosis factor-alpha

It is well established that cytokines such as tumor necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta) are involved in physiological sleep regulation, yet their downstream somnogenic mechanisms remain largely uninvestigated. Nitric oxide (NO) is an effector molecule for some TNFalpha actions. Neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) gene knockout (KO) mice sleep differently than their respective controls. In this study, we tested the hypothesis that NO mediates TNFalpha-induced sleep using iNOS and nNOS KO mice and their corresponding wild-type controls. Systemic administration of TNFalpha increased non-rapid eye movement sleep (NREMS) in the two control strains and in the iNOS KO mice during the first 4 h post-injection but failed to increase NREMS in nNOS KO mice. Rapid eye movement sleep (REMS) was suppressed by TNFalpha in nNOS controls but not in the other strains examined. The results suggest that TNFalpha affects sleep, in part, through nNOS.

Sleep-deprived mice show altered cytokine production manifest by perturbations in serum IL-1ra, TNFa, and IL-6 levels

Serum cytokine and chemokine levels were examined in mice following 36 h of sleep deprivation, or after exposure to a known physical stressor (rotational stress). Significant changes in inflammatory cytokines/chemokines (IL-1beta, TNFalpha, IL-1ra, IL-6, and MIP-1beta, MCP-1) were observed following each manipulation, but qualitative and quantitative differences were seen. Interestingly, only physical stress was associated with measured increases in serum corticosterone levels, and with independent evidence (using in vitro immune allostimulation) for a generalized immunosuppression secondary to the experimental manipulation. Our data suggest that altered cytokine production following sleep perturbation occurs by a different mechanism from that (HPA axis) commonly attributed to stress per se.

Humoral links between sleep and the immune system: research issues

In the last twenty years we have realized that the immune system synthesizes a class of peptides, termed cytokines, that play a central role in alerting the brain to ongoing inflammation in peripheral tissues. Among the brain's responses to proinflammatory cytokines, or agents that induce these cytokines, are certain alterations in sleep profiles. Characteristically there is an increase in non-rapid eye movement sleep (NREMS), and NREMS intensity is often accompanied by a decrease in rapid eye movement sleep (REMS). Cytokines appear to play a role in normal sleep regulation; during pathology, higher levels of cytokines amplify the physiological cytokine sleep mechanisms. In this review we summarize the extensive literature on the roles of interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) in sleep regulation, and their interactions with the neuropeptides growth hormone-releasing hormone (GHRH) and corticotropin-releasing hormone (CRH). We reach the tentative conclusion that the sleep-promoting actions of IL-1 and GHRH are mediated via anterior hypothalamic neurons that are receptive to these substances. It also seems likely that TNF-alpha and CRH also influence these neurons. In addition, we discuss an array of research issues raised by these studies that remain to be resolved.

Fatigue and sleep disturbance in patients with cancer, patients with clinical depression, and community-dwelling adults

This study compared the severity of fatigue in patients with cancer to the fatigue reported by depressed psychiatric patients and community-dwelling adults. Data were collected for this study during the process of validating a new fatigue assessment tool, the Brief Fatigue Inventory (BFI). The sample included 354 cancer patients, 72 psychiatric patients, and 290 non-patient volunteers. Study subjects reported severity of fatigue and the degree to which fatigue interfered with various aspects of life. Data were also collected on sleep disturbance and demographic variables that might correlate with fatigue. The psychiatric patients reported significantly higher levels of fatigue and fatigue-related interference than the cancer patients, who reported more severe fatigue and interference than the community subjects. The sleep disturbance scores of the cancer patients and the community subjects were significantly correlated with fatigue severity. Although the majority of the psychiatric patients reported sleep disturbance, their sleep disturbance scores were not significantly associated with fatigue severity.

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.