Cytokines in sleep regulation

Sleep fragmentation disrupts Lyme arthritis resolution in mice

STUDY OBJECTIVES

Lyme arthritis is a common late-stage complication of infection by Borrelia burgdorferi, the agent of Lyme disease. Patients with Lyme arthritis report increased levels of sleep disturbance associated with pain. Using a mouse model of experimental Lyme arthritis, we investigated the effect of disrupted sleep on the development and resolution of joint inflammation.

METHODS

Lyme arthritis-susceptible C3H/HeJ mice (n = 10/group) were infected with B. burgdorferi and were left either alone (control) or subjected to sleep fragmentation (SF). Arthritis development or resolution were monitored. The impact of SF on immune and inflammatory parameters such as arthritis severity scores, anti-borrelia antibody production, and bacterial clearance was measured. We also determined the effect of SF on arthritis resolution in C3H mice deficient in leukotriene (LT) B4 signaling (BLT1/2-/-) who display delayed Lyme arthritis resolution.

RESULTS

SF had no significant impact on Lyme arthritis development or inflammatory parameters regardless of whether SF treatment began 1 week prior to or congruent with infection. However, initiation of SF at the peak of arthritis resulted in a significant delay in arthritis resolution as measured by joint edema, arthritis severity scores, and decreased bacterial clearance from the joint. This was accompanied by significant changes in joint cytokine transcription levels (e.g., increased TNFα and decreased IL-4). SF has no significant impact on Lyme arthritis resolution in the BLT1/2-/- mice.

CONCLUSIONS

Poor sleep, especially near the peak of arthritis inflammation, may delay initiation of resolution programs possibly through altering cytokine production and host immune responses, leading to defects in spirochete clearance and prolonged disease.

The Molecular Relationship between Stress and Insomnia

The bi-directional relationship between sleep and stress has been actively researched as sleep disturbances and stress have become increasingly common in society. Interestingly, the brain and underlying neural circuits important for sleep regulation may respond uniquely to stress that leads to post-traumatic stress disorder (PTSD) and stress that does not. In stress that does not lead to PTSD, the hypothalamic-pituitary-adrenal axis (HPA) pathway is activated normally that results in sympathetic nervous system activation that allows the brain and body to return to baseline functioning. However, exposure to stress that leads to PTSD, causes enhanced negative feedback of this same pathway and results in long-term physiological and psychological changes. In this review, how stress regulates glucocorticoid signaling pathways in brain glial cells called astrocytes, and then mediates stress-induced insomnia are examined. Astrocytes are critical sleep regulatory cells and their connections to sleep and stress due to disturbed glucocorticoid signaling provide a novel mechanism to explain how stress leads to insomnia. This review will examine the interactions of stress neurobiology, astrocytes, sleep, and glucocorticoid signaling pathways and will examine the how stress that leads to PTSD and stress that does not impacts sleep-regulatory processes.

Hyperthermia and Heat Stress as Risk Factors for Sudden Infant Death Syndrome: A Narrative Review

BACKGROUND AND OBJECTIVES

Heat stress and hyperthermia are common findings in sudden infant death syndrome (SIDS) victims. It has been suggested that thermal stress can increase the risk of SIDS directly via lethal hyperthermia or indirectly by altering autonomic functions. Major changes in sleep, thermoregulation, cardiovascular function, and the emergence of circadian functions occur at the age at which the risk of SIDS peaks-explaining the greater vulnerability at this stage of development. Here, we review the literature data on (i) heat stress and hyperthermia as direct risk factors for SIDS, and (ii) the indirect effects of thermal loads on vital physiological functions.

RESULTS

Various situations leading to thermal stress (i.e., outdoors temperatures, thermal insulation from clothing and bedding, the prone position, bed-sharing, and head covering) have been analyzed. Hyperthermia mainly results from excessive clothing and bedding insulation with regard to the ambient thermal conditions. The appropriate amount of clothing and bedding thermal insulation for homeothermia requires further research. The prone position and bed-sharing do not have major thermal impacts; the elevated risk of SIDS in these situations cannot be explained solely by thermal factors. Special attention should be given to brain overheating because of the head's major role in body heat losses, heat production, and autonomic functions. Thermal stress can alter cardiovascular and respiratory functions, which in turn can lead to life-threatening events (e.g., bradycardia, apnea with blood desaturation, and glottal closure). Unfortunately, thermal load impairs the responses to these challenges by reducing chemosensitivity, arousability, and autoresuscitation. As a result, thermal load (even when not lethal directly) can interact detrimentally with vital physiological functions.

CONCLUSIONS

With the exception of excessive thermal insulation (which can lead to lethal hyperthermia), the major risk factors for SIDS appears to be associated with impairments of vital physiological functions when the infant is exposed to thermal stress.

Experimental diffuse brain injury and a model of Alzheimer's disease exhibit disease-specific changes in sleep and incongruous peripheral inflammation

Elderly populations (≥65 years old) have the highest risk of developing Alzheimer's disease (AD) and/or obtaining a traumatic brain injury (TBI). Using translational mouse models, we investigated sleep disturbances and inflammation associated with normal aging, TBI and aging, and AD. We hypothesized that aging results in marked changes in sleep compared with adult mice, and that TBI and aging would result in sleep and inflammation levels similar to AD mice. We used female 16-month-old wild-type (WT Aged) and 3xTg-AD mice, as well as a 2-month-old reference group (WT Adult), to evaluate sleep changes. WT Aged mice received diffuse TBI by midline fluid percussion, and blood was collected from both WT Aged (pre- and post-TBI) and 3xTg-AD mice to evaluate inflammation. Cognitive behavior was tested, and tissue was collected for histology. Bayesian generalized additive and mixed-effects models were used for analyses. Both normal aging and AD led to increases in sleep compared with adult mice. WT Aged mice with TBI slept substantially more, with fragmented shorter bouts, than they did pre-TBI and compared with AD mice. However, differences between WT Aged and 3xTg-AD mice in immune cell populations and plasma cytokine levels were incongruous, cognitive deficits were similar, and cumulative sleep was not predictive of inflammation or behavior for either group. Our results suggest that in similarly aged individuals, TBI immediately induces more profound sleep alterations than in AD, although both diseases likely include cognitive impairments. Unique pathological sleep pathways may exist in elderly individuals who incur TBI compared with similarly aged individuals who have AD, which may warrant disease-specific treatments in clinical settings.

Acute peripheral inflammation and post-traumatic sleep differ between sexes after experimental diffuse brain injury

Identifying differential responses between sexes following traumatic brain injury (TBI) can elucidate the mechanisms behind disease pathology. Peripheral and central inflammation in the pathophysiology of TBI can increase sleep in male rodents, but this remains untested in females. We hypothesized that diffuse TBI would increase inflammation and sleep in males more so than in females. Diffuse TBI was induced in C57BL/6J mice and serial blood samples were collected (baseline, 1, 5, 7 days post-injury [DPI]) to quantify peripheral immune cell populations and sleep regulatory cytokines. Brains and spleens were harvested at 7DPI to quantify central and peripheral immune cells, respectively. Mixed-effects regression models were used for data analysis. Female TBI mice had 77%-124% higher IL-6 levels than male TBI mice at 1 and 5DPI, whereas IL-1β and TNF-α levels were similar between sexes at all timepoints. Despite baseline sex differences in blood-measured Ly6Chigh monocytes (females had 40% more than males), TBI reduced monocytes by 67% in TBI mice at 1DPI. Male TBI mice had 31%-33% more blood-measured and 31% more spleen-measured Ly6G+ neutrophils than female TBI mice at 1 and 5DPI, and 7DPI, respectively. Compared with sham, TBI increased sleep in both sexes during the first light and dark cycles. Male TBI mice slept 11%-17% more than female TBI mice, depending on the cycle. Thus, sex and TBI interactions may alter the peripheral inflammation profile and sleep patterns, which might explain discrepancies in disease progression based on sex.

Relationships between objective sleep parameters and inflammatory biomarkers in pregnancy

We examined the relationships between sleep and inflammatory biomarkers during late pregnancy. Seventy-four women underwent an overnight sleep assessment by polysomnography. Blood samples were collected before bedtime and again within 1 h upon awakening to measure C-reactive protein (CRP), interleukin (IL)-6, and IL-6 soluble receptor. Sleep parameters included variables characterizing sleep architecture and sleep continuity. The participants were 32.2 (SD = 4.1) years old, and the average gestational age was 32.8 (3.5) weeks. Controlling for covariates, evening CRP was negatively associated with N3 sleep (β = -0.30, P = 0.010). N3 sleep was also negatively associated with morning CRP (β = -0.26, P = 0.036), with a higher percentage of N3 sleep associated with a lower level of morning CRP. Contrarily, there was a tendency for a positive association between stage N2 sleep and morning CRP (β = 0.23, P = 0.065). Stage N1 sleep was associated with morning IL-6 (β = 0.28, P = 0.021), with a higher percentage of N1 sleep associated with a higher morning IL-6. No significant associations were found between morning inflammatory biomarkers and sleep continuity parameters. In conclusion, increased light sleep was associated with increased inflammatory biomarkers, whereas more deep sleep was associated with decreased inflammatory biomarkers. These findings further support the interactions between sleep and the immune system during late pregnancy.

Sleepiness as a Local Phenomenon

Sleep occupies a third of our life and is a primary need for all animal species studied so far. Nonetheless, chronic sleep restriction is a growing source of morbidity and mortality in both developed and developing countries. Sleep loss is associated with the subjective feeling of sleepiness and with decreased performance, as well as with detrimental effects on general health, cognition, and emotions. The ideas that small brain areas can be asleep while the rest of the brain is awake and that local sleep may account for at least some of the cognitive and behavioral manifestations of sleepiness are making their way into the scientific community. We herein clarify the different ways sleep can intrude into wakefulness, summarize recent scientific advances in the field, and offer some hypotheses that help framing sleepiness as a local phenomenon.

Novel TNF receptor-1 inhibitors identified as potential therapeutic candidates for traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) begins with the application of mechanical force to the head or brain, which initiates systemic and cellular processes that are hallmarks of the disease. The pathological cascade of secondary injury processes, including inflammation, can exacerbate brain injury-induced morbidities and thus represents a plausible target for pharmaceutical therapies. We have pioneered research on post-traumatic sleep, identifying that injury-induced sleep lasting for 6 h in brain-injured mice coincides with increased cortical levels of inflammatory cytokines, including tumor necrosis factor (TNF). Here, we apply post-traumatic sleep as a physiological bio-indicator of inflammation. We hypothesized the efficacy of novel TNF receptor (TNF-R) inhibitors could be screened using post-traumatic sleep and that these novel compounds would improve functional recovery following diffuse TBI in the mouse.

METHODS

Three inhibitors of TNF-R activation were synthesized based on the structure of previously reported TNF CIAM inhibitor F002, which lodges into a defined TNFR1 cavity at the TNF-binding interface, and screened for in vitro efficacy of TNF pathway inhibition (IκB phosphorylation). Compounds were screened for in vivo efficacy in modulating post-traumatic sleep. Compounds were then tested for efficacy in improving functional recovery and verification of cellular mechanism.

RESULTS

Brain-injured mice treated with Compound 7 (C7) or SGT11 slept significantly less than those treated with vehicle, suggesting a therapeutic potential to target neuroinflammation. SGT11 restored cognitive, sensorimotor, and neurological function. C7 and SGT11 significantly decreased cortical inflammatory cytokines 3 h post-TBI.

CONCLUSIONS

Using sleep as a bio-indicator of TNF-R-dependent neuroinflammation, we identified C7 and SGT11 as potential therapeutic candidates for TBI.

Sleep duration and breast cancer prognosis: perspectives from the Women's Healthy Eating and Living Study

PURPOSE

To examine whether baseline sleep duration or changes in sleep duration are associated with breast cancer prognosis among early-stage breast cancer survivors in the multi-center Women's Healthy Eating and Living Study.

METHODS

Data were collected from 1995 to 2010. Analysis included 3047 women. Sleep duration was self-reported at baseline and follow-up intervals. Cox proportional hazard models were used to investigate whether baseline sleep duration was associated with breast cancer recurrence, breast cancer-specific mortality, and all-cause mortality. Time-varying models investigated whether changes in sleep duration were associated with breast cancer prognosis.

RESULTS

Compared to women who slept 7-8 h/night at baseline, sleeping ≥9 h/night was associated with a 48% increased risk of breast cancer recurrence (Hazard ratio [HR] 1.48, 95% Confidence interval [CI] 1.01, 2.00), a 52% increased risk of breast cancer-specific mortality (HR 1.52, 95% CI 1.09, 2.13), and a 43% greater risk of all-cause mortality (HR 1.43, 95% CI 1.07, 1.92). Time-varying models showed analogous increased risk in those who inconsistently slept ≥9 h/night (all P < 0.05), but not in those who consistently slept ≥9 h/night.

CONCLUSIONS

Consistent long or short sleep, which may reflect inter-individual variability in the need for sleep, does not appear to influence prognosis among early-stage breast cancer survivors.

Resolvins AT-D1 and E1 differentially impact functional outcome, post-traumatic sleep, and microglial activation following diffuse brain injury in the mouse

Traumatic brain injury (TBI) is induced by mechanical forces which initiate a cascade of secondary injury processes, including inflammation. Therapies which resolve the inflammatory response may promote neural repair without exacerbating the primary injury. Specific derivatives of omega-3 fatty acids loosely grouped as specialized pro-resolving lipid mediators (SPMs) and termed resolvins promote the active resolution of inflammation. In the current study, we investigate the effect of two resolvin molecules, RvE1 and AT-RvD1, on post-traumatic sleep and functional outcome following diffuse TBI through modulation of the inflammatory response. Adult, male C57BL/6 mice were injured using a midline fluid percussion injury (mFPI) model (6-10min righting reflex time for brain-injured mice). Experimental groups included mFPI administered RvE1 (100ng daily), AT-RvD1 (100ng daily), or vehicle (sterile saline) and counterbalanced with uninjured sham mice. Resolvins or saline were administered daily for seven consecutive days beginning 3days prior to TBI to evaluate proof-of-principle to improve outcome. Immediately following diffuse TBI, post-traumatic sleep was recorded for 24h post-injury. For days 1-7 post-injury, motor outcome was assessed by rotarod. Cognitive function was measured at 6days post-injury using novel object recognition (NOR). At 7days post-injury, microglial activation was quantified using immunohistochemistry for Iba-1. In the diffuse brain-injured mouse, AT-RvD1 treatment, but not RvE1, mitigated motor and cognitive deficits. RvE1 treatment significantly increased post-traumatic sleep in brain-injured mice compared to all other groups. RvE1 treated mice displayed a higher proportion of ramified microglia and lower proportion of activated rod microglia in the cortex compared to saline or AT-RvD1 treated brain-injured mice. Thus, RvE1 treatment modulated post-traumatic sleep and the inflammatory response to TBI, albeit independently of improvement in motor and cognitive outcome as seen in AT-RvD1-treated mice. This suggests AT-RvD1 may impart functional benefit through mechanisms other than resolution of inflammation alone.

Effects of an interleukin-1 receptor antagonist on human sleep, sleep-associated memory consolidation, and blood monocytes

Pro-inflammatory cytokines like interleukin-1 beta (IL-1) are major players in the interaction between the immune system and the central nervous system. Various animal studies report a sleep-promoting effect of IL-1 leading to enhanced slow wave sleep (SWS). Moreover, this cytokine was shown to affect hippocampus-dependent memory. However, the role of IL-1 in human sleep and memory is not yet understood. We administered the synthetic IL-1 receptor antagonist anakinra (IL-1ra) in healthy humans (100mg, subcutaneously, before sleep; n=16) to investigate the role of IL-1 signaling in sleep regulation and sleep-dependent declarative memory consolidation. Inasmuch monocytes have been considered a model for central nervous microglia, we monitored cytokine production in classical and non-classical blood monocytes to gain clues about how central nervous effects of IL-1ra are conveyed. Contrary to our expectation, IL-1ra increased EEG slow wave activity during SWS and non-rapid eye movement (NonREM) sleep, indicating a deepening of sleep, while sleep-associated memory consolidation remained unchanged. Moreover, IL-1ra slightly increased prolactin and reduced cortisol levels during sleep. Production of IL-1 by classical monocytes was diminished after IL-1ra. The discrepancy to findings in animal studies might reflect species differences and underlines the importance of studying cytokine effects in humans.

Inflammation-sleep interface in brain disease: TNF, insulin, orexin

The depth, pattern, timing and duration of unconsciousness, including sleep, vary greatly in inflammatory disease, and are regarded as reliable indicators of disease severity. Similarly, these indicators are applicable to the encephalopathies of sepsis, malaria, and trypanosomiasis, and to viral diseases such as influenza and AIDS. They are also applicable to sterile neuroinflammatory states, including Alzheimer’s disease, Parkinson’s disease, traumatic brain injury, stroke and type-2 diabetes, as well as in iatrogenic brain states following brain irradiation and chemotherapy. Here we make the case that the cycles of unconsciousness that constitute normal sleep, as well as its aberrations, which range from sickness behavior through daytime sleepiness to the coma of inflammatory disease states, have common origins that involve increased inflammatory cytokines and consequent insulin resistance and loss of appetite due to reduction in orexigenic activity. Orexin reduction has broad implications, which are as yet little appreciated in the chronic inflammatory conditions listed, whether they be infectious or sterile in origin. Not only is reduction in orexin levels characterized by loss of appetite, it is associated with inappropriate and excessive sleep and, when dramatic and chronic, leads to coma. Moreover, such reduction is associated with impaired cognition and a reduction in motor control. We propose that advanced understanding and appreciation of the importance of orexin as a key regulator of pathways involved in the maintenance of normal appetite, sleep patterns, cognition, and motor control may afford novel treatment opportunities.

[Prevalence and predictors of obstructive sleep apnea in patients admitted for acute myocardial infarction]

BACKGROUND

Obstructive sleep apnea has been implicated in the pathogenesis and aggravation of coronary atherosclerosis. However, it remains underdiagnosed in cardiology practice.

AIM

The aim of this study was to determine the prevalence of obstructive sleep apnea and the predictors of severe sleep apnea in patients admitted for ST elevation myocardial infarction.

METHODS

This was a prospective study which has included 120 patients hospitalized for ST elevation myocardial infarction, from April 2011 to March 2012. All patients have undergone an overnight sleep study using a portable polygraphy device, in the 15 days following the acute coronary syndrome. The diagnostic of obstructive sleep apnea was considered as apnea-hypopnea index of ≥ 5 events per hour, severe sleep apnea was defined as apnea -hypopnea index of ≥ 30. Subjective daytime sleepiness was assessed by the Epworth sleepiness scale. All patients have had an oxygen saturation monitoring in the coronary care unit using a pulse oxymeter, before undergoing the sleep study.

RESULTS

The study population was made up of 102 men and 18 women. The mean age was 58 ± 12 years. Smoking was the major cardiovascular risk factor found in 72% of all patients, diabetes and hypertension were represented in 40% and 44% of the population, respectively. Eighty-seven percent of patients were admitted in the first 24 hours of symptom onset. A primary percutaneous coronary intervention was performed in 60% of cases while fibrinolysis was done in 10% of patients. The prevalence of obstructive sleep apnea was 79%. Mean apnea-hypopnea index was 15.76 ± 14.93 and severe form was diagnosed in 16% of all patients. Multivariate analysis showed that Epworth sleepiness score of ≥ 4 and nocturnal desaturation below 82% were independent predictive factors for severe obstructive sleep apnea.

CONCLUSION

Prevalence of obstructive sleep apnea was very high in patients admitted for acute myocardial infarction. Epworth sleepiness score of ≥ 4 and nocturnal desaturation below 82% were independent predictive factors for severe form of sleep apnea.

Can high altitude influence cytokines and sleep?

The number of persons who relocate to regions of high altitude for work, pleasure, sport, or residence increases every year. It is known that the reduced supply of oxygen (O₂) induced by acute or chronic increases in altitude stimulates the body to adapt to new metabolic challenges imposed by hypoxia. Sleep can suffer partial fragmentation because of the exposure to high altitudes, and these changes have been described as one of the responsible factors for the many consequences at high altitudes. We conducted a review of the literature during the period from 1987 to 2012. This work explored the relationships among inflammation, hypoxia and sleep in the period of adaptation and examined a novel mechanism that might explain the harmful effects of altitude on sleep, involving increased Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) production from several tissues and cells, such as leukocytes and cells from skeletal muscle and brain.

The role of tumor necrosis factor-alpha and other cytokines in depression: what dermatologists should know

Recent studies have suggested that inflammatory responses may play an important role in the pathophysiology of depression. In fact, depressed individuals have been found to have higher levels of pro-inflammatory cytokines, especially tumor necrosis factor-alpha (TNF-α) and interleukin-6. This appears to be independent of any pre-existing chronic inflammatory disorders. In this article, various studies correlating increased levels of cytokines to depression are reviewed. As much as 60% of individuals with psoriasis also suffer from clinical depression. TNF-α antagonists, frequently used in the treatment of psoriasis, may be helpful in directly reducing depressive symptoms for patients with psoriasis and other chronic inflammatory conditions.

Sleep patterns in patients with acute coronary syndromes

BACKGROUND

Little is known about sleep quality in patients with acute coronary syndromes (ACS) admitted to the coronary care unit (CCU). The aim of this study was to assess nocturnal sleep in these patients, away from the CCU environment, and to evaluate potential connections with the disease process.

METHODS

Twenty-two patients with first ever ACS, who were not on sedation or inotropes, underwent a full-night polysomnography (PSG) in our sleep disorders unit within 3 days of the ACS and follow-up PSGs 1 and 6 months later.

RESULTS

PSG parameters showed a progressive improvement over the study period. There was a statistically significant increase in total sleep time (TST), sleep efficiency, slow wave sleep (SWS), and rapid eye movement (REM) sleep, while arousal index, wake after sleep onset (WASO) and sleep latency decreased. Six months after the acute event, sleep architecture was within the normal range.

CONCLUSIONS

Patients with ACS have marked alterations in sleep macro- and micro-architecture, which have a negative influence on sleep quality. The changes tend to disappear over time, suggesting a relationship with the acute phase of the underlying disease.

Cytokine mRNA induction by interleukin-1beta or tumor necrosis factor alpha in vitro and in vivo

Hypothalamic and cortical mRNA levels for cytokines such as interleukin-1beta (IL1beta), tumor necrosis factor alpha (TNFalpha), nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) are impacted by systemic treatments of IL1beta and TNFalpha. To investigate the time course of the effects of IL1beta and TNFalpha on hypothalamic and cortical cytokine gene expression, we measured mRNA levels for IL1beta, TNFalpha, interleukin-6 (IL-6), interleukin-10 (IL-10), IL1 receptor 1, BDNF, NGF, and glutamate decarboxylase-67 in vitro using hypothalamic and cortical primary cultures. IL1beta and TNFalpha mRNA levels increased significantly in a dose-dependent fashion after exposure to either IL1beta or TNFalpha. IL1beta increased IL1beta mRNA in both the hypothalamic and cortical cultures after 2-6 h while TNFalpha mRNA increased significantly within 30 min and continued to rise up to 2-6 h. Most of the other mRNAs showed significant changes independent of dose in vitro. In vivo, intracerebroventricular (icv) injection of IL1beta or TNFalpha also significantly increased IL1beta, TNFalpha and IL6 mRNA levels in the hypothalamus and cortex. IL1beta icv, but not TNFalpha, increased NGF mRNA levels in both these areas. Results support the hypothesis that centrally active doses of IL1beta and TNFalpha enhance their own mRNA levels as well as affect mRNA levels for other neuronal growth factors.

Suppressors, receptors and effects of cytokines on the aging mouse biological clock

During aging, levels of inflammatory cytokines increase and circadian rhythms are frequently altered. We here investigated neurobiological correlates of neuroinflammation and its age-related variation in the hypothalamic suprachiasmatic nucleus (SCN), the master circadian pacemaker. Day/night variations of transcripts encoding cytokine receptors and suppressors of cytokine signaling (SOCS) were correlated in groups of mice of different ages with Fos induction elicited by intracerebroventricular injections of tumor necrosis factor-alpha and interferon-gamma. Cytokine-elicited Fos induction was high at early night, when SOCS1 and SOCS3 levels were low. Such Fos induction was significantly reduced in the older SCN at early night, and paralleled by reduced expression of interferon-gamma receptor transcripts as compared to the younger SCN. In addition, Fos induction at early night exhibited marked sub-regional differences in the SCN between the age groups. The study shows that SOCS1 and SOCS3 are expressed in the biological clock with a day/night variation that may regulate SCN responsiveness to cytokine exposure, and indicates that effects of pro-inflammatory cytokines on the SCN are markedly altered during senescence.

Increased nocturnal interleukin-6 excretion in patients with primary insomnia: a pilot study

The aim of the present study was to investigate whether there is a difference in evening/nocturnal interleukin-6 (IL-6) serum excretion in patients with primary insomnia compared to controls. We hypothesized that in insomniac patients, the excretion of evening/nocturnal IL-6 is enhanced, like observed in aged adults and after sleep deprivation in healthy subjects. We studied IL-6 serum concentrations in 11 patients (two males and nine females) with primary insomnia and 11 age and gender-matched healthy controls. Sleep was monitored polysomnographically for three consecutive nights. The measurement of IL-6 (from 19:00 h to 09:00 h) in 2-h intervals were performed prior to and during the last laboratory night. Polysomnographically determined sleep parameters and subjective ratings of sleep demonstrated clear-cut impairments of sleep in the insomniac group. Nocturnal IL-6 secretion was significantly increased (p<.05) in insomniac patients for the whole measurement period (mean area under the curve+/-SD: 27.94+/-14.15 pg/ml x 2h) compared to controls (16.70+/-7.64 pg/ml x 2h). Total IL-6 secretion correlated inversely with subjectively perceived sleep quality and amount of slow wave sleep in the insomniac patients. Amount of Wake Time correlated positively with IL-6 excretion in insomniacs. The results of the present study demonstrate significantly increased nocturnal IL-6 secretion in insomniacs. It might be speculated that chronic primary insomnia with polysomnographically documented sleep impairments activates the production of IL-6 analogous to sleep deprivation studies in healthy subjects. This might also implicate a higher risk for inflammatory and cardiovascular diseases in patients with chronic insomnia.

Involvement of Ca(2+)-induced Ca2+ releasing system in interleukin-1beta-associated adenosine release

Interleukin-1beta (IL-1beta) plays an important role in neuroprotective and neurodegenerative events in the central nervous system. To clarify the mechanism of controversial actions of IL-1beta, we determined the effect of IL-1beta, as well as the interaction between IL-1beta and Ca(2+)-induced Ca2+ releasing system (CICR), on adenosine releases in mice hippocampus using mini-slices method. Basal and K(+)-stimulated adenosine releases were regulated by two types of CICRs, including inositol-1,4,5-trisphosphate (IP3) receptor and ryanodine receptor. Lower concentration of IL-1beta increased both adenosine releases, whereas higher concentration did not affect their releases. The stimulatory effect of IL-1beta on basal adenosine release was reduced by removal of extracellular Ca2+ and IP3 receptor inhibitor, while the stimulatory effect of IL-1beta on K(+)-stimulated adenosine release was reduced by ryanodine receptor inhibitor. These results suggest that the potent effect of IL-1beta upon adenosine release might contribute to the neuroprotective action of IL-1beta, whereas IL-1beta-induced neurodegeneration might be due to the overload response of Ca2+ mobilization and the inactivation of adenosine exocytosis.

Sleep-wake disturbances in people with cancer part I: an overview of sleep, sleep regulation, and effects of disease and treatment

PURPOSE/OBJECTIVES

To provide an overview of normal sleep, describe common sleep disorders, and discuss underlying sleep regulatory processes and how cancer, cancer treatment, and associated patient responses may adversely affect sleep.

DATA SOURCES

Published peer-reviewed articles and textbooks.

DATA SYNTHESIS

The duration, structure, and timing of sleep have a profound impact on health, well-being, and performance. Patients with cancer may be at risk for disturbances in sleeping and waking resulting from disease- and nondisease-related circumstances that interfere with normal sleep regulation, including demographic, lifestyle, psychological, and disease- and treatment-related factors.

CONCLUSIONS

Patients with cancer are at high risk for sleep-wake disturbances.

IMPLICATIONS FOR NURSING

An understanding of normal sleep, sleep pathology, and the factors that can precipitate sleep disturbance provides a context for nurses to interpret sleep complaints in their patients, evaluate responses to sleep-promoting interventions, and guide decision making regarding referrals.

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.

Disruption of circadian rhythms in synaptic activity of the suprachiasmatic nuclei by African trypanosomes and cytokines

Disturbances in biological rhythms pose a major disease problem, not the least in the aging population. Experimental sleeping sickness, caused by Trypanosoma brucei brucei, in rats constitutes a unique and robust chronic model for studying mechanisms of such disturbances. The spontaneous postsynaptic activity was recorded in slice preparations of the suprachiasmatic nuclei (SCN), which contain the master pacemaker for circadian rhythms in mammals, from trypanosome-infected rats. The excitatory synaptic events, which in normal rats show a daily variation, were reduced in frequency, while the inhibitory synaptic events did not significantly differ. This indicates selective disturbances in glutamate receptor-mediated neurotransmission in the SCN. Treatment with interferon-gamma in combination with lipopolysaccharide, which has synergistic actions with cytokines, and tumor necrosis factor-alpha similarly caused a reduction in excitatory synaptic SCN activity. We suggest that changes in the synaptic machinery of SCN neurons play an important pathogenetic role in sleeping sickness, and that proinflammatory cytokines can mimic these changes.

Interleukin-15 and interleukin-2 enhance non-REM sleep in rabbits

Interleukin (IL)-15 and -2 share receptor- and signal-transduction pathway (Jak-STAT pathway) components. IL-2 is somnogenic in rats but has not been tested in other species. Furthermore, the effects of IL-15 on sleep have not heretofore been described. We investigated the somnogenic actions of IL-15 in rabbits and compared them with those of IL-2. Three doses of IL-15 or -2 (10, 100, and 500 ng) were injected intracerebroventriculary at the onset of the dark period. In addition, 500 ng of IL-15 and -2 were injected 3 h after the beginning of the light period. IL-15 dose dependently increased non-rapid eye movement sleep (NREMS) and induced fever. IL-15 inhibited rapid eye movement sleep (REMS) after its administration during the light period; however, all doses of IL-15 failed to affect REMS if given at dark onset. IL-2 also dose dependently increased NREMS and fever. IL-2 inhibited REMS, and this effect was observed only in the light period. IL-15 and -2 enhanced electroencephalographic (EEG) slow waves during the initial 9-h postinjection period, then, during hours 10-23 postinjection, reduced EEG slow-wave activity. Current data support the notion that the brain cytokine network is involved in the regulation of sleep.

Changes in extracellular Ca2+ can affect the pattern of discharge in rat thalamic neurons

1. The aim of this study was to investigate some of the cellular mechanisms involved in the effects caused by changes in extracellular Ca2+ concentration ([Ca2+](o)). 2. Current- and voltage-clamp experiments were carried out on acutely isolated thalamic neurons of rats. 3. Increasing [Ca2+](o) alone induced a transition of the discharge from single spike to burst mode in isolated current-clamped neurons. 4. Increasing [Ca(2+)](o) caused the voltage-dependent characteristics of the low voltage-activated (LVA) transient Ca2+ currents to shift towards positive values on the voltage axis. Changing [Ca2+](o) from 0.5 to 5 mM caused the inactivation curve to shift by 21 mV. 5. Extracellular Ca2+ blocked a steady cationic current. This current reversed at -35 mV, was scarcely affected by Mg2+ and was completely blocked by the non-selective cation channel inhibitor gadolinium (10 microM). The effect of [Ca2+](o) was mimicked by 500 microM spermine, a polyamine which acts as an agonist for the Ca(2+)-sensing receptor, and was modulated by intracellular GTP-gamma-S. 6. At the resting potential, both the voltage shift and the block of the inward current removed the inactivation of LVA calcium channels and, together with the increase in the Ca2+ driving force, favoured a rise in the low threshold Ca2+ spikes, causing the thalamic firing to change to the oscillatory mode. 7. Our data indicate that [Ca2+](o) is involved in multiple mechanisms of control of the thalamic relay and pacemaker activity. These findings shed light on the correlation between hypercalcaemia, low frequency EEG activity and symptoms such as sleepiness and lethargy described in many clinical papers.

Experimental immunomodulation, sleep, and sleepiness in humans

Infection, inflammation, and autoimmune processes are accompanied by serious disturbances of well-being, psychosocial functioning, cognitive performance, and behavior. Here we review those studies that have investigated the effects of experimental immunomodulation on sleep and sleepiness in humans. In most of these studies bacterial endotoxin was injected intravenously to model numerous aspects of infection including the release of inflammatory cytokines. These studies show that human sleep-wake behavior is very sensitive to host defense activation. Small amounts of endotoxin, which affect neither body temperature nor neuroendocrine systems but slightly stimulate the secretion of inflammatory cytokines, promote non-rapid-eye-movement sleep amount and intensity. Febrile host responses, in contrast, go along with prominent sleep disturbances. According to present knowledge tumor necrosis factor-alpha (TNF-alpha) is most probably a key mediator of these effects, although it is likely that disturbed sleep during febrile host responses involves endocrine systems as well. There is preliminary evidence from human studies suggesting that inflammatory cytokines such as TNF-alpha not only mediate altered sleep-wake behavior during infections, but in addition are involved in physiological sleep regulation and in hypnotic effects of established sedating drugs.

Cytokines and the central nervous system

Cytokines are involved both in the immune response and in controlling various events in the central nervous system, that is, they are equally immunoregulators and modulators of neural functions and neuronal survival. On the other hand, cytokine production is under the tonic control of the peripheral and the central nervous system and the cytokine balance can be modulated by the action of neurotransmitters released from nonsynaptic varicosities [131]. The neuroimmune interactions are therefore bidirectional-cytokines and other products of the immune cells can modulate the action, differentiation, and survival of neuronal cells, while the neurotransmitter and neuropeptide release play a pivotal role in influencing the immune response. Cytokines and their receptors are constitutively expressed by and act on neurons in the central nervous system, in both its normal and its pathological state, but cytokine overexpression in the brain is an important factor in the pathogenesis of neurotoxic and neurodegenerative disorders. Accordingly, it can be accepted that the peripheral and central cytokine compartments appear to be integrated, and their effects might synergize or inhibit each other; however, it should always be taken into account that they are spatiotemporally differentially regulated. New concepts are reviewed in the regulation of relations between cytokine balance and neurodegeneration, including intracellular receptor-receptor, cell-cell, and systemic neuroimmune interactions that promote the further elucidation of the complexities and cascade of the possible interactions between cytokines and the central nervous system.

Effects of antipsychotic drugs on cytokine networks

It has been known since the 1950s that phenothiazines have immunomodulatory effects. This review summarizes recent evidence suggesting that antipsychotic drugs, in particular chlorpromazine and the atypical compound clozapine, influence the production of cytokines. Cytokines, organized in networks of related peptides with pleiotropic functions, are pivotal humoral mediators of infection and inflammation, and they play an important role in hematopoiesis and autoimmunity. Therefore, the effects of antipsychotic drugs on cytokine networks are important for the understanding of immune-mediated side effects of these drugs, e.g. agranulocytosis. In addition, modulation of cytokine production by antipsychotic agents suggests that these drugs might be useful for the treatment of diseases which primarily involve the immune system. Moreover, because cytokines are known to have numerous effects on the CNS, they may mediate effects of antipsychotic drugs on brain functions. Finally, the influence of antipsychotic drugs on cytokine networks is an important confounding factor in studies investigating disease-related immunopathology in psychiatric disorders. This review provides a synopsis of the data published on these topics and outlines future research perspectives.

Dose-dependent effects of endotoxin on human sleep

The role of the central nervous system in the host response to infection and inflammation and modulation of these responses by the hypothalamic-pituitary-adrenal system are well established. In animals, activation of host defense mechanisms increases non-rapid eye movement (NREM) sleep amount and intensity, which, in turn, are thought to support host defense, or the body's ability to defend itself against challenges to its immune system. In humans, the evidence is conflicting. Therefore, we investigated the effects of three placebo-controlled doses of endotoxin on host response, including nocturnal sleep in healthy volunteers. Administered before nocturnal sleep onset, endotoxin dose dependently increased rectal temperature, heart rate, and the plasma levels of tumor necrosis factor (TNF)-alpha, soluble TNF receptors, interleukin (IL)-1 receptor antagonist, IL-6, and cortisol. The lowest dose reliably increased circulating levels of cytokines and soluble cytokine receptors, but it did not affect rectal temperature, heart rate, or cortisol. This subtle host defense activation increased deep NREM sleep amount, often referred to as slow-wave sleep (stages 3 and 4), and intensity (delta power). Conversely, the highest dose of endotoxin disrupted sleep. Whereas it is well established that the endocrine and thermoregulatory systems are very sensitive to endotoxin, this study shows that human sleep-wake behavior is even more sensitive to activation of host defense mechanisms.

Sleep influences on homeostatic functions: implications for sudden infant death syndrome

The mechanisms underlying the sudden infant death syndrome (SIDS) appear to have origins in the fetal environment resulting in neural damage which later compromises responses to breathing or blood pressure challenges during sleep. The deficits appear to involve alterations in neurotransmitter receptors within regions involved in chemoreception and cardiovascular control. SIDS risk is enhanced by pre- and postnatal nicotine exposure, and possibly by hypoxic experiences. The prone sleeping position plays a significant role in risk, as do head positions that minimize facial escape from enclosed spaces; elevated body temperature may also be a factor. Compensatory mechanisms, including diminished gasping ability, relative failure to arouse to a safer state, or a failure to recruit respiratory efforts to overcome a blood pressure loss have been the object of recent research efforts. The findings suggest that the fatal event involves a neurally-compromised infant, circumstances that challenge vital physiology, most likely during sleep, at a particular developmental period.

Cytokine-cytokine interactions and the brain

Cytokine-cytokine interactions play a role in health and are crucial during immunological and inflammatory responses in disease. Cytokine interactions can result in additive, antagonist, or synergistic activities in maintaining physiological functions such as feeding, body temperature, and sleep, as well as in anorectic, pyrogenic, and somnogenic neurological manifestations of acute and chronic disease. These interactions involve signaling homology, convergence of signaling pathways, and/or positive or negative feedbacks within and among cytokine systems. The interplay of cytokines with neurotransmitters, peptides/neuropeptides, and hormones also influence cytokine action in the brain. Interactive chemical cascades involving cytokines are consistent with the homeostatic physiological mechanisms and with the multi-humoral, pleiotropic, and redundant processes that occur during acute and chronic disease.

The roles of IL-1, IL-6, and TNFalpha in the feeding responses to endotoxin and influenza virus infection in mice

Influenza infection or administration of bacterial endotoxin (lipopolysaccharide, LPS) results in diminished feeding and loss of body weight. It has been suggested that these effects may be mediated by cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and/or tumor necrosis factor-alpha (TNFalpha). To assess the potential role of these cytokines, we tested the ability of the naturally occurring IL-1-receptor antagonist (IL-1ra), a monoclonal antibody to mouse IL-6 (IL-6mAb), and a TNF binding protein fragment (TNFbp) to antagonize hypophagia induced by intraperitoneally (ip) injected mouse IL-1beta or LPS or by inoculation with influenza virus. Feeding was assessed by measuring the daily intake of food pellets and sweetened milk in a 30-min period. The hypophagia induced by mIL-1beta or LPS was not affected by pretreatment with IL-6mAb. The effects of IL-1beta were blocked by IL-1ra but unaffected by TNFbp. TNFbp and IL-1ra given separately both exhibited a tendency to attenuate LPS-induced hypophagia. The effectiveness of TNFbp plus IL-1ra treatment was similar to that of the individual antagonists. However, combined treatment with TNFbp, IL-1ra, and IL-6mAb almost completely prevented the depressing effect of LPS on milk intake. The antagonists were also tested in influenza virus-inoculated mice. IL-1ra was delivered chronically by osmotic minipumps and was supplemented by treatment with TNFbp and IL-6mAb. The treatments slightly attenuated the effects of the virus on milk intake 48 h after the inoculation and delayed the decrease in body weight. However, over the entire course of the experiment, the treatment produced very small, statistically nonsignificant, attenuations of the depressions in milk and food pellet intake. Similar results were obtained with TNFbp alone or the combination of IL-6mAb and TNFbp. The results suggest that IL-1beta, TNFalpha, and IL-6 contribute to the hypophagia induced by LPS. However, antagonism of all three cytokines was not sufficient to prevent the decreases in feeding and loss of body weight induced by influenza virus infection.

Sudden infant death syndrome, virus infections and cytokines

Many epidemiological risk factors identified for sudden infant death syndrome (SIDS) suggest a viral aetiology, e.g. exposure to cigarette smoke and winter peak, mild respiratory symptoms. Virus infections and bacterial toxins induce cytokine activity and it has been suggested that uncontrolled inflammatory mediators could be involved in some cases of SIDS. The aim of this review was to assess the evidence for virus infection in SIDS and to examine those findings in relation to individual variations in cytokine responses and various pathophysiological mechanisms proposed for SIDS such as sleep derangement, hypoxia, cardiac arrhythmia, vascular hypotonicity and hypoglycaemia.

Adenosine: a mediator of interleukin-1beta-induced hippocampal synaptic inhibition

Interleukin-1 (IL-1) is a pleotrophic cytokine implicated in a variety of central activities, including fever, sleep, ischemic injury, and neuromodulatory responses, such as neuroimmune, and neuroendocrine interactions. Although accumulating evidence is available regarding the expression pattern of this cytokine, its receptors in the CNS, and its mechanistic profile under pathological levels, it is unclear whether this substance modulates central neurons under physiological concentrations. Further, in light of the functional and spatial overlap between the adenosine and IL-1 systems, it is not known whether these two systems are coupled. We report here that, in rat brain slices, brief application of sub-femtomolar IL-1beta causes a profound decrease of glutamate transmission, but not GABAergic inhibition, in hippocampal CA1 pyramidal neurons. This decrease by IL-1beta is prevented by pharmacological blockade of adenosine A1 receptors. In addition, we show that IL-1beta failed to suppress glutamate transmission at room temperature. Because the production and release of adenosine in the CNS is thought to be metabolically dependent, this observation suggests that one of the functions of IL-1beta is to increase the endogenous production of adenosine. Together, these data suggest for the first time that sub-femtomolar levels of IL-1 can effectively modulate glutamate excitation in hippocampal neurons via an adenosine-dependent mechanism.

Alcohol, slow wave sleep, and the somatotropic axis

When alcohol is a large proportion of daily nutrient energy, the network of signals for energy homeostasis appears to adapt with abnormal patterns of sleep and growth hormone (GH) release along with gradual acquisition of an addictive physical dependency on alcohol. Early relapse during treatment of alcoholism is associated with a lower GH response to challenge, perhaps reflecting an altered balance of somatostatin (SS) to somatropin releasing hormone (GHRH) that also affects slow wave sleep (SWS) in dependent patients. Normal patterns of sleep have progressively shorter SWS episodes and longer rapid eye movement (REM) episodes during the overall sleep period, but the early sleep cycles of alcoholics have truncated or non-existent SWS episodes, and the longer REM episodes occur in early cycles. During SWS delta wave activity, the hypothalamus releases GHRH, which causes the pituitary to release GH. Alcohol-dependent patients have lower levels of SWS power and GH release than normal subjects, and efforts to understand the molecular basis for this maladaptation and its relation to continued alcohol dependence merit encouragement. More needs to be learned about the possibility of decreasing alcohol dependency by increasing SWS or enhancing GHRH action.

Effects of granulocyte colony-stimulating factor on night sleep in humans

Numerous animal studies suggest that cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) mediate increased sleep amount and intensity observed during infection and are, moreover, involved in physiological sleep regulation. In humans the role of cytokines in sleep-wake regulation is largely unknown. In a single-blind, placebo-controlled study, we investigated the effects of granulocyte colony-stimulating factor (G-CSF, 300 microgram sc) on the plasma levels of cytokines, soluble cytokine receptors, and hormones as well as on night sleep. G-CSF did not affect rectal temperature or the plasma levels of cortisol and growth hormone but did induce increases in the plasma levels of IL-1 receptor antagonist and both soluble TNF receptors within 2 h after injection. In parallel, the amount of slow-wave sleep and electroencephalographic delta power were reduced, indicating a lowered sleep intensity. We conclude that G-CSF suppresses sleep intensity via increased circulating amounts of endogenous antagonists of IL-1beta and TNF-alpha activity, suggesting that these cytokines are involved in human sleep regulation.

Cytokines inhibit sexual behavior in female rats: II. Prostaglandins mediate the suppressive effects of interleukin-1beta

The proinflammatory cytokine interleukin-1 (IL-1) induces several behavioral alterations that are characteristic of illness, such as anorexia and reduced locomotor and social activity. We have recently demonstrated that IL-1 inhibits sexual activity, motivation and attractivity in female, but not in male rats following either central or peripheral administration. In the present study we examined the involvement of prostaglandin (PG) synthesis in mediating IL-1-induced suppression of female sexual behavior. Administration of the cyclooxygenase blockers indomethacin or ibuprofen completely prevented IL-1-induced suppression of female sexual behavior, including the reduction in proceptive behavior, the lordosis response to a male's mounts, and the preference for a sexually active partner. In a subsequent study, ex-vivo release of hypothalamic PGE2 and the secretion of corticosterone (CS) were measured in males and estrous females following IL-1 administration. At the same time and dose of IL-1 administration that significantly reduced sexual behavior in female but not male rats, IL-1 produced a significant increase in PGE2 release in female, but not in male rats. In contrast, IL-1 induced a significant elevation of serum CS levels in males but not in females. These findings suggest that PG synthesis is involved in mediating the effects of IL-1 on female sexual behavior. Furthermore, differential secretion of PGs and CS may underlie the gender difference in the effects of IL-1 on sexual behavior.

Early physiological abnormalities after simian immunodeficiency virus infection

Central nervous system (CNS) damage and dysfunction are devastating consequences of HIV infection. Although the CNS is one of the initial targets for HIV infection, little is known about early viral-induced abnormalities that can affect CNS function. Here we report the detection of early physiological abnormalities in simian immunodeficiency virus-infected monkeys. The acute infection caused a disruption of the circadian rhythm manifested by rises in body temperature, observed in all five individuals between 1 and 2 weeks postinoculation (p.i.), accompanied by a reduction in daily motor activity to 50% of control levels. Animals remained hyperthermic at 1 and 2 months p.i. and returned to preinoculation temperatures at 3 months after viral inoculation. Although motor activity recovered to baseline values at 1 month p.i., activity levels then decreased to approximately 50% of preinoculation values over the next 2 months. Analysis of sensory-evoked responses 1 month p.i. revealed distinct infection-induced changes in auditory-evoked potential peak latencies that persisted at 3 months after viral inoculation. These early physiological abnormalities may precede the development of observable cognitive or motor deficiencies and can provide an assay to evaluate agents to prevent or alleviate neuronal dysfunction.

Neuroendocrine and immune system interactions in stress and depression

Based on the extensive characterization of communication pathways between the nervous system and the immune system, there has been increasing interest in the impact of the nervous system on the development and expression of disorders involving the immune system and the contribution of the immune system to psychiatric disease. A vast literature has documented the impact of various stressors on a wide array of immune partners, and the specific neuroendocrine pathways involved have been elucidated. The impact of cytokines on neuroendocrine function and behavior has also been determined, and the relevance of cytokines to the pathophysiology of depression has become an exciting new research frontier. This article provides a foundation for integrating neuroendocrine-immune interactions into the formulation of neuropsychiatric and immunologic disease.

Cerebrospinal fluid prostaglandins and corticotropin releasing factor in schizophrenics and controls: relationship to sleep architecture

Sleep abnormalities have been consistently observed in patients with schizophrenia. Elevated levels of corticotropin releasing factor (CRF) and prostaglandins (PGs) in the cerebrospinal fluid (CSF) of patients with schizophrenia have been reported, and these neurochemical substances, known to modulate sleep in experimental animals, may play a role in these sleep abnormalities. In this study, we measured PGD2, PGE2, PGF2alpha and CRF levels in the CSF of 14 unmedicated schizophrenic patients and 14 age- and sex-matched control subjects. Polysomnographic recordings were also carried out for each subject. As expected, the sleep of the schizophrenic subjects significantly differed from that of the controls; schizophrenic subjects had a longer sleep onset latency, slept less, spent fewer minutes in stage 2 sleep and had a lower sleep efficiency. We could not, however, detect any differences in CSF CRF and PG levels between normal and schizophrenic subjects, nor could we find any correlation between CSF variables and sleep parameters in the schizophrenic subjects and the non-psychiatric controls. These results do not favor the hypothesis of a role for CRF or PGs in the pathophysiology of sleep disturbances in schizophrenia.

Differential effects of interleukin (IL)-1beta, IL-2 and IL-6 on responding for rewarding lateral hypothalamic stimulation

Bacterial endotoxin and interleukin-1 (IL-1) challenge induce a constellation of symptoms associated with illness. While such treatment may result in anhedonia, it is often difficult to dissociate this effect from the anorexia induced by these agents, particularly in paradigms that involve appetitive motivation. The present investigation assessed the effects of several systemically administered cytokines (IL-1beta, IL-2 and IL-6) on reward processes by evaluating responding for rewarding intracranial self-stimulation (ICSS) from the lateral hypothalamus. Systemic administration of interleukin-2 (IL-2) disrupted responding from the medial forebrain bundle, and this disturbance persisted as long as 1 week following initial cytokine treatment. In contrast to reinforced responding, following IL-2 treatment, non-reinforced behavior was unaffected, indicating that the cytokine did not provoke reward-unrelated performance deficits. It was suggested that the effects of IL-2 on ICSS likely do not involve motoric, soporific, attentional or cognitive changes, but instead involve specific actions on motivational arousal. Although IL-6 was previously found to produce mesolimbic dopamine (DA) changes as marked as those induced by IL-2, systemic IL-6 treatment did not influence responding for rewarding brain stimulation. Likewise, although IL-1 at the dosage used reliably induces sickness behavior, responding for rewarding brain stimulation was unaffected. Thus it seems that anhedonia is not necessarily a component of the sickness response associated with IL-1 treatment.

The role of cytokines in the behavioral responses to endotoxin and influenza virus infection in mice: effects of acute and chronic administration of the interleukin-1-receptor antagonist (IL-1ra)

Following infection with influenza virus, animals display decreased locomotor activity and feeding behavior and loss of body weight. It has been suggested that these effects may be mediated by cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha), induced by the infection. To assess the potential role of IL-1, we tested the ability of a naturally occurring IL-1-receptor antagonist (IL-1ra) to antagonize the changes in feeding behavior induced by IL-1, endotoxin (lipopolysaccharide, LPS), and infection with influenza virus. Feeding behavior was assessed by measuring the daily intake of food pellets and sweetened milk in a 30-min period. Acute injection of IL-1 beta decreased milk intake, but mouse IL-6 and mouse TNF-alpha did not. However, TNF-alpha decreased food pellet intake slightly, especially when it was injected at the beginning of the dark phase. The reductions in milk intake induced by mouse IL-1 beta were largely prevented by IL-1ra pretreatment (100 micrograms/mouse i.p.). The LPS-induced reductions in milk intake were attenuated, but not blocked, by IL-1ra treatment (300 micrograms/mouse). LPS still induced significant decrements in the presence of the antagonist. In influenza virus-infected mice, IL-1ra was administered either by repeated subcutaneous (s.c.) injections, or by continuous s.c. infusion from osmotic minipumps. These IL-1ra treatments produced small, but statistically significant, attenuations of the depression in milk and food pellet intake in the virus-infected mice. In several experiments, IL-1ra treatment increased the survival of influenza virus-infected mice. Thus the attenuation of the hypophagia may have been caused by this IL-1ra-induced increase in survival. The results suggest that IL-1 contributes to sickness behavior induced by LPS and influenza virus infection, but it is not the only factor involved.

Soluble tumor necrosis factor receptor (p75) does not attenuate the sleep changes induced by lipopolysaccharide in the rat during the dark period

Sleep is generally enhanced during the early phase of infection. The cytokine tumor necrosis factor (TNF) has been postulated to play an important role in the acute phase sleep response. After demonstrating the ability of a soluble p75 TNF receptor (TNFR) to inhibit TNF activity in vitro, we assessed the influence of TNFR on the sleep changes evoked by lipopolysaccharide (LPS). In this vehicle-controlled experiment, 24 rats received either an intracerebroventricular injection of 10 micrograms TNFR, an intraperitoneal injection of 30 micrograms/kg LPS, or both, at the beginning of the dark period. EEG, EMG and brain temperature (Tbr) were recorded during the first 12 h post injection. Compared with vehicle, LPS had minimal effects on Tbr, but promoted non-rapid eye movement sleep (non-REMS), suppressed REMS, shortened the sleep episodes and decreased high-frequency (> or = 8 Hz) EEG activity during non-REMS. TNFR alone had no significant effects and did not attenuate any of the LPS-induced sleep changes. These results may either indicate that TNF is not critically involved in the sleep response to a low level LPS challenge during the activity phase or that the soluble p75 TNFR does not effectively antagonize the sleep changes evoked by TNF.

The biological basis of malarial disease

In this review we summarise the arguments that inflammatory cytokines, triggered by material released from the parasite at schizogony (malarial toxin), might induce the illness and pathology seen in malaria. These pro-inflammatory cytokines can generate inducible nitric oxide synthase and cause nitric oxide to be released, as can low concentrations of malarial toxin itself provided interferon-gamma, which has only low activity in the absence of malarial toxin, is present. We suggest here that recently described hypermetabolic functions of these mediators provide a much more plausible explanation for malarial hyperlactataemia and hypoglycaemia, the chief prognostic indicators in falciparum malaria, than does hypoxia secondary to mechanical blockage of vessels by sequestering parasites, which is the dominant current theory. We also review the arguments that rationalise, through these mediators, the reversibility of the coma of cerebral malaria. Although not yet tested at a cellular level, the proposal that nitric oxide generated in cerebral vascular walls contributes to this coma continues to gather indirect support. In addition, new evidence incriminating nitric oxide in the mechanism of tolerance to endotoxin rationalises the raised nitric oxide generation seen in malarial tolerance.