Influence of host defense activation on sleep in humans

Sleep and Cellular Stress

Sleep is a universal phenomenon occurring in all species studied thus far. Sleep loss results in adverse physiological effects at both the organismal and cellular levels suggesting an adaptive role for sleep in the maintenance of overall health. This review examines the bidirectional relationship between sleep and cellular stress. Cellular stress in this review refers to a shift in cellular homeostasis in response to an external stressor. Studies that illustrate the fact that sleep loss induces cellular stress and those that provide evidence that cellular stress in turn promotes sleep will be discussed.

Novel concepts in sleep regulation

Knowledge regarding the cellular mechanisms of sleep regulation is accumulating rapidly. In addition to neurones, also non-neuronal brain cells (astrocytes and microglia) are emerging as potential players. New techniques, particularly optogenetics and designed receptors activated by artificial ligands (DREADD), have provided also sleep research with important additional tools to study the effect of either silencing or activating specific neuronal groups/neuronal networks by opening or shutting ion channels on cells. The advantages of these strategies are the possibility to genetically target specific cell populations and the possibility to either activate or inhibit them with inducing light signal into the brain. Studies probing circuits of NREM and REM sleep regulation, as well as their role in memory consolidation, have been conducted recently. In addition, fundamentally new thoughts and potential mechanisms have been introduced to the field. The role of non-neuronal tissues in the regulation of many brain functions has become evident. These non-neuronal cells, particularly astrocytes, integrate large number of neurones, and it has been suggested that one of their functions is to integrate the (neural) activity in larger brain areas-a feature that is one of the prominent features of also the state of sleep.

A review of the neuro- and systemic inflammatory responses in post concussion symptoms: Introduction of the "post-inflammatory brain syndrome" PIBS

Post-concussion syndrome is an aggregate of symptoms that commonly present together after head injury. These symptoms, depending on definition, include headaches, dizziness, neuropsychiatric symptoms, and cognitive impairment. However, these symptoms are common, occurring frequently in non-head injured controls, leading some to question the existence of post-concussion syndrome as a unique syndrome. Therefore, some have attempted to explain post-concussion symptoms as post-traumatic stress disorder, as they share many similar symptoms and post-traumatic stress disorder does not require head injury. This explanation falls short as patients with post-concussion syndrome do not necessarily experience many key symptoms of post-traumatic stress disorder. Therefore, other explanations must be sought to explain the prevalence of post-concussion like symptoms in non-head injury patients. Many of the situations in which post-concussion syndrome like symptoms may be experienced such as infection and post-surgery are associated with systemic inflammatory responses, and even neuroinflammation. Post-concussion syndrome itself has a significant neuroinflammatory component. In this review we examine the evidence of neuroinflammation in post-concussion syndrome and the potential role systemic inflammation plays in post-concussion syndrome like symptoms. We conclude that given the overlap between these conditions and the role of inflammation in their etiologies, a new term, post-inflammatory brain syndromes (PIBS), is necessary to describe the common outcomes of many different inflammatory insults. The concept of post-concussion syndrome is in its evolution therefore, the new term post-inflammatory brain syndromes provides a better understanding of etiology of its wide-array of symptoms and the wide array of conditions they can be seen in.

Paradoxical sleep deprivation impairs mouse survival after infection with malaria parasites

Background

Parasitic diseases like malaria are a major public health problem in many countries and disrupted sleep patterns are an increasingly common part of modern life. The aim of this study was to assess the effects of paradoxical sleep deprivation (PSD) and sleep rebound (RB) on malarial parasite infection in mice.

Methods

After PSD, one group was immediately infected with parasites (PSD). The two other PSD rebound groups were allowed to sleep normally for either 24 h (24 h RB) or 48 h (48 h RB). After the recovery periods, mice were inoculated with parasites.

Results

The PSD group was the most affected by parasites presenting the higher death rate (0.02), higher number of infected cells (p < 0.01), and decrease in body weight (p < 0.04) compared to control and 48 h RB groups. The 24 h RB group was also different from control group in survival (p < 0.03), number of infected cells (p < 0.05) and body weight (p < 0.04). After 48 hours of sleep rebound animals were allowed to restore their response to parasitic infection similar to normal sleep animals.

Conclusions

These results suggest that PSD is damaging to the immune system and leads to an increased infection severity of malaria parasites; only 48 hours of recovery sleep was sufficient to return the mice infection response to baseline values.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-015-0690-7) contains supplementary material, which is available to authorized users.

Sleep, its regulation and possible mechanisms of sleep disturbances

The state of sleep consists of different phases that proceed in successive, tightly regulated order through the night forming a physiological program, which for each individual is different but stabile from one night to another. Failure to accomplish this program results in feeling of unrefreshing sleep and tiredness in the morning. The program core is constructed by genetic factors but regulated by circadian rhythm and duration and intensity of day time brain activity. Many environmental factors modulate sleep, including stress, health status and ingestion of vigilance-affecting nutrients or medicines (e.g. caffeine). Acute sleep loss results in compromised cognitive performance, memory deficits, depressive mood and involuntary sleep episodes during the day. Moreover, prolonged sleep curtailment has many adverse health effects, as evidenced by both epidemiological and experimental studies. These effects include increased risk for depression, type II diabetes, obesity and cardiovascular diseases. In addition to voluntary restriction of sleep, shift work, irregular working hours, jet lag and stress are important factors that induce curtailed or bad quality sleep and/or insomnia. This review covers the current theories on the function of normal sleep and describes current knowledge on the physiologic effects of sleep loss. It provides insights into the basic mechanisms of the regulation of wakefulness and sleep creating a theoretical background for understanding different disturbances of sleep.

Brain-specific interleukin-1 receptor accessory protein in sleep regulation

Interleukin (IL)-1β is involved in several brain functions, including sleep regulation. It promotes non-rapid eye movement (NREM) sleep via the IL-1 type I receptor. IL-1β/IL-1 receptor complex signaling requires adaptor proteins, e.g., the IL-1 receptor brain-specific accessory protein (AcPb). We have cloned and characterized rat AcPb, which shares substantial homologies with mouse AcPb and, compared with AcP, is preferentially expressed in the brain. Furthermore, rat somatosensory cortex AcPb mRNA varied across the day with sleep propensity, increased after sleep deprivation, and was induced by somnogenic doses of IL-1β. Duration of NREM sleep was slightly shorter and duration of REM sleep was slightly longer in AcPb knockout than wild-type mice. In response to lipopolysaccharide, which is used to induce IL-1β, sleep responses were exaggerated in AcPb knockout mice, suggesting that, in normal mice, inflammation-mediated sleep responses are attenuated by AcPb. We conclude that AcPb has a role in sleep responses to inflammatory stimuli and, possibly, in physiological sleep regulation.

Chronic interferon-alpha administration disrupts sleep continuity and depth in patients with hepatitis C: association with fatigue, motor slowing, and increased evening cortisol

BACKGROUND

Consequences of chronic exposure to cytokines of the innate immune system on sleep in humans and the association of cytokine-induced sleep alterations with behavior, motor performance, and cortisol secretion are unknown.

METHODS

Thirty-one patients with hepatitis C without pre-existing sleep disorders underwent nighttime polysomnography, daytime multiple sleep latency testing, behavioral assessments, neuropsychological testing, and serial blood sampling at baseline and after ∼12 weeks of either treatment with the innate immune cytokine interferon (IFN)-alpha (n = 19) or no treatment (n = 12). Fatigue and sleepiness were assessed using the Multidimensional Fatigue Inventory and Epworth Sleepiness Scale.

RESULTS

Interferon-alpha administration led to significant increases in wake after sleep onset and significant decreases in stage 3/4 sleep and sleep efficiency. Rapid eye movement latency and stage 2 sleep were significantly increased during IFN-alpha treatment. Decreases in stage 3/4 sleep and increases in rapid eye movement latency were associated with increases in fatigue, whereas decreases in sleep efficiency were associated with reduced motor speed. Increased wake after sleep onset was associated with increased evening plasma cortisol. Despite IFN-alpha-induced increases in fatigue, daytime sleepiness did not increase. In fact, IFN-alpha-treated patients exhibited decreased propensity to fall asleep during daytime nap opportunities.

CONCLUSIONS

Chronic exposure to an innate immune cytokine reduced sleep continuity and depth and induced a sleep pattern consistent with insomnia and hyperarousal. These data suggest that innate immune cytokines may provide a mechanistic link between disorders associated with chronic inflammation, including medical and/or psychiatric illnesses and insomnia, which, in turn, is associated with fatigue, motor slowing, and altered cortisol.

Abnormal sleep-wake cycles in patients with tuberculous meningitis: a case-control study

BACKGROUND

Patients with tuberculous meningitis (TBM) have been frequently observed to have excessive sleep during the day and frequent awakenings during night. We undertook this study to evaluate sleep related abnormalities in patients with TBM since there is no published literature pertaining to the same.

AIMS AND OBJECTIVES

To study sleep wake cycles in patients with tuberculous meningitis by actigraphy and sleep logs and compare these with age and sex matched controls.

METHODS

Consecutive patients admitted with tuberculous meningitis were studied clinically and with three days of continuous wrist actigraphy and sleep/wake parameters were compared to those of age and gender matched normal healthy controls.

RESULTS

Forty three patients with tuberculous meningitis were enrolled in the study. Of these, twenty-eight patients (15 females, 13 males; mean age 31.64 years) who were able to complete adequate actigraphy were compared with an equal number of controls (15 females, 13 males; mean age 30.93 years). Patients were found to have greater sleep time (p<0.0005) and more sleep episodes (p<0.0005) during the day while during the night they had less sleep (p<0.0005) with more frequent (p=0.019) and longer (p<0.0005) awakenings as compared to normal controls. Majority of the patients had reversal of sleep/wake cycles. There was poor co-relation between sleep parameters measured by actigraphy and sleep logs.

CONCLUSIONS

Tuberculous meningitis is associated with significant alteration of sleep-wake circadian cycles. This needs to be further characterized through studies involving polysomnography. There is a need to address these specific sleep difficulties to improve the quality of life of the patient as well as the care-giver.

Characterization of the melanin-concentrating hormone neurons activated during paradoxical sleep hypersomnia in rats

Although the main nodes of the neuronal network that regulate paradoxical sleep (PS), also called rapid eye movement sleep, have been identified in rodents, it still needs to be more thoroughly described. We have recently shown that 58% of a hypothalamic neuronal population, the melanin-concentrating hormone (MCH) neurons, are activated after a PS hypersomnia and that MCH, when injected intracerebroventricularly, induces a dose-dependent increase in PS. This suggests that MCH plays a role in PS regulation. Two subpopulations of MCH neurons have been distinguished neurochemically, one that coexpresses cocaine and amphetamine-regulated transcript (CART) and sends ascending projections to the septum and the hippocampus, the other, the non-CART MCH neurons, send descending projections to the lower brainstem and the spinal cord. In order to better characterize the PS-activated MCH neurons it is interesting to determine whether they belong to the first, the second, or both subgroups. We therefore undertook an MCH, CART, and Fos triple immunolabeling study in PS hypersomniac rats. We showed that the MCH neurons activated during PS are part of both subpopulations since we found CART and non-CART MCH-activated neurons. Based on these results and the literature, we propose that MCH could be involved in memory processes and in the inhibition of muscle tone during PS.

Sleep disorders are long-term sequelae of both bacterial and viral meningitis

BACKGROUND

Many bacterial meningitis patients experience neurological or neuropsychological sequelae, predominantly deficits in short-term memory, learning, and attention. Neuropsychological symptoms after viral meningitis are observed less frequently. Sleep disturbance has been reported after both viral and bacterial meningitis.

OBJECTIVES

To examine systematically the frequency and extent of sleep disturbance in meningitis patients.

METHODS

Eighty six viral or bacterial meningitis (onset of acute disease at least 1 year previously) patients were examined using two standardised questionnaires (Schlaffragebogen B and the Pittsburgh Sleep Quality Index, PSQI) in conjunction with a standardised neurological examination, and compared to a control group of 42 healthy age-matched volunteers.

RESULTS

Patients after both viral and bacterial meningitis described their sleep as reduced in quality and less restful than that of healthy control subjects; both patient groups had a pathological mean PSQI total score. Impaired sleep scores after meningitis were not correlated to either the Glasgow Coma Scale or the Glasgow Outcome Scale. Moreover, no relationship between residual neurological dysfunction or depressivity and sleep quality was observed.

CONCLUSIONS

Impaired sleep is a long-term consequence of meningitis. Additional, so far undetermined, factors other than the severity of concomitant neurological deficits are responsible for the development of this sequela.

Sleep quality and health-related quality of life in HIV-infected African-American women of childbearing age

A descriptive, correlational design was used to examine the associations of sleep quality and stage of illness with health-related quality of life (HRQOL) in HIV-infected African-American women. Participants were recruited from 12 health clinics and AIDS service organizations (ASO) in Georgia, North Carolina, and South Carolina. The sample consisted of 144 African-American women who ranged in age from 20 to 48 years (m = 34.8, SD = 6.8). The Pittsburgh Sleep Quality Index (PSQI) and the Medical Outcomes Short-Form Health Survey (SF-36) were administered. Participants were categorized as good sleepers (PSQI global score < 7) or poor sleepers (PSQI global score > or = 7) using the median global sleep quality score. Differences in HRQOL between good and poor sleepers, as measured by the SF-36, were tested using MANOVA. Good sleepers scored significantly higher (p < 0.0001) for each SF-36 quality of life dimension and the mental and physical health summary scores. Multiple regression analysis indicated that sleep quality is associated with HRQOL, independent of the individual's stage of illness, more so with mental HRQOL than with physical HRQOL. The results suggest that treatment for poor sleep quality should be a primary concern for the treatment of HIV infection and a means for improving HRQOL.

Management of insomnia in patients with chronic pain conditions

The management of insomnia in patients experiencing chronic pain requires careful evaluation, good diagnostic skills, familiarity with cognitive-behavioural interventions and a sound knowledge of pharmacological treatments. Sleep disorders are characterised by a circular interrelationship with chronic pain such that pain leads to sleep disorders and sleep disorders increase the perception of pain. Sleep disorders in individuals with chronic pain remain under-reported, under-diagnosed and under-treated, which may lead--together with the individual's emotional, cognitive and behavioural maladaptive responses--to the frequent development of chronic sleep disorders. The moderately positive relationship between pain severity and sleep complaints, and the specificity of pain-related arousal and mediating variables such as depression, illustrate that insomnia in relation to chronic pain is multifaceted and poorly understood. This may explain the limited success of the available treatments. This article discusses the evaluation of patients with chronic pain and insomnia and the available pharmacological and nonpharmacological interventions to manage the sleep disorder. Non-pharmacological interventions should not be considered as single interventions, but in association with one another. Some non-pharmacological interventions especially the cognitive and behavioural approaches, can be easily implemented in general practice (e.g. stimulus control, sleep restriction, imagery training and progressive muscle relaxation). Hypnotics are routinely prescribed in the medically ill, regardless of their adverse effects; however, their long-term efficacy is not supported by robust evidence. Antidepressants provide an interesting alternative to hypnotics, since they can improve pain perception as well as sleep disorders in selected patients. Sedative antipsychotics can be considered for sleep disturbances in those patients exhibiting psychotic features, or for those with contraindications to benzodiazepines. Low doses of sedative antipsychotics may improve chronic insomnia in the elderly. However, no intervention is likely to be effective unless a good physician-patient relationship is developed.

THEGENETICS OFNARCOLEPSY

Human narcolepsy is a genetically complex disorder. Family studies indicate a 20-40 times increased risk of narcolepsy in first-degree relatives and twin studies suggest that nongenetic factors also play a role. The tight association between narcolepsy-cataplexy and the HLA allele DQB1*0602 suggests that narcolepsy has an autoimmune etiology. In recent years, extensive genetic studies in animals, using positional cloning in dogs and gene knockouts in mice, have identified abnormalities in hypothalamic hypocretin (orexin) neurotransmission as key to narcolepsy pathophysiology. Though most patients with narcolepsy-cataplexy are hypocretin deficient, mutations or polymorphisms in hypocretin-related genes are extremely rare. It is anticipated that susceptibility genes that are independent of HLA and impinge on the hypocretin neurotransmitter system are isolated in human narcolepsy.

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.

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.

Alterations of host defence system after sleep deprivation are followed by impaired mood and psychosocial functioning

In healthy humans, sleep deprivation (SD) has consistently been demonstrated to impair different parameters of the host defence system and of psychosocial functioning. However, the individual timing of these alterations and their possible association have remained unknown so far. We therefore investigated functional measures of the individual host defence system as well as of subjective well-being and psychosocial performance in 10 healthy male adults before and after SD, as well as after recovery sleep. In detail, we examined the number of leukocytes, granulocytes, monocytes, lymphocytes, B cells, T cells, T helper and cytotoxic T cells, natural killer (NK) cells as well as the interleukin-1 beta (IL-1 beta) release from platelets after serotonin (5-HT) stimulation. Mood and psychosocial performance (excitement, energy, ability to work and timidity) were measured by visual analogue scales. Taken together, SD induced a deterioration of both mood and ability to work, which was most prominent in the evening after SD, while the maximal alterations of the host defence system could be found twelve hours earlier, i.e., already in the morning following SD. Our findings therefore suggest an SD-induced alteration of these psychoimmune response patterns in healthy humans preceding deterioration of mood and psychosocial functioning.

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.

Understanding cytokines. Part I: Physiology and mechanism of action

This is the first of a 2-part article on understanding cytokines. Cytokines are intercellular signaling proteins released from virtually all nucleated cells that influence growth and cellular proliferation in a wide range of tissues. Cytokines have immune modulating effects and are understood to control most of the physical and psychological symptoms associated with infection and inflammation. Cytokines also influence reproduction and bone remodeling. Dysregulation of the cytokine cellular system has significant implications in the development of a variety of illnesses, including most autoimmune disorders, many diseases of the cardiovascular system, osteoporosis, asthma, and depression. For nurses to be adequately informed when caring for clients with chronic illnesses and to be sufficiently knowledgeable when evaluating client outcomes, an understanding of the physiology of cytokines, the occurrences of dysregulation, and the role of cytokines in health and illness is essential. In Part I of this review, cytokine physiology is presented, with an emphasis on characteristics, categories, and mechanism of action. Specific instances of cytokine function in health and disease and implications for nursing research and practice are presented in Part II.

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.

Plasma levels of cytokines and soluble cytokine receptors in psychiatric patients upon hospital admission: effects of confounding factors and diagnosis

It has been hypothesized that the immune system plays a pathogenetic role in psychiatric disorders, in particular in major depression and schizophrenia. This hypothesis is supported by a number of reports on altered circulating levels and in vitro production of cytokines in these disorders. However, the respective evidence is not consistent. This may be in part due to an incomplete control for numerous confounding influences in earlier studies. We investigated the plasma levels of cytokines and soluble cytokine receptors in psychiatric patients (N = 361) upon hospital admission and compared the results to those obtained in healthy controls (N = 64). By multiple regression analysis we found that circulating levels of interleukin-1 receptor antagonist (IL-1Ra), soluble IL-2 receptor (sIL-2R), tumor necrosis factor-alpha (TNF-alpha), soluble TNF receptors (sTNF-R p55, sTNF-R p75) and IL-6 were significantly affected by age, the body mass index (BMI), gender, smoking habits, ongoing or recent infectious diseases, or prior medication. Cytokine or cytokine receptor levels were significantly increased in patients treated with clozapine (sIL-2R, sTNF-R p75), lithium (TNF-alpha, sTNF-R p75, IL-6) or benzodiazepines (TNF-alpha, sTNF-R p75). Taking all these confounding factors into account, we found no evidence for disease-related alterations in the levels of IL-1Ra, sIL-2R, sTNF-R p75 and IL-6, whereas levels of TNF-alpha and sTNF-R p55 in major depression and sTNF-R p55 in schizophrenia were slightly decreased compared to healthy controls. We conclude that, if confounding factors are carefully taken into account, plasma levels of the above mentioned cytokines and cytokine receptors yield little, if any, evidence for immunopathology in schizophrenia or major depression.

Effects of clozapine on sleep: a longitudinal study

Polysomnographic studies on the effects of clozapine, an atypical antipsychotic agent with strong sedative properties, on night sleep report inconsistent results. Most of these studies did not include baseline recordings and were not controlled for clozapine-induced fever, which is known to alter nocturnal sleep. We conducted a 2-week longitudinal polysomnographic investigation in 10 long-term drug-free schizophrenic patients prior to and at the end of the first and second weeks of clozapine treatment. Rectal temperature was measured daily and patients with fever (> 37.9 degrees C) were excluded. Clozapine significantly improved sleep continuity. In addition, non-rapid eye movement (NREM) sleep and in particular stage 2 sleep increased significantly, while the amounts of stage 4 and slow-wave sleep decreased significantly. Clozapine increased significantly REM density, but it did not affect the amount of REM sleep. We conclude that in patients who do not experience clozapine-induced fever, clozapine has strong sleep consolidating effects resulting from an increase in stage 2 NREM sleep.