Sleep enhances serum interleukin-7 concentrations in humans

Circadian rhythm disruption in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Implications for the post-acute sequelae of COVID-19

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a common and disabling disorder primarily characterized by persistent fatigue and exercise intolerance, with associated sleep disturbances, autonomic dysfunction, and cognitive problems. The causes of ME/CFS are not well understood but may coincide with immune and inflammatory responses following viral infections. During the current SARS-CoV2 coronavirus pandemic, ME/CFS has been increasingly reported to overlap with persistent “long COVID” symptoms, also called the post-acute sequelae of COVID-19 (PASC). Given the prominence of activity and sleep problems in ME/CFS, circadian rhythm disruption has been examined as a contributing factor in ME/CFS. While these studies of circadian rhythms have been pursued for decades, evidence linking circadian rhythms to ME/CFS remains inconclusive. A major limitation of older chronobiology studies of ME/CFS was the unavailability of modern molecular methods to study circadian rhythms and incomplete understanding of circadian rhythms outside the brain in peripheral organ systems. Major methodological and conceptual advancements in chronobiology have since been made. Over the same time, biomarker research in ME/CFS has progressed. Together, these new developments may justify renewed interest in circadian rhythm research in ME/CFS. Presently, we review ME/CFS from the perspective of circadian rhythms, covering both older and newer studies that make use of modern molecular methods. We focus on transforming growth factor beta (TGFB), a cytokine that has been previously associated with ME/CFS and has an important role in circadian rhythms, especially in peripheral cells. We propose that disrupted TGFB signaling in ME/CFS may play a role in disrupting physiological rhythms in sleep, activity, and cognition, leading to the insomnia, energy disturbances, cognition problems, depression, and autonomic dysfunction associated with ME/CFS. Since SARS-like coronavirus infections cause persistent changes in TGFB and previous coronavirus outbreaks have caused ME/CFS-like syndromes, chronobiological considerations may have immediate implications for understanding ME/CFS in the context of the COVID-19 pandemic and possibly suggest new avenues for therapeutic interventions.

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Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is characterized by ​disrupted ​sleep ​and activity ​implicating ​circadian clocks.

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The incidence of ME/CFS is expected to increase as a result of the post-acute sequelae of COVID-19.

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Biomarker studies in ME/CFS patients implicate Transforming Growth Factor B (TGFB).

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TGFB has roles in synchronizing circadian rhythms in peripheral cells.

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Identification of biomarkers and new methodologies may facilitate progress in the chronobiological basis of ME/CFS.

Sleep restriction prior to antigen exposure does not alter the T cell receptor repertoire but impairs germinal center formation during a T cell-dependent B cell response in murine spleen

It is well known that sleep promotes immune functions. In line with this, a variety of studies in animal models and humans have shown that sleep restriction following an antigen challenge dampens the immune response on several levels which leads to e.g. worsening of disease outcome and reduction of vaccination efficiency, respectively. However, the inverse scenario with sleep restriction preceding an antigen challenge is only investigated in a few animal models where it has been shown to reduce antigen uptake and presentation as well as pathogen clearance and survival rates. Here, we use injection of sheep red blood cells to investigate the yet unknown effect on a T cell-dependent B cell response in a well-established mouse model. We found that 6 ​h of sleep restriction prior to the antigen challenge does not impact the T cell reaction including the T cell receptor repertoire but dampens the development of germinal centers which correlates with reduced antigen-specific antibody titer indicating an impaired B cell response. These changes concerned a functionally more relevant level than those found in the same experimental model with the inverse scenario when sleep restriction followed the antigen challenge. Taken together, our findings showed that the outcome of the T cell-dependent B cell response is indeed impacted by sleep restriction prior to the antigen challenge which highlights the clinical significance of this scenario and the need for further investigations in humans, for example concerning the effect of sleep restriction preceding a vaccination.

Influence of the Circadian Timing System on Tacrolimus Pharmacokinetics and Pharmacodynamics After Kidney Transplantation

Introduction: Tacrolimus is the backbone immunosuppressant after solid organ transplantation. Tacrolimus has a narrow therapeutic window with large intra- and inter-patient pharmacokinetic variability leading to frequent over- and under-immunosuppression. While routine therapeutic drug monitoring (TDM) remains the standard of care, tacrolimus pharmacokinetic variability may be influenced by circadian rhythms. Our aim was to analyze tacrolimus pharmacokinetic/pharmacodynamic profiles on circadian rhythms comparing morning and night doses of a twice-daily tacrolimus formulation. Methods: This is a post-hoc analysis from a clinical trial to study the area under curve (AUC) and the area under effect (AUE) profiles of calcineurin inhibition after tacrolimus administration in twenty-five renal transplant patients. Over a period of 24 h, an intensive sampling (0, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 12.5, 13, 13.5, 14, 15, 20, and 24 h) was carried out. Whole blood and intracellular tacrolimus concentrations and calcineurin activity were measured by UHPLC-MS/MS. Results: Whole blood and intracellular AUC_12-24 h and C_max achieved after tacrolimus night dose was significantly lower than after morning dose administration (AUC_0-12 h) (p < 0.001 for both compartments). AUE_0-12 h and AUE_12-24 h were not statistically different after morning and night doses. Total tacrolimus daily exposure (AUC_0-24 h), in whole blood and intracellular compartments, was over-estimated when assessed by doubling the morning AUC_0-12 h data. Conclusion: The lower whole blood and intracellular tacrolimus concentrations after night dose might be influenced by a distinct circadian clock. This significantly lower tacrolimus exposure after night dose was not translated into a significant reduction of the pharmacodynamic effect. Our study may provide conceptual bases for better understanding the TDM of twice-daily tacrolimus formulation.

Effects of sleep on the splenic milieu in mice and the T cell receptor repertoire recruited into a T cell dependent B cell response

Sleep is known to improve immune function ranging from cell distribution in the naïve state to elevated antibody titers after an immune challenge. The underlying mechanisms still remain unclear, partially because most studies have focused on the analysis of blood only. Hence, we investigated the effects of sleep within the spleen in female C57BL/6J mice with normal sleep compared to short-term sleep-deprived animals both in the naïve state and after an antigen challenge. Lack of sleep decreased the expression of genes associated with immune cell recruitment into and antigen presentation within the spleen both in the naïve state and during a T cell dependent B cell response directed against sheep red blood cells (SRBC). However, neither T cell proliferation nor formation of SRBC-specific antibodies was affected. In addition, the T cell receptor repertoire recruited into the immune response within seven days was not influenced by sleep deprivation. Thus, sleep modulated the molecular milieu within the spleen whereas we could not detect corresponding changes in the primary immune response against SRBC. Further studies will show whether sleep influences the secondary immune response against SRBC or the development of the B cell receptor repertoire, and how this can be compared to other antigens.

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Sleep deprivation (SD) decreases expression of genes involved in T cell function.

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SD induces those changes in the milieu of both lymph nodes and spleen.

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SD dampens the expression of several genes in the spleen during an immune response.

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SD does not alter the T cell receptor repertoire recruited into the immune response.

"They can rest at home": an observational study of patients' quality of sleep in an Australian hospital

Background

Poor sleep is known to adversely affect hospital patients’ recovery and rehabilitation. The aim of the study was to investigate the perceived duration and quality of patient sleep and identify any environmental factors associated with patient-reported poor sleep in hospital.

Method

A cross-sectional study was conducted involving 15 clinical units within a 672-bed tertiary-referral hospital in Australia. Semi-structured interviews to determine perceptions of sleep quantity and quality and factors that disturb nocturnal sleep were conducted with patients and nursing staff. Environmental noise, light and temperature were monitored overnight, with concurrent logging of noise sources by observers.

Results

Patients reported a mean reduction in hospital sleep duration, compared to home, of 1.8 h (5.3 vs. 7.1 h; p < 0.001). The proportions of patients reporting their sleep quality to be poor/very poor, fair and of good quality were 41.6, 34.2 and 24.2% respectively. Patients reported poorer sleep quality than nurses (p < 0.05). Patients, nurses and observers all reported the main factors associated with poor sleep as clinical care interventions (34.3%) and environmental noise (32.1%). Noise levels in all 15 clinical areas exceeded WHO recommended levels of < 30 dB [A] by 36.7 to 82.6%, with peak noise levels of 51.3 to 103.3 dB (A).

Conclusion

Hospital in-patients are exposed to factors which reduce the duration and quality of their sleep. These extrinsic factors are potentially modifiable through behaviour change and reconfiguration of the clinical environment. The findings from this study provided the foundation for a quality improvement project currently underway to improve patients’ sleep.

Investigating the application of motion accelerometers as a sleep monitoring technique and the clinical burden of the intensive care environment on sleep quality: study protocol for a prospective observational study in Australia

INTRODUCTION

Sleep is a state of quiescence that facilitates the significant restorative processes that enhance individuals' physiological and psychological well-being. Patients admitted to the intensive care unit (ICU) experience substantial sleep disturbance. Despite the biological importance of sleep, sleep monitoring does not form part of standard clinical care for critically ill patients. There exists an unmet need to assess the feasibility and accuracy of a range of sleep assessment techniques that have the potential to allow widespread implementation of sleep monitoring in the ICU.

KEY MEASURES

The coprimary outcome measures of this study are to: determine the accuracy and feasibility of motion accelerometer monitoring (ie, actigraphy) and subjective assessments of sleep (nursing-based observations and patient self-reports) to the gold standard of sleep monitoring (ie, polysomnography) in evaluating sleep continuity and disturbance. The secondary outcome measures of the study will include: (1) the association between sleep disturbance and environmental factors (eg, noise, light and clinical interactions) and (2) to describe the sleep architecture of intensive care patients.

METHODS AND ANALYSIS

A prospective, single centre observational design with a within subjects' assessment of sleep monitoring techniques. The sample will comprise 80 adults (aged 18 years or more) inclusive of ventilated and non-ventilated patients, admitted to a tertiary ICU with a Richmond Agitation-Sedation Scale score between +2 (agitated) and -3 (moderate sedation) and an anticipated length of stay >24 hours. Patients' sleep quality, total sleep time and sleep fragmentations will be continuously monitored for 24 hours using polysomnography and actigraphy. Behavioural assessments (nursing observations) and patients' self-reports of sleep quality will be assessed during the 24-hour period using the Richards-Campbell Sleep Questionnaire, subjective sleepiness evaluated via the Karolinska Sleepiness Scale, along with a prehospital discharge survey regarding patients' perception of sleep quality and disturbing factors using the Little Sleep Questionnaire will be undertaken. Associations between sleep disturbance, noise and light levels, and the frequency of clinical interactions will also be investigated. Sound and luminance levels will be recorded at 1 s epochs via Extech SDL600 and SDL400 monitoring devices. Clinical interactions will be logged via the electronic patient record system Metavision which documents patient monitoring and clinical care.

ETHICS AND DISSEMINATION

The relevant institutions have approved the study protocol and consent procedures. The findings of the study will contribute to the understanding of sleep disturbance, and the ability to implement sleep monitoring methods within ICUs. Understanding the contribution of a clinical environment on sleep disturbance may provide insight into the need to address clinical environmental issues that may positively influence patient outcomes, and could dispel notions that the environment is a primary factor in sleep disturbance. The research findings will be disseminated via presentations at national and international conferences, proceedings and published articles in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ACTRN12615000945527; Pre-results.

Medical hypothesis: Light at night is a factor worth considering in critical care units

Exposure to light at night is not an innocuous consequence of modernization. There are compelling data linking long-term exposure to occupational and environmental light at night with serious health conditions, including heart disease, obesity, diabetes, and cancer. However, far less is known about the physiological and behavioral effects of acute exposure to light at night. Among healthy volunteers, acute night-time light exposure increases systolic blood pressure and inflammatory markers in the blood, and impairs glucose regulation. Whether critically ill patients in a hospital setting experience the same physiological shifts in response to evening light exposure is not known. This paper reviews the available data on light at night effects on health and wellbeing, and argues that the data are sufficiently compelling to warrant studies of how lighting in intensive care units may be influencing patient recovery.

Interleukin-7 Plasma Levels in Human Differentiate Anorexia Nervosa, Constitutional Thinness and Healthy Obesity

Introduction

Interleukin-7 (IL-7) is a cytokine involved in energy homeostasis as demonstrated in rodents. Anorexia nervosa is characterized by restrained eating behavior despite adaptive orexigenic regulation profile including high ghrelin plasma levels. Constitutional thinness is a physiological condition of resistance to weight gain with physiological anorexigenic profile including high Peptide YY plasma level. Healthy obesity can be considered as a physiological state of resistance to weight loss with opposite appetite regulating profile to constitutional thinness including low Peptide YY plasma level. No studies in IL-7 are yet available in those populations. Therefore we evaluated circadian plasma levels of IL-7 in anorexia nervosa compared to constitutional thinness, healthy obese and control females.

Materials and Methods

10 restrictive-type anorexia nervosa women, 5 bingeing/purging anorexia nervosa woman, 5 recovered restrictive anorexia nervosa women, 4 bulimic females, 10 constitutional thinness women, 7 healthy obese females, and 10 normal weight women controls were enrolled in this cross-sectional study, performed in endocrinology unit and academic laboratory. Twelve-point circadian profiles of plasma IL-7 levels were measured in each subject.

Results

24h mean IL-7 plasma levels (pg/ml, mean±SEM) were decreased in restrictive-type anorexia nervosa (123.4±14.4, p<0.0037), bingeing/purging anorexia nervosa (24.2±5.6, p<0.001), recovered restrictive anorexia nervosa (64.2±16.1, p = 0.01) and healthy obese patients (51±3.2, p<0.001) compared to controls (187.7±28.6). Bulimic patients (197.4±42.7) and constitutional thinness patients (264.3±35.8) were similar to controls.

Conclusions

Low IL-7 is part of the adaptive profile in restrictive-type anorexia nervosa, confirming its difference with constitutional thinness. Healthy obesity, with low IL-7, is once again in mirror image of constitutional thinness with normal high IL-7.

Sleep in the intensive care unit

Sleep is an important physiologic process, and lack of sleep is associated with a host of adverse outcomes. Basic and clinical research has documented the important role circadian rhythm plays in biologic function. Critical illness is a time of extreme vulnerability for patients, and the important role sleep may play in recovery for intensive care unit (ICU) patients is just beginning to be explored. This concise clinical review focuses on the current state of research examining sleep in critical illness. We discuss sleep and circadian rhythm abnormalities that occur in ICU patients and the challenges to measuring alterations in circadian rhythm in critical illness and review methods to measure sleep in the ICU, including polysomnography, actigraphy, and questionnaires. We discuss data on the impact of potentially modifiable disruptors to patient sleep, such as noise, light, and patient care activities, and report on potential methods to improve sleep in the setting of critical illness. Finally, we review the latest literature on sleep disturbances that persist or develop after critical illness.

Sleeping on a problem: the impact of sleep disturbance on intensive care patients - a clinical review

Sleep disturbance is commonly encountered amongst intensive care patients and has significant psychophysiological effects, which protract recovery and increases mortality. Bio-physiological monitoring of intensive care patients reveal alterations in sleep architecture, with reduced sleep quality and continuity. The etiological causes of sleep disturbance are considered to be multifactorial, although environmental stressors namely, noise, light and clinical care interactions have been frequently cited in both subjective and objective studies. As a result, interventions are targeted towards modifiable factors to ameliorate their impact. This paper reviews normal sleep physiology and the impact that sleep disturbance has on patient psychophysiological recovery, and the contribution that the clinical environment has on intensive care patients' sleep.

Sleep in the Intensive Care Unit

Patients in the intensive care unit (ICU) are susceptible to sleep deprivation. Disrupted sleep is associated with increased morbidity and mortality in the critically ill patients. The etiology of sleep disruption is multifactorial. The article reviews the literature on sleep in the ICU, the effects of sleep deprivation, and strategies to promote sleep in the ICU. Until the impact of disrupted sleep is better explained, it is appropriate to provide critically ill patients with consolidated, restorative sleep.

Rheumatoid arthritis and the biological clock

Rheumatoid arthritis (RA) is an autoimmune disease of unknown cause and a chronic and progressive inflammatory disorder ensuing in genetically predisposed subjects, characterized by synovitis causing joint destruction, as well as inflammation in body organ systems, leading to anatomical alteration and functional disability. Immune competent cells, deregulated synoviocytes and cytokines play a key role in the pathophysiological mechanisms. The immune system function shows time-related variations related to the influence of the neuroendocrine system and driven by the circadian clock circuitry. Immune processes and symptom intensity in RA are characterized by oscillations during the day following a pattern of circadian rhythmicity. A cross-talk between inflammatory and circadian pathways is involved in RA pathogenesis and underlies the mutual actions of disruption of the circadian clock circuitry on immune system function as well as of inflammation on the function of the biological clock. Modulation of molecular processes and humoral factors mediating in RA the interplay between the biological clock and the immune response and underlying the rhythmic fluctuations of pathogenic processes and symptomatology could represent a promising therapeutic strategy in the future.

Crosstalk between the circadian clock circuitry and the immune system

Various features, components, and functions of the immune system present daily variations. Immunocompetent cell counts and cytokine levels present variations according to the time of day and the sleep-wake cycle. Moreover, different immune cell types, such as macrophages, natural killer cells, and lymphocytes, contain a circadian molecular clockwork. The biological clocks intrinsic to immune cells and lymphoid organs, together with inputs from the central pacemaker of the suprachiasmatic nuclei via humoral and neural pathways, regulate the function of cells of the immune system, including their response to signals and their effector functions. Consequences of this include, for example, the daily variation in the response to an immune challenge (e.g., bacterial endotoxin injection) and the circadian control of allergic reactions. The circadian-immune connection is bidirectional, because in addition to this circadian control of immune functions, immune challenges and immune mediators (e.g., cytokines) were shown to have strong effects on circadian rhythms at the molecular, cellular, and behavioral levels. This tight crosstalk between the circadian and immune systems has wide-ranging implications for disease, as shown by the higher incidence of cancer and the exacerbation of autoimmune symptoms upon circadian disruption.

About sleep's role in memory

Over more than a century of research has established the fact that sleep benefits the retention of memory. In this review we aim to comprehensively cover the field of "sleep and memory" research by providing a historical perspective on concepts and a discussion of more recent key findings. Whereas initial theories posed a passive role for sleep enhancing memories by protecting them from interfering stimuli, current theories highlight an active role for sleep in which memories undergo a process of system consolidation during sleep. Whereas older research concentrated on the role of rapid-eye-movement (REM) sleep, recent work has revealed the importance of slow-wave sleep (SWS) for memory consolidation and also enlightened some of the underlying electrophysiological, neurochemical, and genetic mechanisms, as well as developmental aspects in these processes. Specifically, newer findings characterize sleep as a brain state optimizing memory consolidation, in opposition to the waking brain being optimized for encoding of memories. Consolidation originates from reactivation of recently encoded neuronal memory representations, which occur during SWS and transform respective representations for integration into long-term memory. Ensuing REM sleep may stabilize transformed memories. While elaborated with respect to hippocampus-dependent memories, the concept of an active redistribution of memory representations from networks serving as temporary store into long-term stores might hold also for non-hippocampus-dependent memory, and even for nonneuronal, i.e., immunological memories, giving rise to the idea that the offline consolidation of memory during sleep represents a principle of long-term memory formation established in quite different physiological systems.

Sleep loss and cytokines levels in an experimental model of psoriasis

Up to 80% of people develop a cutaneous condition closely connected to their exposure to stressful life events. Psoriasis is a chronic recurrent inflammatory skin disorder with multifactorial etiology, including genetic background, environmental factors, and immune system disturbances with a strong cytokine component. Moreover, psoriasis is variably associated with sleep disturbance and sleep deprivation. This study evaluated the influence of sleep loss in the context of an animal model of psoriasis by measuring cytokine and stress-related hormone levels. Male adult Balb/C mice with or without psoriasis were subjected to 48 h of selective paradoxical sleep deprivation (PSD). Sleep deprivation potentiated the activities of kallikrein-5 and kallikrein-7 in the skin of psoriatic groups. Also, mice with psoriasis had significant increases in specific pro-inflammatory cytokines (IL-1β, IL-6 and IL-12) and decreases in the anti-inflammatory cytokine (IL-10) after PSD, which were normalized after 48 h of sleep rebound. Linear regression showed that IL-2, IL-6 and IL-12 levels predicted 66% of corticosterone levels, which were selectively increased in psoriasis mice subject to PSD. Kallikrein-5 was also correlated with pro-inflammatory cytokines, explaining 58% of IL-6 and IL-12 variability. These data suggest that sleep deprivation plays an important role in the exacerbation of psoriasis through modulation of the immune system in the epidermal barrier. Thus, sleep loss should be considered a risk factor for the development of psoriasis.

Diurnal rhythms in blood cell populations and the effect of acute sleep deprivation in healthy young men

STUDY OBJECTIVES

The sleep/wake cycle is accompanied by changes in circulating numbers of immune cells. The goal of this study was to provide an in-depth characterization of diurnal rhythms in different blood cell populations and to investigate the effect of acute sleep deprivation on the immune system, as an indicator of the body's acute stress response.

DESIGN

Observational within-subject design.

SETTING

Home environment and Clinical Research Centre.

PARTICIPANTS

15 healthy male participants aged 23.7 ± 5.4 (standard deviation) yr.

INTERVENTIONS

Total sleep deprivation.

MEASUREMENTS AND RESULTS

Diurnal rhythms of several blood cell populations were assessed under a normal sleep/wake cycle followed by 29 hr of extended wakefulness. The effect of condition (sleep versus sleep deprivation) on peak time and amplitude was investigated. Interindividual variation of, and the level of correlation between, the different cell populations was assessed. Comprehensive nonlinear curve fitting showed significant diurnal rhythms for all blood cell types investigated, with CD4 (naïve) cells exhibiting the most robust rhythms independent of condition. For those participants exhibiting significant diurnal rhythms in blood cell populations, only the amplitude of the granulocyte rhythm was significantly reduced by sleep deprivation. Granulocytes were the most diverse population, being most strongly affected by condition, and showed the lowest correlations with any other given cell type while exhibiting the largest interindividual variation in abundance.

CONCLUSIONS

Granulocyte levels and diurnal rhythmicity are directly affected by acute sleep deprivation; these changes mirror the body's immediate immune response upon exposure to stress.

Acute sleep deprivation has no lasting effects on the human antibody titer response following a novel influenza A H1N1 virus vaccination

BACKGROUND

Experimental studies in humans have yielded evidence that adaptive immune function, including the production of antigen-specific antibodies, is distinctly impaired when sleep is deprived at the time of first antigen exposure. Here we examined the effects of a regular 24-hour sleep-wake cycle (including 8 hours of nocturnal sleep) and a 24-hour period of continuous wakefulness on the 7-week antibody production in 11 males and 13 females in response to the H1N1 (swine flu) virus vaccination. The specific antibody titer in serum was assayed by the hemagglutination inhibition test on the days 5, 10, 17, and 52 following vaccination.

RESULTS

In comparison to the sleep group, sleep-deprived males but not females had reduced serum concentration of H1N1-specific antibodies five days after vaccination, whereas antibody titers at later time points did not differ between the conditions.

CONCLUSIONS

These findings concur with the notion that sleep is a supportive influence in the very early stage of an adaptive immune response to a viral antigen. However, our results do not support the view that acute sleep deprivation has lasting effects on the human antibody titer response to influenza vaccination.

Sleep and immune function

Sleep and the circadian system exert a strong regulatory influence on immune functions. Investigations of the normal sleep–wake cycle showed that immune parameters like numbers of undifferentiated naïve T cells and the production of pro-inflammatory cytokines exhibit peaks during early nocturnal sleep whereas circulating numbers of immune cells with immediate effector functions, like cytotoxic natural killer cells, as well as anti-inflammatory cytokine activity peak during daytime wakefulness. Although it is difficult to entirely dissect the influence of sleep from that of the circadian rhythm, comparisons of the effects of nocturnal sleep with those of 24-h periods of wakefulness suggest that sleep facilitates the extravasation of T cells and their possible redistribution to lymph nodes. Moreover, such studies revealed a selectively enhancing influence of sleep on cytokines promoting the interaction between antigen presenting cells and T helper cells, like interleukin-12. Sleep on the night after experimental vaccinations against hepatitis A produced a strong and persistent increase in the number of antigen-specific Th cells and antibody titres. Together these findings indicate a specific role of sleep in the formation of immunological memory. This role appears to be associated in particular with the stage of slow wave sleep and the accompanying pro-inflammatory endocrine milieu that is hallmarked by high growth hormone and prolactin levels and low cortisol and catecholamine concentrations.

Serum IL-7 and G-CSF in major depressive disorder

Major depressive disorder (MDD) has been associated with dysregulated immune systems and impaired T cell function, but data on depression-related alterations in the levels of immunomodulatory growth factors are scarce. In order to further clarify the mechanisms underlying immune system dysregulation in depressed subjects, we examined the associations between MDD and serum levels of two immunomodulatory growth factors, interleukin (IL)-7 and granulocyte-colony stimulating factor (G-CSF), in 122 subjects (MDD with long-term symptomatology, n=61; controls, n=61). The MDD subjects had lowered levels of IL-7. In a model adjusted for age, gender and body mass index, subjects in the lowest tertile of IL-7 had a 3.4-fold increased likelihood for MDD (p=0.010). Further adjustments for sleep disturbances, alcohol use, smoking, and metabolic syndrome did not alter these findings. Moreover, the exclusion of subjects with rheumatoid arthritis, coronary heart disease, or the use of non-steroidal anti-inflammatory medications or oral corticosteroids only slightly attenuated the findings. The G-CSF levels did not differ between the two groups. The lowering of the serum levels of IL-7, a regulator of T cell homeostasis, in MDD subjects may underlie the depression-related impaired T cell function.

The regulation of central and peripheral circadian clocks in humans

Many circadian rhythms are controlled by the central clock of the suprachiasmatic nucleus of the hypothalamus, as well as clocks located in other brain regions and most peripheral tissues. These central and peripheral clocks are based on clock genes and their protein products. In recent years, the expression of clock genes has started to be investigated in human samples, primarily white blood cells, but also skin, oral mucosa, colon cells, adipose tissue as well as post-mortem brain tissue. The expression of clock genes in those peripheral tissues offers a way to monitor human peripheral clocks and to compare their function and regulation with those of the central clock, which is followed by markers such as melatonin, cortisol and core body temperature. We have recently used such an approach to compare central and peripheral rhythms in subjects under different lighting conditions. In particular, we have monitored the entrainment of the clock of blood cells in subjects undergoing a simulated night shift protocol with bright light treatment, known to efficiently reset the central clock. This line of research will be helpful for learning more about the human circadian system and to find ways to alleviate health problems of shift workers, and other populations experiencing altered circadian rhythms.

Modulating T-cell homeostasis with IL-7: preclinical and clinical studies

Interleukin-7 (IL-7) is required for the development and survival of T cells and plays a critical role in modulating T-cell homeostasis. This review will address current understanding of IL-7 biology, review recent clinical experiences and discuss potential future clinical applications of IL-7, or IL-7 blockade, in the setting of disease.

Adverse effects of sleep deprivation in the ICU

The hospital is not conducive to sleep. Patients in the ICU are particularly susceptible to sleep disruption secondary to environmental and medical issues. Despite the frequency of sleep disruption in the ICU, the quality of critically ill patients' sleep is often overlooked. This article discusses the following issues essential to understanding the factors associated with sleep loss in the ICU: (1) core elements to consider from the baseline sleep history, (2) impact of the ICU environment on the ICU patient's sleep pattern, and (3) overall systematic impact of sleep deprivation on the ICU patient.

The sleep-friendly ICU

Achieving restorative sleep in the ICU remains a challenge for most patients. Various environmental and nonenvironmental factors affect sleep patterns in the ICU. This article discusses the effects and relative importance of these factors on sleep patterns in the critical care setting. In addition, the implications of sleep pattern alteration on human physiology and homeostatic mechanisms are considered.