Phagocyte migration and cellular stress induced in liver, lung, and intestine during sleep loss and sleep recovery

Effects of Obstructive Sleep Apnea on Airway Immunity and Susceptibility to Respiratory Infections

Obstructive sleep apnea is a prevalent sleep disorder characterized by recurrent episodes of partial or complete upper airway collapse during sleep, leading to disrupted breathing patterns and intermittent hypoxia. OSA results in systemic inflammation but also directly affects the upper and lower airways leading to upregulation of inflammatory pathways and alterations of the local microbiome. These changes result in increased susceptibility to respiratory infections such as influenza, COVID-19, and bacterial pneumonia. This relationship is more complex and bidirectional in individuals with chronic lung disease such as chronic obstructive lung disease, interstitial lung disease and bronchiectasis.

Overlaps between obstructive sleep apnoea and other respiratory diseases, including COPD, asthma and interstitial lung disease

In the past, there was limited research relating to the role of sleep in respiratory diseases. Physicians treating these patients tended to focus mainly on the daily disabling symptoms, overlooking the possible significant role of coexisting sleep disorders such as obstructive sleep apnoea (OSA). Nowadays, OSA has been recognised as an important, highly prevalent comorbidity for respiratory diseases such as COPD, asthma and interstitial lung diseases (ILDs). Overlap syndrome refers to the coexistence of chronic respiratory disease and OSA in the same patient. Although, in the past, overlap syndromes have been poorly studied, recent data underline that they result in increased morbidity and mortality compared with either underlying disorder alone. OSA and respiratory disease may be of different severity, and this, along with the existence of various clinical phenotypes, points to the necessity of an individualised therapeutic plan. Early recognition and OSA management could offer key benefits, such as improved sleep, quality of life and disease outcomes.

Educational aims

Describe pathophysiological aspects of OSA in chronic respiratory diseases such as COPD, asthma and ILDs.Understand the bidirectional clinical importance when OSA coexists in chronic respiratory diseases.Review current knowledge of treatment strategies towards an individualised therapeutic plan resulting in patient-centric outcomes.

A Potential Role of Keratinocyte-Derived Bilirubin in Human Skin Yellowness and Its Amelioration by Sucrose Laurate/Dilaurate

Sallow and/or dull skin appearance is greatly attributable to the yellow components of skin tone. Bilirubin is a yellow chromophore known to be made in the liver and/or spleen and is transported throughout the body via the blood stream. Recent publications suggest bilirubin may be synthesized in other cells/organs, including the skin. We found human keratinocytes express the transcripts involved in bilirubin biosynthesis. In parallel, we also found human keratinocytes could indeed synthesize bilirubin in monolayer keratinocytes and in a 3D human skin-equivalent model. The synthesized amount was substantial enough to contribute to skin yellowness. In addition, oxidative stress enhanced bilirubin production. Using UnaG, a protein that forms a fluorescent species upon binding to bilirubin, we also visualized the intracellular expression of bilirubin in keratinocytes. Finally, we screened a compound library and discovered that the sucrose laurate/dilaurate (SDL) combination significantly reduced bilirubin levels, as well as bilirubin-mediated yellowness. In conclusion, bilirubin is indeed synthesized in epidermal keratinocytes and can be upregulated by oxidative stress, which could contribute to chronic or transient yellow skin tone appearance. Application of SDL diminishes bilirubin generation and may be a potential solution to mitigate yellowish and/or dull skin appearance.

Asthma and Obstructive Sleep Apnea Overlap: What Has the Evidence Taught Us?

Obstructive sleep apnea (OSA) and asthma are highly prevalent chronic respiratory disorders. Beyond their frequent coexistence arising from their high prevalence and shared risk factors, these disorders feature a reciprocal interaction whereby each disease impacts the severity of the other. Emerging evidence implicates airway and systemic inflammation, neuroimmune interactions, and effects of asthma-controlling medications (corticosteroids) as factors that predispose patients with asthma to OSA. Conversely, undiagnosed or inadequately treated OSA adversely affects asthma control, partly via effects of intermittent hypoxia on airway inflammation and tissue remodeling. In this article, we review multiple lines of recently published evidence supporting this interaction. We provide a set of recommendations for clinicians involved in the care of adults with asthma, and identify critical gaps in our knowledge about this overlap.

Sleep enhances numbers and function of monocytes and improves bacterial infection outcome in mice

Sleep strongly impacts both humoral and cellular immunity; however, its acute effects on the innate immune defense against pathogens are unclear. Here, we elucidated in mice whether sleep affects the numbers and functions of innate immune cells and their defense against systemic bacterial infection. Sleep significantly increased numbers of classical monocytes in blood and spleen of mice that were allowed to sleep for six hours at the beginning of the normal resting phase compared to mice kept awake for the same time. The sleep-induced effect on classical monocytes was neither caused by alterations in corticosterone nor myelopoiesis, bone marrow egress or death of monocytes and did only partially involve Gαi-protein coupled receptors like chemokine receptor 2 (CCR2), but not the adhesion molecules intercellular adhesion molecule 1 (ICAM-1) or lymphocyte function-associated antigen 1 (LFA-1). Notably, sleep suppressed the expression of the clock gene Arntl in splenic monocytes and the sleep-induced increase in circulating classical monocytes was abrogated in Arntl-deficient animals, indicating that sleep is a prerequisite for clock-gene driven rhythmic trafficking of classical monocytes. Sleep also enhanced the production of reactive oxygen species by monocytes and neutrophils. Moreover, sleep profoundly reduced bacterial load in blood and spleen of mice that were allowed to sleep before systemic bacterial infection and consequently increased survival upon infection. These data provide the first evidence that sleep enhances numbers and function of innate immune cells and therewith strengthens early defense against bacterial pathogens.

The relationship between obstructive sleep apnea syndrome and obesity: A new perspective on the pathogenesis in terms of organ crosstalk

INTRODUCTION

Obstructive sleep apnea syndrome (OSAS) is a common disorder that has a major impact on public health. The connection between OSAS and obesity is very complex and likely represents an interaction between biological and lifestyle factors. Oxidative stress, inflammation and metabolic dysregulation are both actors involved in the pathogenesis of OSAS and obesity. Also, the current evidence suggests that gut microbiota plays a significant role in the emergence and progression of some metabolic disorders. When the relationship between OSAS and obesity is evaluated extensively, it is understood that they show mutual causality with each other, and that metabolic challenges such as impaired microbiota affect this bidirectional organ interaction, and by ensuing organ injury.

OBJECTIVES

The aim of this study is to investigate the association between OSAS and obesity, and the effect of "organ crosstalk" on the pathogenesis of the relationship and to contribute to the diagnosis and treatment options in the light of current data.

DATA SOURCE

We performed an electronic database search including PubMed, EMBASE and Web of Science. We used the following search terms: OSAS, obesity, inflammation, metabolic dysregulation and gut microbiota.

CONCLUSION

Obesity and OSAS adversely affect many organs and systems. Besides the factors affecting the diagnosis of the OSAS-obesity relationship, mutual organ interactions among the respiratory system, adipose tissue and intestines should not be ignored for prevention and treatment of OSAS and obesity. Comprehensive clinical trials addressing the efficacy and efficiency of current or potential treatments on therapeutic applications in the OSAS-obesity relationship are needed.

Insights into paradoxical (REM) sleep homeostatic regulation in mice using an innovative automated sleep deprivation method

Identifying the precise neuronal networks activated during paradoxical sleep (PS, also called REM sleep) has been a challenge since its discovery. Similarly, our understanding of the homeostatic mechanisms regulating PS, whether through external modulation by circadian and ultradian drives or via intrinsic homeostatic regulation, is still limited, largely due to interfering factors rendering the investigation difficult. Indeed, none of the studies published so far were able to manipulate PS without significantly altering slow-wave sleep and/or stress level, thus introducing a potential bias in the analyses. With the aim of achieving a better understanding of PS homeostasis, we developed a new method based on automated scoring of vigilance states—using electroencephalogram and electromyogram features—and which involves closed-loop PS deprivation through the induction of cage floor movements when PS is detected. Vigilance states were analyzed during 6 and 48 h of PS deprivation as well as their following recovery periods. Using this new automated methodology, we were able to deprive mice of PS with high efficiency and specificity, for short or longer periods of time, observing no sign of stress (as evaluated by plasma corticosterone level and sleep latency) and requiring no human intervention or environmental changes. We show here that PS can be homeostatically modulated and regulated while no significant changes are induced on slow-wave sleep and wakefulness, with a PS rebound duration depending on the amount of prior PS deficit. We also show that PS interval duration is not correlated with prior PS episode duration in the context of recovery from PS deprivation.

Sleep and body temperature in TNFα knockout mice: The effects of sleep deprivation, β3-AR stimulation and exogenous TNFα

Increased production of pro-inflammatory cytokines is assumed to mediate increased sleep under inflammatory conditions, such as systemic infections or recovery from sleep loss. The role of cytokines in sleep regulation under normal conditions is less clear. In the present study, we investigated the role of endogenous tumor necrosis factor alpha (TNFα) in sleep regulation using TNFα knockout (KO) mice. Under control conditions at thermoneutral ambient temperature, total sleep time did not differ between TNFα KO and wild-type (WT) mice, but TNFα KO mice had increased rapid-eye-movement sleep (REMS), accompanied by decreased motor activity and body temperature. Exposure to 17 °C induced decreases in total sleep time similarly in both genotypes. Sleep deprivation by gentle handling elicited robust rebound increases in non-rapid-eye movement sleep (NREMS), REMS and electroencephalographic (EEG) slow-wave activity (SWA), accompanied by suppressed motor activity and decreased body temperature; there was no significant difference between the responses of WT and KO mice. Systemic injection of the beta3-adrenergic receptor (β3-AR) agonist CL-316,243 induced increases in NREMS and body temperature. The temperature response, but not the sleep effect, was attenuated in the KO animals. Systemic injection of TNFα induced increased NREMS, reduced REMS and biphasic temperature responses in both genotypes. In the KO mice, the NREMS-promoting effects of exogenously administered TNFα was decreased, while REMS suppression was enhanced, and the first, hypothermic, phase of temperature response was attenuated. Overall, TNFα KO mice did not show any deficiency in sleep regulation which suggests that the role of endogenous TNFα in sleep regulation is less pronounced than previously suggested.

The Sleep-Immune Crosstalk in Health and Disease

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

Unraveling the Evolutionary Determinants of Sleep

Despite decades of intense study, the functions of sleep are still shrouded in mystery. The difficulty in understanding these functions can be at least partly attributed to the varied manifestations of sleep in different animals. Daily sleep duration can range from 4-20 hrs among mammals, and sleep can manifest throughout the brain, or it can alternate over time between cerebral hemispheres, depending on the species. Ecological factors are likely to have shaped these and other sleep behaviors during evolution by altering the properties of conserved arousal circuits in the brain. Nonetheless, core functions of sleep are likely to have arisen early and to have persisted to the present day in diverse organisms. This review will discuss the evolutionary forces that may be responsible for phylogenetic differences in sleep and the potential core functions that sleep fulfills.

Basing Turkey Lighting Programs on Broiler Research: A Good Idea? A Comparison of 18 Daylength Effects on Broiler and Turkey Welfare

Simple Summary

Altering daylength in a poultry management program is a simple tool that can have immense impacts on productivity and bird welfare. It is not uncommon for lighting data derived from broiler research to be extrapolated to turkey production. This review of two studies (one with broilers and the second with turkeys), completed in the same research facility using the same lighting programs, shows evidence that some, but not all responses to graded daylengths are similar between these two species. It defines that daylength choices for turkeys should be based on research conducted with turkeys.

Abstract

Daylength used as a management tool has powerful implications on the welfare of both broilers and turkeys. Near-constant light results in many detrimental impacts, including lack of behavioural rhythms and circadian melatonin rhythms. Both are suggestive that sleep fragmentation could result in birds reared on long photoperiods, which can lead to the same negative health and physiological responses as total sleep deprivation. An indirect comparison of the welfare implications of graded levels of daylength on broilers and turkeys clearly indicate that long daylengths depress welfare by increasing mortality, reducing mobility, increasing ocular pathologies and changing behaviour in both species. Furthermore, long daylengths change melatonin secretion patterns and eliminate behavioural and melatonin circadian rhythms, which were measured in broilers in these works. However, feather pecking in turkeys was reduced when birds were exposed to long daylengths. Exactly how much darkness should be included in a management program to maximize welfare will depend on the species, the age of marketing, and in turkeys, bird gender.

Sleep deprivation-induced multi-organ injury: role of oxidative stress and inflammation

Sleep deprivation affects all aspects of health. Adverse health effects by sleep deviation are still underestimated and undervalued in clinical practice and, to a much greater extent in monitoring human health. We hypothesized that sleep deprivation-induced mild organ injuries; oxidative stress and inflammation might play a crucial role in inducing multi-organ injury. Male C57BL/6J mice (n = 6-7) were sleep-deprived for 0-72 h using a modified multiple platform boxes method. Blood and tissue were collected. Liver, heart, kidney, lung, and pancreatic injuries were evaluated using biochemical and histological analyses. Glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), total billirubin (TBIL), creatine phosphokinase (CPK), creatine phosphokinase-myocardial band (CKMB), lactic dehydrogenase (LDH), creatinine (CRE), and blood urea nitrogen (BUN) were assayed in blood. Malondialdehyde (MDA), nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 levels were measured. Histology revealed mild-to-moderate liver and lung injury in sleep-deprived mice. Sleep-deprived mice had significantly higher GOT, GPT, TBIL, CPK, CKMB, LDH, BUN, and α-amylase (AMYL) levels, which indicated liver, heart, kidney, and pancreatic injuries. Serum IL-1β at 24 h and IL-6 at 72 h were significantly higher in sleep-deprived than in control mice. Hepatic TNF-α and IL-1β were significantly higher, but IL-6 significantly lower in mice that had been sleep-deprived for 72 h. Sleep deprivation-mediated inflammation may be associated with mild to moderate multi-organ damage in mice. The implication of this study indicates sleep deprivation in humans may induce multi-organ injury that negatively affects cardiovascular and gastrointestinal health.

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.

Cell injury and repair resulting from sleep loss and sleep recovery in laboratory rats

STUDY OBJECTIVES

Increased cell injury would provide the type of change in constitution that would underlie sleep disruption as a risk factor for multiple diseases. The current study was undertaken to investigate cell injury and altered cell fate as consequences of sleep deprivation, which were predicted from systemic clues.

DESIGN

Partial (35% sleep reduction) and total sleep deprivation were produced in rats for 10 days, which was tolerated and without overtly deteriorated health. Recovery rats were similarly sleep deprived for 10 days, then allowed undisturbed sleep for 2 days. The plasma, liver, lung, intestine, heart, and spleen were analyzed and compared to control values for damage to DNA, proteins, and lipids; apoptotic cell signaling and death; cell proliferation; and concentrations of glutathione peroxidase and catalase.

MEASUREMENTS AND RESULTS

Oxidative DNA damage in totally sleep deprived rats was 139% of control values, with organ-specific effects in the liver (247%), lung (166%), and small intestine (145%). Overall and organ-specific DNA damage was also increased in partially sleep deprived rats. In the intestinal epithelium, total sleep deprivation resulted in 5.3-fold increases in dying cells and 1.5-fold increases in proliferating cells, compared with control. Recovery sleep restored the balance between DNA damage and repair, and resulted in normal or below-normal metabolic burdens and oxidative damage.

CONCLUSIONS

These findings provide physical evidence that sleep loss causes cell damage, and in a manner expected to predispose to replication errors and metabolic abnormalities; thereby providing linkage between sleep loss and disease risk observed in epidemiological findings. Properties of recovery sleep include biochemical and molecular events that restore balance and decrease cell injury.

Effects of sleep fragmentation on sleep and markers of inflammation in mice

Many people in our society experience curtailment and disruption of sleep due to work responsibilities, care-giving, or life style choice. Delineating the health effect of acute and chronic disruptions in sleep is essential to raising awareness of and creating interventions to manage these prevalent concerns. To provide a platform for studying the health impact and underlying pathophysiologic mechanisms associated with inadequate sleep, we developed and characterized an approach to creating chronic disruption of sleep in laboratory mice. We used this method to evaluate how 3 durations of sleep fragmentation (SF) affect sleep recuperation and blood and lung analyte concentrations in male C57BL/6J mice. Mice housed in environmentally controlled chambers were exposed to automated SF for periods of 6, 12, or 24 h or for 12 h daily during the light (somnolent) phase for 4 sequential days. Sleep time, slow-wave amplitude, or bout lengths were significantly higher when uninterrupted sleep was permitted after each of the 3 SF durations. However, mice did not recover all of the lost slow-wave sleep during the subsequent 12- to 24-h period and maintained a net loss of sleep. Light-phase SF was associated with significant changes in serum and lung levels of some inflammatory substances, but these changes were not consistent or sustained. The data indicate that acute light-phase SF can result in a sustained sleep debt in mice and may disrupt the inflammatory steady-state in serum and lung.

Increased mortality in a colony of zebra finches exposed to continuous light

Over a 1-mo period, increased morbidity and mortality occurred in a flock of zebra finches (Taeniopygia guttata). Complete postmortem examination was performed on 6 of the affected birds, 4 of which subsequently were diagnosed with the avian gastric yeast previously known as megabacteriosis (Macrorhabdus ornithogaster). The remaining 2 birds were diagnosed with a cloacal abscess and with large bowel perforation and peritonitis. All the birds had been prophylactically treated with amphotericin B for megabacteria 2 mo previously. An environmental assessment revealed that the light cycle had been altered, and the birds were being exposed to constant light. With correction of the light cycle, the health of the birds improved dramatically. The remaining birds were treated again with amphotericin B, and baseline mortality returned to normal. The birds in this report show several similarities to previous reports of sleep deprivation syndrome in mammals.

Rats housed on corncob bedding show less slow-wave sleep

Despite the reported advantages of corncob bedding, questions have emerged about how comfortable animals find this type of bedding as a resting surface. In this study, encephalography (EEG) was used to compare the effects of corncob and aspen-chip bedding on rat slow-wave sleep (SWS). According to a facility-wide initiative, rats that were weaned on aspen-chip bedding were switched to corncob bedding in home cages and EEG recording chambers. Spontaneous EEG recordings obtained for 5 wk after the switch to corncob bedding demonstrated that rats spent significantly less time in SWS as compared with levels measured on aspen chips just prior to the bedding switch. SWS remained low even after a 5-wk acclimation period to the corncob bedding. We then acutely switched back to aspen-chip bedding in EEG recording chambers. Acute reinstatement of aspen-chip bedding during EEG recording was associated with an average 22% increase in time spent in SWS, with overall levels of SWS comparable to the levels measured on aspen chips prior to the change to corncob bedding. Aspen-chip bedding subsequently was reinstated in both home cages and EEG recording chambers, and SWS baseline levels were restored. These data raise important concerns about the effects of corncob bedding on rodents used in research.

Chronically inadequate sleep results in abnormal bone formation and abnormal bone marrow in rats

Insufficient sleep over long durations of the lifespan is believed to adversely affect proper development and healthful aging, although how this might become manifested is unknown. In the present study, rats were repeatedly sleep-restricted during 72 days to permit maladaptations to evolve, thereby permitting study. Densitometric and histomorphometric analyses were performed on harvested bone. In sleep-restricted rats, bone lined by osteoid was reduced 45-fold and osteoid thickness was decreased, compared with controls. This corresponded to a decrease in osteoblast number and activity. The percentage of bone lined by osteoclasts did not differ from that of controls. Plasma concentrations of an osteoclast marker (TRACP 5b) were increased in sleep-restricted rats, indicating increased bone resorption. The low amount of new bone formation without a reduction in bone resorption is diagnostic of osteopenia. Bone mineral density was decreased in femurs from sleep-restricted rats compared with controls, indicating osteoporosis. Red marrow in sleep-restricted rats contained only 37% of the fat and more than twice the number of megakaryocytes compared with that of the control rats. These findings in marrow suggest changed plasticity and increased hematopoiesis. Plasma concentrations of insulin-like growth factor-1, a known, major mediator of osteoblast differentiation and the proliferation of progenitor cells, was decreased by 30% in sleep-restricted rats. Taken together, these findings suggest that chronically inadequate sleep affects bone metabolism and bone marrow composition in ways that have implications for development, aging, bone healing and repair, and blood cell differentiation.

Sleep: a health imperative

Chronic sleep deficiency, defined as a state of inadequate or mistimed sleep, is a growing and underappreciated determinant of health status. Sleep deprivation contributes to a number of molecular, immune, and neural changes that play a role in disease development, independent of primary sleep disorders. These changes in biological processes in response to chronic sleep deficiency may serve as etiological factors for the development and exacerbation of cardiovascular and metabolic diseases and, ultimately, a shortened lifespan. Sleep deprivation also results in significant impairments in cognitive and motor performance which increase the risk of motor vehicle crashes and work-related injuries and fatal accidents. The American Academy of Sleep Medicine and the Sleep Research Society have developed this statement to communicate to national health stakeholders the current knowledge which ties sufficient sleep and circadian alignment in adults to health.

Immune outcomes of paradoxical sleep deprivation on cellular distribution in naive and lipopolysaccharide-stimulated mice

BACKGROUND/AIMS

Several lines of evidence indicate that sleep loss imposes significant consequences on the host defense system, including changes in cell number, activity and distribution. However, it is not clear whether cellular alterations after sleep deprivation are caused by redistribution to immune organs or by death of these cells or how the response to a nonspecific immune activator would be affected. Therefore, the aim of this study was to assess the leukocyte distribution after paradoxical sleep deprivation (PSD) in saline- and lipopolysaccharide-treated mice.

METHODS

Adult inbred mice were paradoxical sleep deprived (72 h), whereas the controls were kept in their home cages. After PSD, both groups received an injection of either saline or lipopolysaccharide (LPS; 1 or 5 μg/animal, intraperitoneally), 2 h prior to the collection of blood, spleen, lymph nodes and peritoneal wash. Isolated cells were then designated to differential leukocyte count (blood) and flow cytometry analysis of immune cell subsets (immune sites).

RESULTS

The data revealed that PSD caused a significant reduction of circulating lymphocytes and a general decrease in all cellular subsets of spleen, mainly T and B cells. However, no alteration in response of PSD was found on other immune sites, such as lymph nodes and peritoneum. Of note, immune cell distribution in response to in vivo LPS stimulation remained unchanged after PSD.

CONCLUSIONS

Our study provided original evidence concerning the immune outcomes of PSD, indicating that cellular decrease caused by PSD is not restricted to circulation, but also to immune sites. Taken together, our results could help shed light on the physiological mechanisms of leukocyte trafficking.

Repeated exposure to severely limited sleep results in distinctive and persistent physiological imbalances in rats

Chronic sleep disruption in laboratory rats leads to increased energy expenditure, connective tissue abnormalities, and increased weights of major organs relative to body weight. Here we report on expanded findings and the extent to which abnormalities become long-lasting, potentially permanent changes to health status after apparent recuperation from chronic sleep disruption. Rats were exposed 6 times to long periods of disrupted sleep or control conditions during 10 weeks to produce adaptations and then were permitted nearly 4 months of undisturbed sleep. Measurements were made in tissues from these groups and in preserved tissue from the experimental and control groups of an antecedent study that lacked a lengthy recuperation period. Cycles of sleep restriction resulted in energy deficiency marked by a progressive course of hyperphagia and major (15%) weight loss. Analyses of tissue composition in chronically sleep-restricted rats indicated that protein and lipid amounts in internal organs were largely spared, while adipose tissue depots appeared depleted. This suggests high metabolic demands may have preserved the size of the vital organs relative to expectations of severe energy deficiency alone. Low plasma corticosterone and leptin concentrations appear to reflect low substrate availability and diminished adiposity. After nearly 4 months of recuperation, sleep-restricted rats were consuming 20% more food and 35% more water than did comparison control rats, despite normalized weight, normalized adipocytes, and elevated plasma leptin concentrations. Plasma cholesterol levels in recuperated sleep-restricted rats were diminished relative to those of controls. The chronically increased intake of nutriments and water, along with altered negative feedback regulation and substrate use, indicate that internal processes are modified long after a severe period of prolonged and insufficient sleep has ended.

Evidence for neuroinflammatory and microglial changes in the cerebral response to sleep loss

STUDY OBJECTIVES

Sleep loss has pro-inflammatory effects, but the roles of specific cell populations in mediating these effects have not been delineated. We assessed the modulation of the electroencephalographic and molecular responses to sleep deprivation (S-DEP) by minocycline, a compound that attenuates microglial activation occurring in association with neuroinflammatory events.

DESIGN

Laboratory rodents were subjected to assessment of sleep and wake in baseline and sleep deprived conditions.

PARTICIPANTS

Adult male CD-1 mice (30-35 g) subjected to telemetric electroencephalography.

INTERVENTIONS

Minocycline was administered daily. Mice were subjected to baseline data collection on the first day of minocycline administration and, on subsequent days, 2 S-DEP sessions, 1 and 3 h in duration, followed by recovery sleep. Following EEG studies, mice were euthanized either at the end of a 3 h S-DEP or as time-of day controls for sampling of brain messenger RNAs. Gene expression was measured by real-time polymerase chain reaction.

MEASUREMENTS AND RESULTS

Minocycline-treated mice exhibited a reduction in time spent asleep, relative to saline-treated mice, in the 3-h interval immediately after administration. S-DEP resulted in an increase in EEG slow wave activity relative to baseline in saline-treated mice. This response to S-DEP was abolished in animals subjected to chronic minocycline administration. S-DEP suppressed the expression of the microglial-specific transcript cd11b and the neuroinflammation marker peripheral benzodiazepine receptor, in the brain at the mRNA level. Minocycline attenuated the elevation of c-fos expression by S-DEP. Brain levels of pro-inflammatory cytokine mRNAs interleukin-1β (il-1β), interleukin-6 (il-6), and tumor necrosis factor-α (tnfα) were unaffected by S-DEP, but were elevated in minocycline-treated mice relative to saline-treated mice.

CONCLUSIONS

The anti-neuroinflammatory agent minocycline prevents either the buildup or expression of sleep need in rodents. The molecular mechanism underlying this effect is not known, but it is not mediated by suppression of il-1β, il-6, and tnfα at the transcript level.

Recurrent restriction of sleep and inadequate recuperation induce both adaptive changes and pathological outcomes

Chronic restriction of a basic biological need induces adaptations to help meet requisites for survival. The adaptations to chronic restriction of sleep are unknown. A single episode of 10 days of partial sleep loss in rats previously was shown to be tolerated and to result in increased food intake and loss of body weight as principal signs. The purpose of the present experiment was to investigate the extent to which adaptation to chronic sleep restriction would ameliorate short-term effects and result in a changed internal phenotype. Rats were studied during 10 wk of multiple periods of restricted and unrestricted sleep to allow adaptive changes to develop. Control rats received the same ambulatory requirements only consolidated into periods that lessened interruptions of their sleep. The results indicate a latent period of relatively stable food and water intake without weight gain, followed by a dynamic phase marked by enormous increases in food and water intake and progressive loss of body weight, without malabsorption of calories. Severe consequences ensued, marked especially by changes to the connective tissues, and became fatal for two individuals. The most striking changes to internal organs in sleep-restricted rats included lengthening of the small intestine, decreased size of adipocytes, and increased incidence of multilocular adipocytes. Major organs accounted for an increased proportion of total body mass. These changes to internal tissues appear adaptive in response to high energy production, decomposition of lipids, and increased need to absorb nutrients, but ultimately insufficient to compensate for inadequate sleep.

Sleep viewed as a state of adaptive inactivity

Sleep is often viewed as a vulnerable state that is incompatible with behaviours that nourish and propagate species. This has led to the hypothesis that sleep has survived because it fulfills some universal, but as yet unknown, vital function. I propose that sleep is best understood as a variant of dormant states seen throughout the plant and animal kingdoms and that it is itself highly adaptive because it optimizes the timing and duration of behaviour. Current evidence indicates that ecological variables are the main determinants of sleep duration and intensity across species.