Effects of low-dose acetylsalicylic acid on the inflammatory response to experimental sleep restriction in healthy humans.

BACKGROUND: Sleep deficiencies, such as manifested in short sleep duration or insomnia symptoms, are known to increase the risk for multiple disease conditions involving immunopathology. Inflammation is hypothesized to be a mechanism through which deficient sleep acts as a risk factor for these conditions. Thus, one potential way to mitigate negative health consequences associated with deficient sleep is to target inflammation. Few interventional sleep studies investigated whether improving sleep affects inflammatory processes, but results suggest that complementary approaches may be necessary to target inflammation associated with sleep deficiencies. We investigated whether targeting inflammation through low-dose acetylsalicylic acid (ASA, i.e., aspirin) is able to blunt the inflammatory response to experimental sleep restriction. METHODS: 46 healthy participants (19F/27M, age range 19-63 years) were studied in a double-blind randomized placebo-controlled crossover trial with three protocols each consisting of a 14-day at-home monitoring phase followed by an 11-day (10-night) in-laboratory stay (sleep restriction/ASA, sleep restriction/placebo, control sleep/placebo). In the sleep restriction/ASA condition, participants took low-dose ASA (81 mg/day) daily in the evening (22:00) during the at-home phase and the subsequent in-laboratory stay. In the sleep restriction/placebo and control sleep/placebo conditions, participants took placebo daily. Each in-laboratory stay started with 2 nights with a sleep opportunity of 8 h/night (23:00-07:00) for adaptation and baseline measurements. Under the two sleep restriction conditions, participants were exposed to 5 nights of sleep restricted to a sleep opportunity of 4 h/night (03:00-07:00) followed by 3 nights of recovery sleep with a sleep opportunity of 8 h/night. Under the control sleep condition, participants had a sleep opportunity of 8 h/night throughout the in-laboratory stay. During each in-laboratory stay, participants had 3 days of intensive monitoring (at baseline, 5th day of sleep restriction/control sleep, and 2nd day of recovery sleep). Variables, including pro-inflammatory immune cell function, C-reactive protein (CRP), and actigraphy-estimated measures of sleep, were analyzed using generalized linear mixed models. RESULTS: Low-dose ASA administration reduced the interleukin (IL)-6 expression in LPS-stimulated monocytes (p<0.05 for condition*day) and reduced serum CRP levels (p<0.01 for condition) after 5 nights of sleep restriction compared to placebo administration in the sleep restriction condition. Low-dose ASA also reduced the amount of cyclooxygenase (COX)-1/COX-2 double positive cells among LPS-stimulated monocytes after 2 nights of recovery sleep following 5 nights of sleep restriction compared to placebo (p<0.05 for condition). Low-dose ASA further decreased wake after sleep onset (WASO) and increased sleep efficiency (SE) during the first 2 nights of recovery sleep (p<0.001 for condition and condition*day). Baseline comparisons revealed no differences between conditions for all of the investigated variables (p>0.05 for condition). CONCLUSION: This study shows that inflammatory responses to sleep restriction can be reduced by preemptive administration of low-dose ASA. This finding may open new therapeutic approaches to prevent or control inflammation and its consequences in those experiencing sleep deficiencies. TRIAL REGISTRATION: ClinicalTrials.gov NCT03377543.

Prolonged experimental sleep disturbance affects the inflammatory resolution pathways in healthy humans.

BACKGROUND: Sleep disturbances, as manifested in insomnia symptoms of difficulties falling asleep or frequent nighttime awakenings, are a strong risk factor for a diverse range of diseases involving immunopathology. Low-grade systemic inflammation has been frequently found associated with sleep disturbances and may mechanistically contribute to increased disease risk. Effects of sleep disturbances on inflammation have been observed to be long lasting and remain after recovery sleep has been obtained, suggesting that sleep disturbances may not only affect inflammatory mediators, but also the so-called specialized pro-resolving mediators (SPMs) that actively resolve inflammation. The goal of this investigation was to test for the first time whether the omega-3 fatty acid-derived D- (RvD) and E-series (RvE) resolvins are impacted by prolonged experimental sleep disturbance (ESD). METHODS: Twenty-four healthy participants (12 F, age 20-42 years) underwent two 19-day in-hospital protocols (ESD/control), separated by > 2 months. The ESD protocol consisted of repeated nights of short and disrupted sleep with intermittent nights of undisturbed sleep, followed by three nights of recovery sleep at the end of the protocol. Under the control sleep condition, participants had an undisturbed sleep opportunity of 8 h/night throughout the protocol. The D- and E-series resolvins were measured in plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: The precursor of the D-series resolvins, 17-HDHA, was downregulated in the ESD compared to the control sleep condition (p <.001 for condition), and this effect remained after the third night of recovery sleep has been obtained. This effect was also observed for the resolvins RvD3, RvD4, and RvD5 (p <.001 for condition), while RvD1 was higher in the ESD compared to the control sleep condition (p <.01 for condition) and RvD2 showed a mixed effect of a decrease during disturbed sleep followed by an increase during recovery sleep in the ESD condition (p <.001 for condition*day interaction). The precursor of E-series resolvins, 18-HEPE, was downregulated in the ESD compared to the control sleep condition (p <.01 for condition) and remained low after recovery sleep has been obtained. This effect of downregulation was also observed for RvE2 (p <.01 for condition), while there was no effect for RvE1 (p >.05 for condition or condition*day interaction). Sex-differential effects were found for two of the D-series resolvins, i.e., RvD2 and RvD4. CONCLUSION: This first investigation on the effects of experimental sleep disturbance on inflammatory resolution processes shows that SPMs, particularly resolvins of the D-series, are profoundly downregulated by sleep disturbances and remain downregulated after recovery sleep has been obtained, suggesting a longer lasting impact of sleep disturbances on these mediators. These findings also suggest that sleep disturbances contribute to the development and progression of a wide range of diseases characterized by immunopathology by interfering with processes that actively resolve inflammation. Pharmacological interventions aimed at promoting inflammatory resolution physiology may help to prevent future disease risk as a common consequence of sleep disturbances. TRIAL REGISTRATION: ClinicalTrials.gov NCT02484742.

Alterations of pain pathways by experimental sleep disturbances in humans: central pain-inhibitory, cyclooxygenase, and endocannabinoid pathways.

STUDY OBJECTIVES: There is strong evidence that sleep disturbances are an independent risk factor for the development of chronic pain conditions. The mechanisms underlying this association, however, are still not well understood. We examined the effect of experimental sleep disturbances (ESDs) on three pathways involved in pain initiation/resolution: (1) the central pain-inhibitory pathway, (2) the cyclooxygenase (COX) pathway, and (3) the endocannabinoid (eCB) pathway. METHODS: Twenty-four healthy participants (50% females) underwent two 19-day long in-laboratory protocols in randomized order: (1) an ESD protocol consisting of repeated nights of short and disrupted sleep with intermittent recovery sleep; and (2) a sleep control protocol consisting of nights with an 8-hour sleep opportunity. Pain inhibition (conditioned pain modulation, habituation to repeated pain), COX-2 expression at monocyte level (lipopolysaccharide [LPS]-stimulated and spontaneous), and eCBs (arachidonoylethanolamine, 2-arachidonoylglycerol, docosahexaenoylethanolamide [DHEA], eicosapentaenoylethanolamide, docosatetraenoylethanolamide) were measured every other day throughout the protocol. RESULTS: The central pain-inhibitory pathway was compromised by sleep disturbances in females, but not in males (p < 0.05 condition × sex effect). The COX-2 pathway (LPS-stimulated) was activated by sleep disturbances (p < 0.05 condition effect), and this effect was exclusively driven by males (p < 0.05 condition × sex effect). With respect to the eCB pathway, DHEA was higher (p < 0.05 condition effect) in the sleep disturbance compared to the control condition, without sex-differential effects on any eCBs. CONCLUSIONS: These findings suggest that central pain-inhibitory and COX mechanisms through which sleep disturbances may contribute to chronic pain risk are sex specific, implicating the need for sex-differential therapeutic targets to effectively reduce chronic pain associated with sleep disturbances in both sexes. CLINICAL TRIALS REGISTRATION: NCT02484742: Pain Sensitization and Habituation in a Model of Experimentally-induced Insomnia Symptoms. https://clinicaltrials.gov/ct2/show/NCT02484742.

Differential effects of an experimental model of prolonged sleep disturbance on inflammation in healthy females and males.

Sleep disturbances, including disrupted sleep and short sleep duration, are highly prevalent and are prospectively associated with an increased risk for various widespread diseases, including cardiometabolic, neurodegenerative, chronic pain, and autoimmune diseases. Systemic inflammation, which has been observed in populations experiencing sleep disturbances, may mechanistically link disturbed sleep with increased disease risks. To determine whether sleep disturbances are causally responsible for the inflammatory changes reported in population-based studies, we developed a 19-day in-hospital experimental model of prolonged sleep disturbance inducing disrupted and shortened sleep. The model included delayed sleep onset, frequent nighttime awakenings, and advanced sleep offset, interspersed with intermittent nights of undisturbed sleep. This pattern aimed at providing an ecologically highly valid experimental model of the typical sleep disturbances often reported in the general and patient populations. Unexpectedly, the experimental sleep disturbance model reduced several of the assessed proinflammatory markers, namely interleukin(IL)-6 production by monocytes and plasma levels of IL-6 and C-reactive protein (CRP), presumably due to intermittent increases in the counterinflammatory hormone cortisol. Striking sex differences were observed with females presenting a reduction in proinflammatory markers and males showing a predominantly proinflammatory response and reductions of cortisol levels. Our findings indicate that sleep disturbances causally dysregulate inflammatory pathways, with opposing effects in females and males. These results have the potential to advance our mechanistic understanding of the pronounced sexual dimorphism in the many diseases for which sleep disturbances are a risk factor.

Photoperiodic Effects on Diurnal Rhythms in Cell Numbers of Peripheral Leukocytes in Domestic Pigs.

The photoperiod is known to modulate immune cell number and function and is regarded essential for seasonal disease susceptibility. In addition, diurnal variations in the immune system are regarded important for immune competence. Whereas few studies investigated the influence of season, none investigated the specific effect of the photoperiod on these diurnal immune rhythms until now. Therefore, the present study compared diurnal rhythms in cell numbers of peripheral leukocyte types in domestic pigs held either under long day conditions (LD) or short day conditions (SD). Cosinor analyses of cell numbers of various peripheral leukocyte subtypes investigated over periods of 50 h revealed distinct photoperiodic differences in diurnal immune rhythms. Relative amplitudes of cell numbers of total leukocytes, NK cells, T cells, and monocytes in blood were higher under SD than LD. In addition, cell counts of total leukocytes, NK cells, T cells including various T cell subtypes, and eosinophils peaked earlier relative to the time of lights-on under SD than LD. In contrast, diurnal rhythms of neutrophil counts did not show photoperiodic differences. Mesor values did not differ in any leukocyte type. Generalized linear mixed model analyses revealed associations of leukocyte counts with plasma cortisol concentration and activity behavior in most investigated cell types. Moreover, the present study demonstrated photoperiodic effects on diurnal rhythms in plasma cortisol concentrations and activity behavior, which is in agreement with human and primate studies. The results of the present study imply stronger rhythmicity in leukocyte counts in general under SD. Common intrinsic mechanisms seem to regulate photoperiodic effects on diurnal rhythms in leukocyte counts, except for neutrophils, in domestic pigs. Our results reveal considerable insights into the regulation of immune rhythms in diurnally active species.

Data characterizing diurnal rhythms in the number of peripheral CD8α- and CD8α+ γδ T cells in domestic pigs.

This data article is related to the original research article "Diurnal rhythms in peripheral blood immune cell numbers of domestic pigs" of Engert et al. [1] and describes diurnal rhythms in the number of CD8α- and CD8α+ γδ T cells in peripheral blood of domestic pigs. Blood samples were taken from 18 animals over periods of up to 50 h and immune cell subtypes were determined by flow cytometry. Diurnal rhythmicity of cell numbers of γδ T cell subtypes was analyzed with cosinor analysis and different properties of rhythmicity (mesor, amplitude, and peak time) were calculated. In addition, associations between cell numbers of the investigated cell types in porcine blood with plasma cortisol concentration, hematocrit, and experimental conditions were identified with linear mixed model analysis.

Diurnal rhythms in peripheral blood immune cell numbers of domestic pigs.

Diurnal rhythms within the immune system are considered important for immune competence. Until now, they were mostly studied in humans and rodents. However, as the domestic pig is regarded as suitable animal model and due to its importance in agriculture, this study aimed to characterize diurnal rhythmicity in porcine circulating leukocyte numbers. Eighteen pigs were studied over periods of up to 50 h. Cosinor analyses revealed diurnal rhythms in cell numbers of most investigated immune cell populations in blood. Whereas T cell, dendritic cell, and eosinophil counts peaked during nighttime, NK cell and neutrophil counts peaked during daytime. Relative amplitudes of cell numbers in blood differed in T helper cell subtypes with distinctive differentiation states. Mixed model analyses revealed that plasma cortisol concentration was negatively associated with cell numbers of most leukocyte types, except for NK cells and neutrophils. The observed rhythms mainly resemble those found in humans and rodents.