Systemic immune parameters and sleep after ultra-low dose administration of IL-2 in healthy men

Heat of the night: sleep disturbance activates inflammatory mechanisms and induces pain in rheumatoid arthritis

Sleep has a homeostatic role in the regulation of the immune system and serves to constrain activation of inflammatory signalling and expression of cellular inflammation. In patients with rheumatoid arthritis (RA), a misaligned inflammatory profile induces a dysregulation of sleep-wake activity, which leads to excessive inflammation and the induction of increased sensitivity to pain. Given that multiple biological mechanisms contribute to sleep disturbances (such as insomnia), and that the central nervous system communicates with the innate immune system via neuroendocrine and neural effector pathways, potential exists to develop prevention opportunities to mitigate the risk of insomnia in RA. Furthermore, understanding these risk mechanisms might inform additional insomnia treatment strategies directed towards steering and reducing the magnitude of the inflammatory response, which together could influence outcomes of pain and disease activity in RA.

Interleukin-2 Transiently Inhibits Pulsatile Growth Hormone Secretion in Young but not Older Healthy Men

CONTEXT

Interleukin-2 (IL-2), a proinflammatory cytokine, has been used to treat malignancies. Increased cortisol and adrenocorticotropin (ACTH) were noted, but growth hormone (GH) secretion was not investigated in detail.

OBJECTIVE

We quantified GH secretion after a single subcutaneous injection of IL-2 in 17 young and 18 older healthy men in relation to dose, age, and body composition.

METHODS

This was a placebo-controlled, blinded, prospectively randomized, crossover study. At 20:00 hours IL-2 (3 or 6 million units/m2) or saline was injected subcutaneously. Lights were off between 23:00 and 07:00 hours. Blood was sampled at 10-minute intervals for 24 hours. Outcome measures included convolution analysis of GH secretion.

RESULTS

GH profiles were pulsatile under both experimental conditions and lower in older than young volunteers. Since the effect of IL-2 might be time limited, GH analyses were performed on the complete 24-hour series and the 6 hours after IL-2 administration. Total and pulsatile 24-hour GH secretion decreased nonsignificantly. Pulsatile secretion fell over the first 6 hours after IL-2 (P = .03), with visceral fat as a covariate (P = .003), but not age (P = .10). Plots of cumulative 2-hour bins of GH pulse mass showed a distinction by treatment and age groups: A temporary GH decrease of 32% and 28% occurred in the first 2-hour bins after midnight (P = .02 and .04) in young participants, whereas in older individuals no differences were present at any time point.

CONCLUSION

This study demonstrates that IL-2 temporarily diminishes GH secretion in young, but not older, men.

Interleukin-2 drives cortisol secretion in an age-, dose-, and body composition-dependent way

BACKGROUND

Interleukin-2 (IL-2), one of the proinflammatory cytokines, is used in the treatment of certain malignancies. In some studies, transient increases in cortisol and ACTH secretion occurred. Thus, this agent may be used as an experimental probe of adrenal cortisol secretion.

OBJECTIVE

This study quantifies the effects of low and moderate doses of IL-2 on cortisol secretion and assesses the modulation by age, dose and body composition.

SITE

Mayo Clinical Translational Research Unit.

SUBJECTS

Study comprised 35 healthy men, 17 young and 18 older.

METHODS

Randomized prospective double-blind saline-controlled study of IL-2 administration in two doses with concurrent 10-min blood sampling for 24 h.

OUTCOME MEASURES

Deconvolution analysis and approximate entropy of cortisol secretion.

RESULTS

Low-dose IL-2 administration increased nocturnal pulsatile cortisol secretion from 1460 ± 160 to 2120 ± 220 nmol/L/8 h in young subjects and from 1680 ± 105 to 1960 ± 125 nmol/L/8 h (treatment P < 0.0001, but more in young than older, P = 0.02). Comparable results were obtained for total cortisol secretion (P treatment <0.0001, age effect P = 0.005). The higher IL-2 dose caused a large increase in young (P < 0.0001), but not in older (P = 0.90) subjects. This dose also increased approximate entropy from 0.877 ± 0.041 to 1.024 ± 0.049 (P = 0.008), pointing to reduced secretory orderliness. Incremental cortisol (nocturnal) secretion correlated negatively with visceral fat mass (R = -0.41, P = 0.019).

CONCLUSION

In healthy men, IL-2 injection drives pulsatile cortisol secretion in a dose-dependent way in young, but not older, individuals and erodes cortisol secretory orderliness at a higher dose in young subjects. Cortisol responses are diminished with increasing abdominal visceral fat mass.

Sleep and inflammation: partners in sickness and in health

The discovery of reciprocal connections between the central nervous system, sleep and the immune system has shown that sleep enhances immune defences and that afferent signals from immune cells promote sleep. One mechanism by which sleep is proposed to provide a survival advantage is in terms of supporting a neurally integrated immune system that might anticipate injury and infectious threats. However, in modern times, chronic social threats can drive the development of sleep disturbances in humans, which can contribute to the dysregulation of inflammatory and antiviral responses. In this Review, I describe our current understanding of the relationship between sleep dynamics and host defence mechanisms, with a focus on cytokine responses, the neuroendocrine and autonomic pathways that connect sleep with the immune system and the role of inflammatory peptides in the homeostatic regulation of sleep. Furthermore, I discuss the therapeutic potential of harnessing these reciprocal mechanisms of sleep-immune regulation to mitigate the risk of inflammatory and infectious diseases.

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.

Prospective Analyses of Cytokine Mediation of Sleep and Survival in the Context of Advanced Cancer

OBJECTIVE

The aims of this study were to examine the potential association between sleep problems, symptom burden, and survival in patients with advanced cancer.

METHODS

A prospective study of 294 patients with gastrointestinal cancer administered questionnaires assessing sleep, depression, anxiety, stress, pain, fatigue, and health-related quality of life. Serum levels of cytokines including interleukin (IL)-1α, IL-1β, tumor necrosis factor α, IL-10, IL-2, and interferon-γ were measured to assess biological mediation between sleep and survival. Survival was measured as time from diagnosis to death.

RESULTS

Fifty-nine percent of patients reported poor sleep quality, 53% reported poor sleep efficiency, 39% reported sleep latency greater than 30 minutes, and 45% reported sleeping less than 6 hours or greater than 10 hours. We found a significant association between sleep duration and symptom burden. Shorter sleep duration was significantly associated with higher levels of fatigue (r = -0.169, p = .01), pain (r = -0.302, p = .01), anxiety (r = -0.182, p = .01), depression (r = -0.172, p = .003), and lower levels of quality of life (r = 0.240, p = .01). After adjustment for demographic, psychological, and disease-specific factors, short sleep duration was associated with reduced survival (hazard ratio [HR] linear = 0.485, 95% confidence interval = 0.275-0.857) and there was also evidence for a quadratic pattern (HR quadrati = 1.064, 95% confidence interval = 1.015-1.115) suggesting a curvilinear relationship between sleep duration and survival. Interleukin 2 was the only cytokine significantly related to survival (HR = 1.01, p = .003) and sleep duration (β = -30.11, p = .027). When of IL-2 was added to the multivariable model, short and long sleep (β = -0.557, p = .097; β = 0.046, p = .114) were no longer significantly related to survival, suggesting mediation by IL-2.

CONCLUSION

Sleep duration was associated with symptom burden and poorer survival and IL-2 was found to mediate the association between sleep and survival. Screening and treatment of sleep problems in patients diagnosed with cancer are warranted.

Diurnal Variation of Circulating Interleukin-6 in Humans: A Meta-Analysis

The pleiotropic cytokine interleukin-6 (IL-6) has been proposed to contribute to circadian regulation of sleepiness by increasing in the blood at night. Earlier studies have reported diurnal variation of IL-6, but phase estimates are conflicting. We have therefore performed a meta-analysis on the diurnal variation of circulating IL-6. Studies were included if they reported IL-6 in plasma or serum recorded at least twice within 24 hours in the same individual. A systematic search resulted in the inclusion of 43 studies with 56 datasets, for a total of 1100 participants. Individual participant data were available from 4 datasets with a total of 56 participants. Mixed-effects meta-regression modelling confirmed that IL-6 varied across the day, the most conspicuous effect being a trough in the morning. These results stand in contrast to earlier findings of a peak in the evening or night, and suggest that diurnal variation should be taken into account in order to avoid confounding by time of day in studies of IL-6 in plasma or serum.

Proinflammatory Cytokine Infusion Attenuates LH's Feedforward on Testosterone Secretion: Modulation by Age

CONTEXT

In the experimental animal, inflammatory signals quench LH's feedforward drive of testosterone (T) secretion and appear to impair GnRH-LH output. The degree to which such suppressive effects operate in the human is not known.

OBJECTIVE

To test the hypothesis that IL-2 impairs LH's feedforward drive on T and T's feedback inhibition of LH secretion in healthy men.

SETTING

Mayo Center for Translational Science Activities.

PATIENTS OR OTHER PARTICIPANTS

A total of 35 healthy men, 17 young and 18 older.

INTERVENTIONS

Randomized prospective double-blind saline-controlled study of IL-2 infusion in 2 doses with concurrent 10-minute blood sampling for 24 hours.

MAIN OUTCOME MEASURES

Deconvolution analysis of LH and T secretion.

RESULTS

After saline injection, older compared with young men exhibited reduced LH feedforward drive on T secretion (P < .001), and decreased T feedback inhibition of LH secretion (P < .01). After IL-2 injection, LH's feedforward onto T secretion declined markedly especially in young subjects (P < .001). Concomitantly, IL-2 potentiated T's proportional feedback on LH secretion especially in older volunteers.

CONCLUSION

This investigation confirms combined feedforward and feedback deficits in older relative to young men given saline and demonstrates 1) joint mechanisms by which IL-2 enforces biochemical hypogonadism, viz, combined feedforward block and feedback amplification; and 2) unequal absolute inhibition of T and LH secretion by IL-2 in young and older men. These outcomes establish that the male gonadal axis is susceptible to dual-site suppression by a prototypic inflammatory mediator. Thus, we postulate that selected ILs might also enforce male hypogonadism in chronic systemic inflammation.

Why sleep is important for health: a psychoneuroimmunology perspective

Sleep has a critical role in promoting health. Research over the past decade has documented that sleep disturbance has a powerful influence on the risk of infectious disease, the occurrence and progression of several major medical illnesses including cardiovascular disease and cancer, and the incidence of depression. Increasingly, the field has focused on identifying the biological mechanisms underlying these effects. This review highlights the impact of sleep on adaptive and innate immunity, with consideration of the dynamics of sleep disturbance, sleep restriction, and insomnia on (a) antiviral immune responses with consequences for vaccine responses and infectious disease risk and (b) proinflammatory immune responses with implications for cardiovascular disease, cancer, and depression. This review also discusses the neuroendocrine and autonomic neural underpinnings linking sleep disturbance and immunity and the reciprocal links between sleep and inflammatory biology. Finally, interventions are discussed as effective strategies to improve sleep, and potential opportunities are identified to promote sleep health for therapeutic control of chronic infectious, inflammatory, and neuropsychiatric diseases.

Airborne exposure limits for chemical and biological warfare agents: is everything set and clear?

Emergency response strategies (guidelines) for biological, chemical, nuclear, or radiological terrorist events should be based on scientifically established exposure limits for all the agents or materials involved. In the case of a radiological terrorist event, emergency response guidelines (ERG) have been worked out. In the case of a terrorist event with the use of chemical warfare (CW) agents the situation is not that clear, though the new guidelines and clean-up values are being generated based on re-evaluation of toxicological and risk data. For biological warfare (BW) agents, such guidelines do not yet exist. In this paper the current status of airborne exposure limits (AELs) for chemical and biological warfare (CBW) agents are reviewed. Particular emphasis is put on BW agents that lack such data. An efficient, temporary solution to bridge the gap in experimental infectious data and to set provisional AELs for BW agents is suggested. It is based on mathematically generated risks of infection for BW agents grouped by their alleged ID50 values in three categories: with low, intermediate and high ID50 values.

The association between interleukin-6, sleep, and demographic characteristics

We examined the relationship between the pro-inflammatory cytokine IL-6 and sleep architecture in 70 healthy men and women. Blood was drawn in the early morning for assessment of IL-6 followed by nocturnal sleep monitoring with polysomnography. Sleep records were scored for sleep stages using standard criteria. Morning IL-6 levels were positively correlated with REM latency after sleep onset [rho = .31, p = .01], percent (%) stage 1 sleep [rho = .23, p = .053], % wake after sleep onset (WASO) [rho = .29, p<.05]. IL-6 levels were negatively correlated with sleep efficiency [rho = -.36, p<.01] and slow wave sleep (SWS) [rho = -.26, p<.05]. After controlling for demographic variables including race, gender, age, and BMI, multiple hierarchical regression analyses revealed that morning IL-6 levels accounted for a significant portion of the variance of REM latency (p<.01), sleep efficiency (p<.01), and % WASO (p = .01). IL-6 was no longer associated with % stage 1 sleep, SWS, and total sleep time after controlling for the demographic characteristics. These findings suggest that the inflammatory marker IL-6 is associated with sleep quality and that certain individual characteristics such as race, gender, and age modify that relationship. Higher IL-6 levels were associated with lower quality of sleep among healthy asymptomatic men and women.

Diurnal and sleep-wake dependent variations of soluble TNF- and IL-2 receptors in healthy volunteers

There is very little published information on the diurnal variation of cytokines and their receptors, in healthy individuals during normal sleep-wake patterns or during sustained wakefulness. The aim of the current investigation was to characterize concentrations of soluble tumor necrosis factor receptors (sTNF-Rs) and interleukin-2 receptor (sIL-2R) during normal sleep and wakefulness, as well as during a 24 h vigil. Plasma levels of the sTNF-R p55, sTNF-R p75, and sIL-2R did not differ significantly between nocturnal sleep and nocturnal wakefulness. Rhythmic analysis (2-h intervals) revealed significant diurnal variations for both sTNF-R p55 and sTNF-R p75, but not levels of sIL-2R. Diurnal variations of both sTNF-Rs were characterized by a single cosine curve with an average peak near 06:00 h in the morning. This peak occurred well before that of cortisol, and fluctuated inversely with the diurnal rhythm of temperature. These diurnal variations in sTNF-Rs levels are consistent with the hypothesis that the TNF system plays a role in normal diurnal temperature regulation.

Disordered sleep, nocturnal cytokines, and immunity: interactions between alcohol dependence and African-American ethnicity

Sleep disturbance is one of the most prominent complaints of alcohol-dependent patients. In view of recent evidence that the immune system is integrated with other homeostatic processes ultimately regulated by the brain, the influence of sleep on host defense mechanisms and the expression of proinflammatory and T helper cell cytokines deserves attention in alcohol dependence. Although not all immune alterations found in alcohol-dependent persons are related to disordered sleep, it is exceedingly important to know whether sleep influences immunity in alcoholism because of the recognized impact of disordered sleep on infectious disease risk. Conversely, feedback systems are also operating between the brain and the immune system, and abnormalities in the expression of cytokines might contribute to sleep disturbances in alcohol-dependent persons. In this review, we identify the immune alterations found in association with alcohol dependence and discuss the implications of these findings for infectious disease risk, with particular attention to the interaction between African-American ethnicity and alcoholism in contributing to this risk. We provide evidence that sleep disruption occurs in association with alcohol dependence and that African-American alcohol-dependent persons show greater abnormalities in sleep and sleep regulatory processes than shown by Euro-American alcohol-dependent persons. The relations among alcoholism, sleep, and immunity are discussed, with an emphasis on understanding how the cytokine network is altered during sleep in the African-American alcohol-dependent populations. The potential is to use cytokine agonists or antagonists to determine whether physiologic changes in cytokines have a role in the homeostatic regulation of sleep in human beings, which has tremendous implications for the development of novel treatments of alcohol-related sleep disorders.

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.