Somnogenic, pyrogenic, and anorectic activities of tumor necrosis factor-alpha and TNF-alpha fragments

Impact of the addition of dexmedetomidine to patient-controlled intravenous analgesia on postoperative pain-sleep interaction cycle and delirium: A systematic review and meta-analysis of randomized controlled trials

Background

The reciprocal nexus between sleep and pain is well-documented, with the deleterious impact of operative trauma potentially playing a pivotal role in the dysregulation of this interplay, which could significantly contribute to the manifestation of postoperative delirium (POD). Studies have investigated the effect of adding dexmedetomidine (DEX) to patient-controlled intravenous analgesia (PCIA) pumps on postoperative pain-sleep interaction cycle and POD, but conclusions remained uncertain. The objective of this investigation is to perform a meta-analysis that thoroughly assesses the impact of integrating DEX into PCIA, focusing on analgesic effectiveness, sleep quality, and the incidence of delirium in postoperative patients.

Methods

PubMed, Embase, Cochrane Library, SinoMed, and Wanfang Data Knowledge Service Platform were searched, for publications in any language, from database inception to September 2023. Our analysis encompassed randomized controlled trials (RCTs) that examine the therapeutic efficacy and risk profile of adding DEX to the PCIA on the postoperative pain-sleep interaction cycle, by focusing on changes in postoperative analgesia (Visual analog scale (VAS) score), sleep efficiency, sleep structure, subjective sleep score (Assen insomnia scale and numerical rating scale) and adverse event rate.

Results

34 RCTs (4324 patients) were analyzed. This study shows DEX improved analgesia and reduced VAS scores at 6, 12, and 24 h after surgery. Sleep efficiency was enhanced on the 1st and 2nd postoperative night. DEX improved sleep structure at the 1st postoperative night by reducing non-rapid eye movement stage 1 (N1) sleep and increasing non-rapid eye movement stage 2 (N2) and non-rapid eye movement stage 3 (N3) sleep. At the 2nd night, DEX reduced N1 sleep and increased N2 sleep, but not N3 sleep. Data from AIS and NRS showed improvement in subjective sleep scores on the 1st postoperative night and 2nd night. Additionally, DEX decreased the occurrence of POD on the 24 h and first-three days.

Conclusion

This study shows that the typical DEX doses added to PCIA with sufentanil were 2-5 μg/kg or approximately 200-250 μg, and the addition of DEX to PCIA can improve pain-sleep interaction cycle from multiple perspectives, and further decrease the occurrence of POD.

Connecting the dots: An updated review of the role of autoimmunity in narcolepsy and emerging immunotherapeutic approaches

BACKGROUND

Narcolepsy type 1 (NT1) is a chronic disorder characterized by pathological daytime sleepiness and cataplexy due to the disappearance of orexin immunoreactive neurons in the hypothalamus. Genetic and environmental factors point towards a potential role for inflammation and autoimmunity in the pathogenesis of the disease. This study aims to comprehensively review the latest evidence on the autoinflammatory mechanisms and immunomodulatory treatments aimed at suspected autoimmune pathways in NT1.

METHODS

Recent relevant literature in the field of narcolepsy, its autoimmune hypothesis, and purposed immunomodulatory treatments were reviewed.

RESULTS

Narcolepsy is strongly linked to specific HLA alleles and T-cell receptor polymorphisms. Furthermore, animal studies and autopsies have found infiltration of T cells in the hypothalamus, supporting T cell-mediated immunity. However, the role of autoantibodies has yet to be definitively established. Increased risk of NT1 after H1N1 infection and vaccination supports the autoimmune hypothesis, and the potential role of coronavirus disease 2019 and vaccination in triggering autoimmune neurodegeneration is a recent finding. Alterations in cytokine levels, gut microbiota, and microglial activation indicate a potential role for inflammation in the disease's development. Reports of using immunotherapies in NT1 patients are limited and inconsistent. Early treatment with IVIg, corticosteroids, plasmapheresis, and monoclonal antibodies has seldomly shown some potential benefits in some studies.

CONCLUSION

The current body of literature supports that narcolepsy is an autoimmune disorder most likely caused by T-cell involvement. However, the potential for immunomodulatory treatments to reverse the autoinflammatory process remains understudied. Further clinical controlled trials may provide valuable insights into this area.

Gender Differences in the Context of Obstructive Sleep Apnea and Metabolic Diseases

The relationship between obstructive sleep apnea (OSA) and endocrine and metabolic disease is unequivocal. OSA, which is characterized by intermittent hypoxia and sleep fragmentation, leads to and exacerbates obesity, metabolic syndrome, and type 2 diabetes (T2D) as well as endocrine disturbances, such as hypothyroidism and Cushing syndrome, among others. However, this relationship is bidirectional with endocrine and metabolic diseases being considered major risk factors for the development of OSA. For example, polycystic ovary syndrome (PCOS), one of the most common endocrine disorders in women of reproductive age, is significantly associated with OSA in adult patients. Several factors have been postulated to contribute to or be critical in the genesis of dysmetabolic states in OSA including the increase in sympathetic activation, the deregulation of the hypothalamus-pituitary axis, the generation of reactive oxygen species (ROS), insulin resistance, alteration in adipokines levels, and inflammation of the adipose tissue. However, probably the alterations in the hypothalamus-pituitary axis and the altered secretion of hormones from the peripheral endocrine glands could play a major role in the gender differences in the link between OSA-dysmetabolism. In fact, normal sleep is also different between men and women due to the physiologic differences between genders, with sex hormones such as progesterone, androgens, and estrogens, being also connected with breathing pathologies. Moreover, it is very well known that OSA is more prevalent among men than women, however the prevalence in women increases after menopause. At the same time, the step-rise in obesity and its comorbidities goes along with mounting evidence of clinically important sex and gender differences. Metabolic and cardiovascular diseases, seen as a men's illness for decades, presently are more common in women than in men and obesity has a higher association with insulin-resistance-related risk factors in women than in men. In this way, in the present manuscript, we will review the major findings on the overall mechanisms that connect OSA and dysmetabolism giving special attention to the specific regulation of this relationship in each gender. We will also detail the gender-specific effects of hormone replacement therapies on metabolic control and sleep apnea.

A wake-like state in vitro induced by transmembrane TNF/soluble TNF receptor reverse signaling

Tumor necrosis factor alpha (TNF) has sleep regulatory and brain development roles. TNF promotes sleep in vivo and in vitro while TNF inhibition diminishes sleep. Transmembrane (tm) TNF and the tmTNF receptors (Rs), are cleaved by tumor necrosis factor alpha convertase to produce soluble (s) TNF and sTNFRs. Reverse signaling occurs in cells expressing tmTNF upon sTNFR binding. sTNFR administration in vivo inhibits sleep, thus we hypothesized that a wake-like state in vitro would be induced by sTNFR-tmTNF reverse signaling. Somatosensory cortical neuron/glia co-cultures derived from male and female mice lacking both TNFRs (TNFRKO), or lacking TNF (TNFKO) and wildtype (WT) mice were plated onto six-well multi-electrode arrays. Daily one-hour electrophysiological recordings were taken on culture days 4 through 14. sTNFR1 (0.0, 0.3, 3, 30, 60, and 120 ng/µL) was administered on day 14. A final one-hour recording was taken on day 15. Four measures were characterized that are also used to define sleep in vivo: action potentials (APs), burstiness index (BI), synchronization of electrical activity (SYN), and slow wave power (SWP; 0.25-3.75 Hz). Development rates of these emergent electrophysiological properties increased in cells from mice lacking TNF or both TNFRs compared to cells from WT mice. Decreased SWP, after the three lowest doses (0.3, 3 and 30 ng/µL) of the sTNFR1, indicate a wake-like state in cells from TNFRKO mice. A wake-like state was also induced after 3 ng/µl sTNFR1 treatment in cells from TNFKO mice, which express the TNFR1 ligand, lymphotoxin alpha. Cells from WT mice showed no treatment effects. Results are consistent with prior studies demonstrating involvement of TNF in brain development, TNF reverse signaling, and sleep regulation in vivo. Further, the current demonstration of sTNFR1 induction of a wake-like state in vitro is consistent with the idea that small neuronal/glial circuits manifest sleep- and wake-like states analogous to those occurring in vivo. Finally, that sTNF forward signaling enhances sleep while sTNFR1 reverse signaling enhances a wake-like state is consistent with other sTNF/tmTNF/sTNFR1 brain actions having opposing activities.

Lipoteichoic acid, a cell wall component of Gram-positive bacteria, induces sleep and fever and suppresses feeding

Fragments of the bacterial cell wall are bioactive microbial molecules that have profound effects on the function of the brain. Some of the cell wall constituents are common to both Gram-positive and Gram-negative bacteria, e.g., peptidoglycans, while other cell wall components are specific to either Gram-positive or Gram-negative microbes. Lipopolysaccharide (LPS), also called endotoxin, is found exclusively in Gram-negative bacteria, while lipoteichoic acid (LTA) is specific to Gram-positive bacteria. The effects of peptidoglycans, their fragments, and LPS are well characterized, they induce sleep, fever and anorexia. In the present study, we investigated the sleep, body temperature and food intake modulating effects of LTA. We found that intraperitoneal injection of 100 and 250 μg LTA from B. subtilis and S. aureus increases non-rapid-eye movement sleep (NREMS) in mice. The effects were dose-dependent, and the changes were accompanied by decreased motor activity and feeding as well as febrile responses. Intraperitoneal injection of 10 μg LTA induced monophasic increases in body temperature, while 100 and 250 μg LTA from B. subtilis induced initial hypothermia followed by fever. Treatment with 250 μg LTA from S. aureus elicited monophasic hypothermia. Administration of 300 μg/kg LTA from S. aureus directly into the portal vein elicited similar sleep responses in rats but did not affect body temperature. The sleep-modulating effects of LTA were similar to that of LPS in mice, although LTA appears to be less potent. These findings suggest that the role of LTA in signaling by Gram-positive bacteria in the host body is analogous to the role of LPS/endotoxin in signaling by Gram-negative microbes. LTA may play a role in the development of sickness response in clinically manifest Gram-positive bacterial infections and may contribute to sleep signaling by the commensal intestinal microbiota.

Tumor Necrosis Factor α and Interleukin-1β Acutely Inhibit AgRP Neurons in the Arcuate Nucleus of the Hypothalamus

Obesity-associated low-grade inflammation favors weight gain, whereas systemic infection frequently leads to anorexia. Thus, inflammatory signals can either induce positive or negative energy balance. In this study, we used whole-cell patch-clamp to investigate the acute effects of three important proinflammatory cytokines, tumor necrosis factor α (TNF-α), interleukin-6, and interleukin-1β (IL-1β) on the membrane excitability of agouti-related peptide (AgRP)- or proopiomelanocortin (POMC)-producing neurons. We found that both TNF-α and IL-1β acutely inhibited the activity of 35-42% of AgRP-producing neurons, whereas very few POMC neurons were depolarized by TNF-α. Interleukin-6 induced no acute changes in the activity of AgRP or POMC neurons. Our findings indicate that the effect of TNF-α and IL-1β, especially on the activity of AgRP-producing neurons, may contribute to inflammation-induced anorexia observed during acute inflammatory conditions.

Poor sleep is associated with higher blood pressure and uterine artery pulsatility index in pregnancy: a prospective cohort study

Objective

To elucidate the association between sleep disturbances and blood pressure as well as uterine artery Doppler during pregnancy in women with no pre‐existing hypertension.

Design

Prospective cohort study.

Setting

Outpatient specialist clinics at KK Women’s and Children’s Hospital, Singapore.

Population

Women with viable singleton pregnancies confirmed by ultrasonography at less than 14 weeks of amenorrhoea at first visit.

Methods

In all, 926 subjects were recruited for this study in the outpatient specialist clinics at KK Women’s and Children’s Hospital, Singapore, between 1 September 2010 and 31 August 2014. They were followed up throughout pregnancy with sleep quality, blood pressure and uterine artery Doppler assessed at each visit.

Main outcome measures

Sleep quality, blood pressure and uterine artery Doppler.

Results

Sleep progressively worsened as pregnancy advanced. Shorter sleep duration and poorer sleep efficiency were associated with higher blood pressure, especially in the first trimester. Mixed model analysis demonstrated an overall positive association between sleep quality represented by Pittsburgh Sleep Quality Index (PSQI) score and diastolic blood pressure (DBP) (P < 0.001) and mean arterial pressure (MAP) (P = 0.005) during pregnancy after considering all trimesters. Sleep duration was found to be negatively associated with both systolic blood pressure (SBP) (P = 0.029) and DBP (P = 0.002), whereas sleep efficiency was negatively correlated with DBP (P = 0.002) only. Overall poor sleep during pregnancy was also found to be associated with a higher uterine artery pulsatility index.

Conclusion

Our prospective study demonstrated that poor sleep quality is significantly associated with higher blood pressure and uterine artery pulsatility index during pregnancy.

Tweetable abstract

Poor sleep quality is significantly associated with higher blood pressure and higher uterine artery pulsatility index during pregnancy.

Poor sleep quality is significantly associated with higher blood pressure and higher uterine artery pulsatility index during pregnancy.

Nicotinic acid promotes sleep through prostaglandin synthesis in mice

Nicotinic acid has been used for decades for its antiatherogenic properties in humans. Its actions on lipid metabolism intersect with multiple sleep regulatory mechanisms, but its effects on sleep have never been documented. For the first time, we investigated the effects of acute systemic administration of nicotinic acid on sleep in mice. Intraperitoneal and oral gavage administration of nicotinic acid elicited robust increases in non-rapid-eye movement sleep (NREMS) and decreases in body temperature, energy expenditure and food intake. Preventing hypothermia did not affect its sleep-inducing actions suggesting that altered sleep is not secondary to decreased body temperature. Systemic administration of nicotinamide, a conversion product of nicotinic acid, did not affect sleep amounts and body temperature, indicating that it is not nicotinamide that underlies these actions. Systemic administration of monomethyl fumarate, another agonist of the nicotinic acid receptor GPR109A, fully recapitulated the somnogenic and thermoregulatory effects of nicotinic acid suggesting that they are mediated by the GPR109A receptor. The cyclooxygenase inhibitor indomethacin completely abolished the effects of nicotinic acid indicating that prostaglandins play a key role in mediating the sleep and thermoregulatory responses of nicotinic acid.

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.

Activation of Murine Immune Cells upon Co-culture with Plasma-treated B16F10 Melanoma Cells

Recent advances in melanoma therapy increased median survival in patients. However, death rates are still high, motivating the need of novel avenues in melanoma treatment. Cold physical plasma expels a cocktail of reactive species that have been suggested for cancer treatment. High species concentrations can be used to exploit apoptotic redox signaling pathways in tumor cells. Moreover, an immune-stimulatory role of plasma treatment, as well as plasma-killed tumor cells, was recently proposed, but studies using primary immune cells are scarce. To this end, we investigated the role of plasma-treated murine B16F10 melanoma cells in modulating murine immune cells’ activation and marker profile. Melanoma cells exposed to plasma showed reduced metabolic and migratory activity, and an increased release of danger signals (ATP, CXCL1). This led to an altered cytokine profile with interleukin-1β (IL-1β) and CCL4 being significantly increased in plasma-treated mono- and co-cultures with immune cells. In T cells, plasma-treated melanoma cells induced extracellular signal-regulated Kinase (ERK) phosphorylation and increased CD28 expression, suggesting their activation. In monocytes, CD115 expression was elevated as a marker for activation. In summary, here we provide proof of concept that plasma-killed tumor cells are recognized immunologically, and that plasma exerts stimulating effects on immune cells alone.

Neuroendocrine Control of Sleep

Sleep is a phenomenon in animal behavior as enigmatic as it is ubiquitous, and one deeply tied to endocrine function. Though there are still many unanswered questions about the neurochemical basis of sleep and its functions, extensive interactions have been identified between sleep and the endocrine system, in both the endocrine system's effect on sleep and sleep's effect on the endocrine system. Unfortunately, until recent years, much research on sleep behavior largely disregarded its connections with the endocrine system. Use of both clinical studies and rodent models to investigate interactions between neuroendocrine function, including biological sex, and sleep therefore presents a promising area of further exploration. Further investigation of the neurobiological and neuroendocrine basis of sleep could have wide impact on a number of clinical and basic science fields. In this review, we summarize the state of basic sleep biology and its connections to the field of neuroendocrine biology, as well as suggest key future directions for the neuroendocrine regulation of sleep that may significantly impact new therapies for sleep disorders in women and men.

Postoperative sleep disorders and their potential impacts on surgical outcomes

Postoperative sleep disturbance is a common occurrence with significant adverse effects on patients including delayed recovery, impairment of cognitive function, pain sensitivity and cardiovascular events. The development of postoperative sleep disturbance is multifactorial and involves the surgical inflammatory response, the severity of surgical trauma, pain, anxiety, the use of anesthetics and environmental factors such as nocturnal noise and light levels. Many of these factors can be managed perioperatively to minimize the deleterious impact on sleep. Pharmacological and non-pharmacological treatment strategies for postoperative sleep disturbance include dexmedetomidine, zolpidem, melatonin, enhanced recovery after surgery (ERAS) protocol and controlling of environmental noise and light levels. It is likely that a combination of pharmacological and non-pharmacological therapies will have the greatest impact; however, further research is required before their use can be routinely recommended.

A phenotype of increased sleepiness in a mouse model of pulmonary hypertension and right ventricular hypertrophy

The relationship between cardiovascular disease and abnormalities in sleep architecture is complex and bi-directional. Sleep disordered breathing (SDB) often confounds human studies examining sleep in the setting of heart failure, and the independent impact of isolated right or left heart failure on sleep is difficult to assess. We utilized an animal model of right heart failure using pulmonary artery banding (PAB) in mice to examine the causal effect of right heart failure on sleep architecture. Four weeks after PAB or sham (control) surgery, sleep was measured by polysomnography for 48 hours and right ventricular (RV) hypertrophy confirmed prior to sacrifice. PAB resulted in right ventricular hypertrophy based on a 30% increase in the Fulton Index (p < 0.01). After PAB, mice spent significantly more time in NREM sleep compared to the control group over a 24 hour period (53.5 ± 1.5% vs. 46.6 ± 1.4%; p < 0.01) and exhibited an inability to both cycle into REM sleep and decrease delta density across the light/sleep period. Our results support a phenotype of impaired sleep cycling and increased ‘sleepiness’ in a mouse model of RV dysfunction.

Mice Lacking Alternatively Activated (M2) Macrophages Show Impairments in Restorative Sleep after Sleep Loss and in Cold Environment

The relationship between sleep, metabolism and immune functions has been described, but the cellular components of the interaction are incompletely identified. We previously reported that systemic macrophage depletion results in sleep impairment after sleep loss and in cold environment. These findings point to the role of macrophage-derived signals in maintaining normal sleep. Macrophages exist either in resting form, classically activated, pro-inflammatory (M1) or alternatively activated, anti-inflammatory (M2) phenotypes. In the present study we determined the contribution of M2 macrophages to sleep signaling by using IL-4 receptor α-chain-deficient [IL-4Rα knockout (KO)] mice, which are unable to produce M2 macrophages. Sleep deprivation induced robust increases in non-rapid-eye-movement sleep (NREMS) and slow-wave activity in wild-type (WT) animals. NREMS rebound after sleep deprivation was ~50% less in IL-4Rα KO mice. Cold exposure induced reductions in rapid-eye-movement sleep (REMS) and NREMS in both WT and KO mice. These differences were augmented in IL-4Rα KO mice, which lost ~100% more NREMS and ~25% more REMS compared to WTs. Our finding that M2 macrophage-deficient mice have the same sleep phenotype as mice with global macrophage depletion reconfirms the significance of macrophages in sleep regulation and suggests that the main contributors are the alternatively activated M2 cells.

Manipulating the immune system for pigs to optimise performance

Disease and enhanced microbial load are considered to be major factors limiting the performance and overall efficiency of feed use by pigs in Australian piggeries. It is recognised that pigs exposed to conventional housing systems with high microbial loads grow 10–20% more slowly than do gnotobiotic pigs or pigs kept in ‘clean’ environments. Consequently, a proportion of pigs in any production cycle are continuously being challenged by their immediate environment, which can cause an immune response to be mounted. Such a process is physiologically expensive in terms of energy and protein (comprised of amino acids), with, for example, the enhanced rate of protein turnover associated with the production of immune cells, antibodies and acute-phase proteins increasing energy expenditure by 10–15% of maintenance needs and protein requirements by 7–10%. The requirements for lysine, tryptophan, sulfur-containing amino acids and threonine can be increased by a further 10%. The over-stimulation of the immune response with excess production of pro-inflammatory cytokines causes excessive production primarily of the prostaglandin E2 (PGE2), which contributes to anorexia, fever and increased proteolysis, and a concomitant reduction in pig performance. Prostaglandin E2 is produced from dietary and cell-membrane phospholipids via secretory phospholipase A2 (sPLA2) to produce arachidonic acid, which is catalysed by the COX-2 enzyme. Negating the negative effects of PGE2 appears not to adversely affect the ability of the immune system to combat pathogens, but improves pig performance. There are negative outcomes for pig health and productivity through both under- and over-stimulation of the immune response. This review briefly outlines the impact of immune stimulation on pigs and discusses strategies to optimise the immune response for pig health and performance.

Dissociation of Objective and Subjective Daytime Sleepiness and Biomarkers of Systemic Inflammation in Sleep-Disordered Breathing and Systolic Heart Failure

STUDY OBJECTIVES

Subjective versus objective sleepiness in heart failure (HF) remains understudied; therefore, we sought to examine the association of these measures and interrelationships with biochemical markers.

METHODS

Participants with stable systolic HF recruited from a clinic-based program underwent attended polysomnography, Multiple Sleep Latency Testing, questionnaire data collection including Epworth Sleepiness Scale (ESS), and morning phlebotomy for biochemical markers. Linear regression was used to assess the association of mean sleep latency (MSL) and ESS (and other reported outcomes) with adjustment of age or body mass index or left ventricular ejection fraction (LVEF) (beta coefficients, 95% confidence interval) and also with biochemical markers (beta coefficients, 95% confidence interval).

RESULTS

The final analytic sample comprised 26 participants: 52 ± 14 years with apnea-hypopnea index (AHI): 34 ± 27, LVEF: 34 ± 12%, MSL: 7 ± 5 minutes and ESS: 7 (5, 10). There was no significant association of MSL and ESS (-0.36, -0.81 to 0.09, P = .11), AHI, or other questionnaire-based outcomes in adjusted analyses. Although statistically significant associations of ESS and biomarkers were not observed, there were associations of MSL and cortisol (μg/dL) [-0.05: -0.08, -0.01, P = .012] and interleukin-6 (pg/mL) [-0.11: -0.18, -0.04, P = .006], which persisted in adjusted models.

CONCLUSIONS

In systolic HF, although overall objective sleepiness was observed, this was not associated with subjective sleepiness (ie, a discordance was identified). Differential upregulation of systemic inflammation in objective sleepiness was observed, findings not observed with subjective sleepiness. These findings suggest that underlying mechanistic pathways of inflammation may provide the explanation for dissonance of objective and subjective sleepiness symptoms in HF, thus potentially informing targeted diagnostic and therapeutic approaches.

COMMENTARY

A commentary on this article appears in this issue on page 1369.

The role of the brown adipose tissue in β3-adrenergic receptor activation-induced sleep, metabolic and feeding responses

Brown adipose tissue (BAT) is regulated by the sympathetic nervous system via β3-adrenergic receptors (β3-AR). Here we tested the hypothesis that pharmacological stimulation of β3-ARs leads to increased sleep in mice and if this change is BAT dependent. In wild-type (WT) animals, administration of CL-316,243, a selective β3-AR agonist, induced significant increases in non-rapid-eye movement sleep (NREMS) lasting for 4–10 h. Simultaneously, electroencephalographic slow-wave activity (SWA) was significantly decreased and body temperature was increased with a delay of 5–6 h. In uncoupling protein 1 (UCP-1) knockout mice, the middle and highest doses of the β3-AR agonist increased sleep and suppressed SWA, however, these effects were significantly attenuated and shorter-lasting as compared to WT animals. To determine if somnogenic signals arising from BAT in response to β3-AR stimulation are mediated by the sensory afferents of BAT, we tested the effects of CL-316,243 in mice with the chemical deafferentation of the intra-scapular BAT pads. Sleep responses to CL-316,243 were attenuated by ~50% in intra-BAT capsaicin-treated mice. Present findings indicate that the activation of BAT via β3-AR leads to increased sleep in mice and that this effect is dependent on the presence of UCP-1 protein and sleep responses require the intact sensory innervation of BAT.

Metabolic signals in sleep regulation: recent insights

Sleep and energy balance are essential for health. The two processes act in concert to regulate central and peripheral homeostasis. During sleep, energy is conserved due to suspended activity, movement, and sensory responses, and is redirected to restore and replenish proteins and their assemblies into cellular structures. During wakefulness, various energy-demanding activities lead to hunger. Thus, hunger promotes arousal, and subsequent feeding, followed by satiety that promotes sleep via changes in neuroendocrine or neuropeptide signals. These signals overlap with circuits of sleep-wakefulness, feeding, and energy expenditure. Here, we will briefly review the literature that describes the interplay between the circadian system, sleep-wake, and feeding-fasting cycles that are needed to maintain energy balance and a healthy metabolic profile. In doing so, we describe the neuroendocrine, hormonal/peptide signals that integrate sleep and feeding behavior with energy metabolism.

Association between sleeping hours and cardiometabolic risk factors for metabolic syndrome in a Saudi Arabian population

OBJECTIVES

Epidemiological and molecular studies have shown that sleep duration is associated with metabolic syndrome (MtS), a disease that is on the rise in the Kingdom of Saudi Arabia. We aim to investigate the association between sleep duration and selected cardiometabolic risk factors of MtS in a Saudi Arabian population.

SETTING

Secondary care was given to the participants. There were 2 participating centres, shopping malls in North and South Jeddah, Saudi Arabia.

PARTICIPANTS

We recruited 2686 participants over a 1-year study period. Participants were selected based on their willingness. The only criterion for exclusion was living in the area (North or South Jeddah) for less than 15 years.

PLANNED AND PRIMARY OUTCOME MEASURES

Participants were measured for blood sugar levels, blood pressure and body mass index. All participants were asked to fill out a questionnaire.

RESULTS

There was a positive association between longer sleep duration and obesity, hypertension and hyperglycaemia. The adjusted ORs for obesity, hypertension and hyperglycaemia were 1.54 (95% CI 1.20 to 1.98), 1.89 (95% CI 1.45 to 2.48) and 1.59 (95% CI 1.19 to 2.13), respectively, in participants sleeping >8 h/night, as compared with those sleeping 7 h. The positive associations between longer sleep duration, defined as sleeping >7 h, and the disease status, did not differ from other risk factors such as physical activity and nutrition.

CONCLUSIONS

This is the first epidemiological study reporting on the association between sleep duration and cardiometabolic risk factors of MtS in a Saudi Arabian population. Sleep durations of 8 h or greater were found to be associated with all 3 cardiometabolic risk factors: obesity, hypertension and hyperglycaemia, and this relationship was not confounded by quality of nutrition or physical activity levels.

Sleep fragmentation and sepsis differentially impact blood-brain barrier integrity and transport of tumor necrosis factor-α in aging

The factors by which aging predisposes to critical illness are varied, complex, and not well understood. Sepsis is considered a quintessential disease of old age because the incidence and mortality of severe sepsis increases in old and the oldest old individuals. Aging is associated with dramatic changes in sleep quality and quantity and sleep increasingly becomes fragmented with age. In healthy adults, sleep disruption induces inflammation. Multiple aspects of aging and of sleep dysregulation interact via neuroimmune mechanisms. Tumor necrosis factor-α (TNF), a cytokine involved in sleep regulation and neuroimmune processes, exerts some of its effects on the CNS by crossing the blood-brain barrier (BBB). In this study we examined the impact of sepsis, sleep fragmentation, and aging on BBB disruption and TNF transport into brain. We used the cecal ligation and puncture (CLP) model of sepsis in young and aged mice that were either undisturbed or had their sleep disrupted. There was a dichotomous effect of sepsis and sleep disruption with age: sepsis disrupted the BBB and increased TNF transport in young mice but not in aged mice, whereas sleep fragmentation disrupted the BBB and increased TNF transport in aged mice, but not in young mice. Combining sleep fragmentation and CLP did not produce a greater effect on either of these BBB parameters than did either of these manipulations alone. These results suggest that the mechanisms by which sleep fragmentation and sepsis alter BBB functions are fundamentally different from one another and that a major change in the organism's responses to those insults occurs with aging.

Maternal sleep duration and complaints of vital exhaustion during pregnancy is associated with placental abruption

OBJECTIVE

Sleep disorders are associated with cardiovascular complications and preterm delivery (PTD). Insufficient sleep results in metabolic alterations and increased inflammation, both known to contribute to placental abruption (abruption), a determinant of PTD. We examined associations of abruption with sleep duration and complaints of vital exhaustion.

METHODS

The study included 164 abruption cases and 160 controls in a multicenter study in Peru. Data on habitual sleep duration and vital exhaustion during the first 6 months of pregnancy were elicited during interviews conducted following delivery. Women were categorized according to short, normal and long sleep duration (≤6, 7-8 and ≥9 h); and frequency of feeling exhausted. Odds ratios (OR) and 95% confidence intervals (CI) were calculated.

RESULTS

Short and long sleep durations were associated with increased odds of abruption. The ORs of abruption in relation to short (≤6 h) and long (≥9 h) sleep duration were 2.0 (95% CI 1.1-3.7) and 2.1 (95% CI 1.1-4.1), compared with normal sleep duration (7-8 h). Complaints of vital exhaustion were also associated with abruption (OR = 2.37; 95% CI 1.46-3.85), and were independent of sleep duration.

CONCLUSION

We extend the existing literature and support the thesis that maternal sleep habits and disorders should be assessed among pregnant women.

Sickness behaviour after lipopolysaccharide treatment in ghrelin deficient mice

Ghrelin is an orexigenic hormone produced mainly by the gastrointestinal system and the brain. Much evidence also indicates a role for ghrelin in sleep and thermoregulation. Further, ghrelin was recently implicated in immune system modulation. Administration of bacterial lipopolysaccharide (LPS) induces fever, anorexia, and increased non-rapid-eye movement sleep (NREMS) and these actions are mediated primarily by proinflammatory cytokines. Ghrelin reduces LPS-induced fever, suppresses circulating levels of proinflammatory cytokines and reduces the severity and mortality of various models of experimental endotoxemia. In the present study, we determined the role of intact ghrelin signaling in LPS-induced sleep, feeding, and thermoregulatory responses in mice. Sleep-wake activity was determined after intraperitoneal, dark onset administration of 0.4, 2 and 10 μg LPS in preproghrelin knockout (KO) and wild-type (WT) mice. In addition, body temperature, motor activity and changes in 24-h food intake and body weight were measured. LPS induced dose-dependent increases in NREMS, and suppressed rapid-eye movement sleep, electroencephalographic slow-wave activity, motor activity, food intake and body weight in both Ppg KO and WT mice. Body temperature changes showed a biphasic pattern with a decrease during the dark period followed by an increase in the light phase. The effects of the low and middle doses of LPS were indistinguishable between the two genotypes. Administration of 10 μg LPS, however, induced significantly larger changes in NREMS and wakefulness amounts, body temperature, food intake and body weight in the Ppg KO mice. These findings support a role for ghrelin as an endogenous modulator of inflammatory responses and a central component of arousal and feeding circuits.

Sleep disturbance, cytokines, and fatigue in women with ovarian cancer

Pro-inflammatory cytokines, such as interleukin-6 (IL-6), have been implicated in the underlying processes contributing to sleep regulation and fatigue. Despite evidence for sleep difficulties, fatigue, and elevations in IL-6 among women with ovarian cancer, the association between these symptoms and IL-6 has not been investigated. To address this knowledge gap, we examined relationships between sleep disturbance, fatigue, and plasma IL-6 in 136 women with ovarian cancer prior to surgery. These relationships were also examined in 63 of these women who were disease-free and not receiving chemotherapy one year post-diagnosis. At both time-points, higher levels of IL-6 were significantly associated with sleep disturbances (p<0.05), controlling for potentially confounding biological and psychosocial covariates. Higher IL-6 was significantly associated with fatigue prior to surgery (p<0.05); however, when sleep disturbance was included in the model, the relationship was no longer significant. IL-6 was not significantly associated with fatigue at one year. Changes in sleep over time were significantly associated with percent change in IL-6 from pre-surgery to one year, adjusting for covariates (p<0.05). These findings support a direct association of IL-6 with sleep disturbances in this population, whereas the relationship between IL-6 and fatigue prior to surgery may be mediated by poor sleep. As this study is the first to examine cytokine contributions to sleep and fatigue in ovarian cancer, further research is warranted to clarify the role of biological correlates of sleep and fatigue in this population.

TNF-α and temporal changes in sleep architecture in mice exposed to sleep fragmentation

TNF-α plays critical roles in host-defense, sleep-wake regulation, and the pathogenesis of various disorders. Increases in the concentration of circulating TNF-α after either sleep deprivation or sleep fragmentation (SF) appear to underlie excessive daytime sleepiness in patients with sleep apnea (OSA). Following baseline recordings, mice were subjected to 15 days of SF (daily for 12 h/day from 07.00 h to 19.00 h), and sleep parameters were recorded on days1, 7 and 15. Sleep architecture and sleep propensity were assessed in both C57BL/6J and in TNF-α double receptor KO mice (TNFR KO). To further confirm the role of TNF-α, we also assessed the effect of treatment with a TNF- α neutralizing antibody in C57BL/6J mice. SF was not associated with major changes in global sleep architecture in C57BL/6J and TNFR KO mice. TNFR KO mice showed higher baseline SWS delta power. Further, following 15 days of SF, mice injected with TNF-α neutralizing antibody and TNFR KO mice showed increased EEG SWS activity. However, SWS latency, indicative of increased propensity to sleep, was only decreased in C57BL/6J, and was unaffected in TNFR KO mice as well as in C57BL/6J mice exposed to SF but treated with TNF-α neutralizing antibody. Taken together, our findings show that the excessive sleepiness incurred by recurrent arousals during sleep may be due to activation of TNF-alpha-dependent inflammatory pathways, despite the presence of preserved sleep duration and global sleep architecture.

The TNF Receptors p55 and p75 Mediate Chemotaxis of PMN Induced by TNFalpha and a TNFalpha 36-62 Peptide

The present study was performed to examine whether residues 36–62 of TNFα contain the chemotactic domain of TNFα, and whether the p55 and p75 TNF receptors are involved in TNFα induced chemotaxis. The chemotactic effect of TNFα on PMN was inhibited by the mAbs Hrt-7b and Utr-1, against the p55 and p75 TNF receptors, respectively. Both receptors may therefore be required for mediating the chemotactic effect of TNFcz. The synthetic TNFα 36–62, similar to TNFα, had chemotactic effects on both PMN and monocytes. The chemotactic activity of the TNFα 36–62 peptide on PMN, was inhibited by Htr-7b, Utr-1 and soluble p55 receptor, which shows that the peptide possessed the ability to induce chemotaxis through the TNF receptors. In contrast to TNFα, the peptide did not show a cytotoxic activity against WEHI 164 flbrosarcoma cells. It is suggested that different domains of the TNFα molecule induce distinct biological effects.

Cytokines, neurophysiology, neuropsychology, and psychiatric symptoms

Recent research has overcome the old paradigms of the brain as an immunologically privileged organ, and of the exclusive role of neurotransmitters and neuropeptides as signal transducers in the central nervous system. Growing evidence suggests that the signal proteins of the immune system - the cytokines - are also involved in modulation of behavior and induction of psychiatric symptoms. This article gives an overview on the nature of cytokines and the proposed mechanisms of immune-to-brain interaction. The role of cytokines in psychiatric symptoms, syndromes, and disorders like sickness behavior, major depression, and schizophrenia are discussed together with recent immunogenetic findings.

Obstructive sleep apnea syndrome and perioperative complications: a systematic review of the literature

Obstructive sleep apnea syndrome (OSAS) is a common sleep related breathing disorder. Its prevalence is estimated to be between 2% and 25% in the general population. However, the prevalence of sleep apnea is much higher in patients undergoing elective surgery. Sedation and anesthesia have been shown to increase the upper airway collapsibility and therefore increasing the risk of having postoperative complications in these patients. Furthermore, the majority of patients with sleep apnea are undiagnosed and therefore are at risk during the perioperative period. It is important to identify these patients so that appropriate actions can be taken in a timely fashion. In this review article, we will discuss the epidemiology of sleep apnea in the surgical population. We will also discuss why these patients are at a higher risk of having postoperative complications, with the special emphasis on the role of anesthesia, opioids, sedation, and the phenomenon of REM sleep rebound. We will also review how to identify these patients preoperatively and the steps that can be taken for their perioperative management.

Repletion of TNFα or leptin in calorically restricted mice suppresses post-restriction hyperphagia

The causes of post-restriction hyperphagia (PRH) represent a target for drug-based therapies to prevent obesity. However, the factors causing PRH are poorly understood. We show that, in mice, the extent of PRH was independent of the time under restriction, but depended on its severity, suggesting that PRH was driven by signals from altered body composition. Signals related to fat mass were important drivers. Circulating levels of leptin and TNFα were significantly depleted following caloric restriction (CR). We experimentally repleted their levels to match those of controls, and found that in both treatment groups the level of PRH was significantly blunted. These data establish a role for TNFα and leptin in the non-pathological regulation of energy homeostasis. Signals from adipose tissue, including but not limited to leptin and TNFα, regulate PRH and might be targets for therapies that support people engaged in CR to reduce obesity.

Adiponectin deficiency: role in chronic inflammation induced colon cancer

Adiponectin (APN), an adipokine, exerts an anti-inflammatory and anti-cancerous activity with its role in glucose and lipid metabolism and its absence related to several obesity related malignancies including colorectal cancer. The aim of this study is to determine the effect of APN deficiency on the chronic inflammation-induced colon cancer. This was achieved by inducing inflammation and colon cancer in both APN knockout (KO) and C57B1/6 wild type (WT) mice. They were divided into four treatment groups (n=6): 1) control (no treatment); 2) treatment with three cycles of dextran sodium sulfate (DSS); 3) weekly doses of 1,2-dimethylhydrazine (DMH) (20mg/kg of mouse body weight) for twelve weeks; 4) a single dose of DMH followed by 3 cycles of DSS (DMH+DSS). Mice were observed for diarrhea, stool hemoccult, and weight loss and were sacrificed on day 153. Tumor area and number were counted. Colonic tissues were collected for Western blot and immunohistochemistry analyses. APNKO mice were more protected than WT mice from DSS induced colitis during first DSS cycle, but lost this protection during the second and the third DSS cycles. APNKO mice had significantly severe symptoms and showed greater number and larger area of tumors with higher immune cell infiltration and inflammation than WT mice. This result was further confirmed by proteomic study including pSTAT3, pAMPK and Cox-2 by western blot and Immunohistochemistry. Conclusively, APN deficiency contributes to inflammation-induced colon cancer. Hence, APN may play an important role in colorectal cancer prevention by modulating genes involved in chronic inflammation and tumorigenesis.

Tumor necrosis factor-alpha regulates the Hypocretin system via mRNA degradation and ubiquitination

Recent studies recognize that Hypocretin system (also known as Orexin) plays a critical role in sleep/wake disorders and feeding behaviors. However, little is known about the regulation of the Hypocretin system. It is also known that tumor necrosis factor alpha (TNF-α) is involved in the regulation of sleep/wake cycle. Here, we test our hypothesis that the Hypocretin system is regulated by TNF-α. Prepro-Hypocretin and Hypocretin receptor 2 (HcrtR2) can be detected at a very low level in rat B35 neuroblastoma cells. In response to TNF-α, Prepro-Hypocretin mRNA and protein levels are down-regulated, and also HcrtR2 protein level is down-regulated in B35 cells. To investigate the mechanism, exogenous rat Prepro-Hypocretin and rat HcrtR2 were overexpressed in B35 cells. In response to TNF-α, protein and mRNA of Prepro-Hypocretin are significantly decreased (by 93% and 94%, respectively), and the half-life of Prepro-Hypocretin mRNA is decreased in a time- and dose-dependent manner. The level of HcrtR2 mRNA level is not affected by TNF-α treatment; however, HcrtR2 protein level is significantly decreased (by 86%) through ubiquitination in B35 cells treated with TNF-α. Downregulation of cellular inhibitor of apoptosis protein-1 and -2 (cIAP-1 and -2) abrogates the HcrtR2 ubiquitination induced by TNF-α. The control green fluorescent protein (GFP) expression is not affected by TNF-α treatment. These studies demonstrate that TNF-α can impair the function of the Hypocretin system by reducing the levels of both Prepro-Hypocretin and HcrtR2.

Associations of early pregnancy sleep duration with trimester-specific blood pressures and hypertensive disorders in pregnancy

STUDY OBJECTIVES

We evaluated the influence of maternal self-reported habitual sleep duration during early pregnancy on blood pressure (BP) levels and risk of hypertensive disorders of pregnancy.

DESIGN

Prospective cohort study.

SETTING

Clinic-based study.

PARTICIPANTS

A cohort of 1,272 healthy, pregnant women.

MEASUREMENTS AND RESULTS

We abstracted maternal antenatal BP values from medical records and estimated mean BP differences across hours of sleep categories in regression models, using generalized estimating equations. Odds ratios (OR) and 95% confidence intervals (95% CIs) for pregnancy induced hypertension (PIH) and preeclampsia (PE) in relation to long and short sleep duration were estimated. Mean 1st and 2nd trimester systolic (S) and diastolic (D) BP values were similar among women reporting to be short sleepers (< or = 6 h) vs. women reporting to sleep 9 hours. However, both short and long sleep duration in early pregnancy were associated with increased mean 3rd trimester SBP and DBP. For example, mean 3rd trimester SBP was 3.72, and 2.43 mm Hg higher for women reporting < or = 6 h and 7-8 h sleep, respectively, compared with women reporting 9 h of sleep. Mean 3rd trimester SBP was 4.21 mm Hg higher for women reporting long sleep (> or = 10 h) vs. the reference group. Short and long sleep durations were associated with increased risks of PIH and PE. The ORs for very short (< 5 h) and long (> or = 10 h) sleepers were 9.52 (95% CI 1.83 to 49.40) and 2.45 (95% CI 0.74 to 8.15) for PE.

CONCLUSIONS

Our findings are consistent with a larger literature that documents elevated blood pressure and increased risks of hypertension with short and long sleep duration.

Sleep-disordered breathing in obese children is associated with prevalent excessive daytime sleepiness, inflammation, and metabolic abnormalities

BACKGROUND

In obese adults, sleep apnea is associated with excessive daytime sleepiness (EDS) and cardiometabolic risk factors. In children, on the other hand, sleep-disordered breathing (SDB) is primarily associated with anatomic abnormalities and neurocognitive impairment, whereas studies on potential concurrent metabolic aberrations and EDS have been limited and inconsistent. In this study, we examined the joint effect of SDB and obesity in EDS as well as proinflammatory and metabolic markers.

METHODS

One hundred fifty children, aged 5-17 yr, were consecutively recruited from our sleep disorders clinic and a subset of the Penn State Children's Cohort. Every child had a thorough history and physical examination, 9-h polysomnographic study, and a single blood draw for the assessment of IL-6, TNFalpha, soluble IL-6 receptor, TNF receptor-1, hypersensitive C-reactive protein, leptin, and adiponectin. In addition, parents completed a subjective questionnaire to assess EDS. Analysis of covariance was performed on four groups that were separated by SDB severity and body mass index.

RESULTS

EDS frequency increased progressively and significantly in the four groups. There was a significant linear trend in plasma IL-6, TNF receptor-1, hypersensitive C-reactive protein, and leptin concentrations, with lowest levels observed in lean controls and highest in overweight/obese with moderate SDB. Adiponectin followed the opposite pattern.

CONCLUSIONS

This study suggests that in a clinical sample of obese children, SDB is associated with EDS, elevation of proinflammatory cytokines, increased leptin, and decreased adiponectin. All these changes point to an inflammatory/insulin resistance state, suggesting that SDB in obese children share many similarities with SDB in obese adults.

Acquired genetic and functional alterations associated with transforming growth factor beta type I resistance in Hep3B human hepatocellular carcinoma cell line

During the neoplastic process tumour cells frequently acquire resistance to the antiproliferative signals of transforming growth factor-β (TGF-β). Here we examined a human hepatocellular carcinoma cell line (Hep3B-TS) sensitive to TGF-β signalling, and a derivative line (Hep3B-TR) rendered resistant to TGF-β by stepwise exposure to TGF-β₁. Comprehensive molecular cytogenetic analysis revealed that the acquisition of TGF-β-resistance by Hep3B-TR cells was due to loss of TGF-β receptor 2 (TGFβRII) gene. As demonstrated by spectral karyotyping and array-based comparative genomic hybridization, and in difference to Hep3B-TS cells, which have three rearranged and two normal copies of chromosome 3 that harbour the TGFβRII gene, Hep3B-TR cells have four rearranged and one apparently normal chromosome 3, which nonetheless underwent a critical microdeletion at the site of TGFβRII gene. Gene expression analysis using an oligonucleotide microarray of 21,397 genes showed that Hep3B-TR differentially expressed 307 genes, out of which 197 and 110 were up- and down-regulated, respectively, compared to Hep3B-TS. Six of differentially expressed genes were identified as downstream targets of the tumour necrosis factor (TNF) gene, suggesting that loss of TGFβRII triggered activation of the TNF pathway known to be regulated by TGF-β₁ network. On the functional level, the TGF-β-resistant Hep3B-TR cells displayed significantly enhanced capacity for anchorage independent growth and cell migration in vitro, and also increased tumorigenicity in vivo and in vitro and in vivo tumorigenicity compared with parental sensitive cells.

Sickness behaviour pushed too far--the basis of the syndrome seen in severe protozoal, bacterial and viral diseases and post-trauma

Certain distinctive components of the severe systemic inflammatory syndrome are now well-recognized to be common to malaria, sepsis, viral infections, and post-trauma illness. While their connection with cytokines has been appreciated for some time, the constellation of changes that comprise the syndrome has simply been accepted as an empirical observation, with no theory to explain why they should coexist. New data on the effects of the main pro-inflammatory cytokines on the genetic control of sickness behaviour can be extended to provide a rationale for why this syndrome contains many of its accustomed components, such as reversible encephalopathy, gene silencing, dyserythropoiesis, seizures, coagulopathy, hypoalbuminaemia and hypertriglyceridaemia. It is thus proposed that the pattern of pathology that comprises much of the systemic inflammatory syndrome occurs when one of the usually advantageous roles of pro-inflammatory cytokines – generating sickness behaviour by moderately repressing genes (Dbp, Tef, Hlf, Per1, Per2 and Per3, and the nuclear receptor Rev-erbα) that control circadian rhythm – becomes excessive. Although reversible encephalopathy and gene silencing are severe events with potentially fatal consequences, they can be viewed as having survival advantages through lowering energy demand. In contrast, dyserythropoiesis, seizures, coagulopathy, hypoalbuminaemia and hypertriglyceridaemia may best be viewed as unfortunate consequences of extreme repression of these same genetic controls when the pro-inflammatory cytokines that cause sickness behaviour are produced excessively. As well as casting a new light on the previously unrationalized coexistence of these aspects of systemic inflammatory diseases, this concept is consistent with the case for a primary role for inflammatory cytokines in their pathogenesis across this range of diseases.

Cytokine mRNA induction by interleukin-1beta or tumor necrosis factor alpha in vitro and in vivo

Hypothalamic and cortical mRNA levels for cytokines such as interleukin-1beta (IL1beta), tumor necrosis factor alpha (TNFalpha), nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) are impacted by systemic treatments of IL1beta and TNFalpha. To investigate the time course of the effects of IL1beta and TNFalpha on hypothalamic and cortical cytokine gene expression, we measured mRNA levels for IL1beta, TNFalpha, interleukin-6 (IL-6), interleukin-10 (IL-10), IL1 receptor 1, BDNF, NGF, and glutamate decarboxylase-67 in vitro using hypothalamic and cortical primary cultures. IL1beta and TNFalpha mRNA levels increased significantly in a dose-dependent fashion after exposure to either IL1beta or TNFalpha. IL1beta increased IL1beta mRNA in both the hypothalamic and cortical cultures after 2-6 h while TNFalpha mRNA increased significantly within 30 min and continued to rise up to 2-6 h. Most of the other mRNAs showed significant changes independent of dose in vitro. In vivo, intracerebroventricular (icv) injection of IL1beta or TNFalpha also significantly increased IL1beta, TNFalpha and IL6 mRNA levels in the hypothalamus and cortex. IL1beta icv, but not TNFalpha, increased NGF mRNA levels in both these areas. Results support the hypothesis that centrally active doses of IL1beta and TNFalpha enhance their own mRNA levels as well as affect mRNA levels for other neuronal growth factors.

Effects of ghrelin on neuronal survival in cells derived from dorsal motor nucleus of the vagus

BACKGROUND

The effects of intestinal inflammation on the central neurons projecting to the enteric nervous system are unknown. The dorsal motor nucleus of the vagus signals to the gastrointestinal system. Ghrelin is elevated in patients with inflammatory bowel disease and has been implicated as an inflammatory mediator. The purpose of this study was to investigate the effects of gastrointestinal inflammation on the dorsal motor nucleus of the vagus in rats, as well as the effects of proinflammatory cytokines and ghrelin on neurons from the dorsal motor nucleus of the vagus in vitro.

METHODS

DiI was injected into the stomach wall of rats to retrogradely label neurons of the dorsal motor nucleus of the vagus. Intestinal inflammation was induced with indomethacin injection. Serial serum ghrelin measurements were performed. Tissue was examined under fluorescent microscopy. In vitro studies using primary culture of neurons from the dorsal motor nucleus of the vagus were performed. Reverse transcriptase-polymerase chain reaction for cytokine transcripts and immunohistochemistry for cytokine receptors were performed. Cell proliferation and apoptosis were measured by enzyme-linked immunosorbent assay.

RESULTS

A significant decrease of DiI labeling was demonstrated in the dorsal motor nucleus of the vagus of animals injected with indomethacin. Serum levels of ghrelin were significantly elevated 2 days after induction of inflammation. In vitro, apoptosis and cell proliferation were measured after 24-hour exposure to experimental conditions. Ghrelin alone had no effect on apoptosis. Exposure to interleukin (IL)-1 beta or tumor necrosis factor (TNF)-alpha increased apoptosis. The addition of ghrelin to cytokine resulted in significant decreases in apoptosis compared to cytokine alone. Ghrelin significantly increased neuronal proliferation. Exposure to IL-1 beta, IL-6, or TNF-alpha significantly decreased proliferation. The addition of ghrelin to TNF-alpha or IL-6 significantly increased cellular proliferation compared to cytokine alone.

CONCLUSIONS

Neurons from the dorsal motor nucleus of the vagus that project to the stomach are reduced in number after induction of colitis in rats. In vitro, proinflammatory cytokines increase apoptosis and decrease cell proliferation of neurons from the dorsal motor nucleus of the vagus. These effects are attenuated by ghrelin.

A cyclooxygenase-2 inhibitor attenuates spontaneous and TNF-alpha-induced non-rapid eye movement sleep in rabbits

Sleep is regulated in part by the brain cytokine network, including tumor necrosis factor-alpha (TNF-alpha). TNF-alpha activates the transcription factor nuclear factor-kappaB, which in turn promotes transcription of many genes, including cyclooxygenase-2 (COX-2). COX-2 is in the brain and is an enzyme responsible for production of prostaglandin D2. The hypothesis that central COX-2 plays a role in the regulation of spontaneous and TNF-alpha-induced sleep was investigated. Three doses (0.5, 5, and 50 microg) of NS-398, a highly selective COX-2 inhibitor, were injected intracerebroventricularly. The highest dose decreased non-rapid eye movement sleep. The intermediate and highest doses decreased electroencephalographic slow-wave activity; the greatest reduction occurred after 50 microg of NS-398 during the first 3-h postinjection period. Rapid eye movement sleep and brain temperature were not altered by any dose of NS-398. Pretreatment of rabbits with 5 or 50 microg of NS-398 blocked the TNF-alpha-induced increases in non-rapid eye movement sleep, electroencephalographic slow-wave activity, and brain temperature. These data suggest that COX-2 is involved in the regulation of spontaneous and TNF-alpha-induced sleep.

Interleukin-15 and interleukin-2 enhance non-REM sleep in rabbits

Interleukin (IL)-15 and -2 share receptor- and signal-transduction pathway (Jak-STAT pathway) components. IL-2 is somnogenic in rats but has not been tested in other species. Furthermore, the effects of IL-15 on sleep have not heretofore been described. We investigated the somnogenic actions of IL-15 in rabbits and compared them with those of IL-2. Three doses of IL-15 or -2 (10, 100, and 500 ng) were injected intracerebroventriculary at the onset of the dark period. In addition, 500 ng of IL-15 and -2 were injected 3 h after the beginning of the light period. IL-15 dose dependently increased non-rapid eye movement sleep (NREMS) and induced fever. IL-15 inhibited rapid eye movement sleep (REMS) after its administration during the light period; however, all doses of IL-15 failed to affect REMS if given at dark onset. IL-2 also dose dependently increased NREMS and fever. IL-2 inhibited REMS, and this effect was observed only in the light period. IL-15 and -2 enhanced electroencephalographic (EEG) slow waves during the initial 9-h postinjection period, then, during hours 10-23 postinjection, reduced EEG slow-wave activity. Current data support the notion that the brain cytokine network is involved in the regulation of sleep.

Glial cell line-derived neurotrophic factor promotes sleep in rats and rabbits

Various growth factors (e.g., growth hormone-releasing hormone, acidic fibroblast growth factor, nerve growth factor, brain-derived neurotrophic factor, and interleukin-1) are implicated in sleep regulation. It is hypothesized that neuronal activity enhances the production of such growth factors, and they in turn form part of the sleep regulatory mechanism. Glial cell line-derived neurotrophic factor (GDNF) promotes development, differentiation, maintenance, and regeneration of neurons, and its production is induced by well-characterized sleep regulatory substances such as interleukin-1 and tumor necrosis factor. Therefore, we investigated whether GDNF would promote sleep. Twenty-six male Sprague-Dawley rats and 30 male New Zealand White rabbits were surgically implanted with electroencephalogram (EEG) and electromyogram (EMG; rats only) electrodes, a brain thermistor, and a lateral intracerebroventricular cannula. The animals were injected intracerebroventricularly with pyrogen-free saline and on a separate day with one of the following doses of GDNF: 5, 50, and 500 ng in rabbits and 50 and 500 ng in rats. The EEG, brain temperature, EMG (in rats), and motor activity (in rabbits) were recorded for 23 h after the intracerebroventricular injection. GDNF (500-ng dose) increased the time spent in nonrapid eye movement sleep in both rats and rabbits. Rapid eye movement sleep was not affected by the lower doses of GDNF but was inhibited in rabbits after the high dose. EEG slow-wave activity was not affected by GDNF. The current results provide further evidence that various growth factors are involved in sleep regulation.

Vagotomy attenuates tumor necrosis factor-alpha-induced sleep and EEG delta-activity in rats

Much evidence suggests that tumor necrosis factor-alpha (TNF-alpha) is involved in the regulation of physiological sleep. However, it remains unclear whether peripheral administration of TNF-alpha induces sleep in rats. Furthermore, the role of the vagus nerve in the somnogenic actions of TNF-alpha had not heretofore been studied. Four doses of TNF-alpha were administered intraperitoneally just before the onset of the dark period. The three higher doses of TNF-alpha (50, 100, and 200 microg/kg) dose dependently increased nonrapid eye movement sleep (NREMS), accompanied by increases in electroencephalogram (EEG) slow-wave activity. TNF-alpha increased EEG delta-power and decreased EEG alpha- and beta-power during the initial 3 h after injection. In vagotomized rats, the NREMS responses to 50 or 100 microg/kg of TNF-alpha were attenuated, while significant TNF-alpha-induced increases in NREMS were observed in a sham-operated group. Moreover, the vagotomized rats failed to exhibit the increase in EEG delta-power induced by TNF-alpha intraperitoneally. These results suggest that peripheral TNF-alpha can induce NREMS and vagal afferents play an important role in the effects of peripheral TNF-alpha and EEG synchronization on sleep. Intraperitoneal TNF-alpha failed to affect brain temperature at the doses tested, thereby demonstrating that TNF-alpha-induced sleep effects are, in part, independent from its effects on brain temperature. Results are consistent with the hypothesis that a cytokine network is involved in sleep regulation.

c-Fos generation in the dorsal vagal complex after systemic endotoxin is not dependent on the vagus nerve

The present study used activation of the c-Fos oncogene protein within neurons in the dorsal vagal complex (DVC) as a marker of neuronal excitation in response to systemic endotoxin challenge [i.e. , lipopolysaccharide (LPS)]. Specifically, we investigated whether vagal connections with the brain stem are necessary for LPS cytokine- induced activation of DVC neurons. Systemic exposure to LPS elicited a significant activation of c-Fos in neurons in the nucleus of the solitary tract (NST) and area postrema of all thiobutabarbital-anesthetized rats examined, regardless of the integrity of their vagal nerves. That is, rats with both vagi cervically transected were still able to respond with c-Fos activation of neurons in the DVC. Unilateral cervical vagotomy produced a consistent but small reduction in c-Fos activation in the ipsilateral NST of all animals within this experimental group. Given that afferent input to the NST is exclusively excitatory, it is not surprising that unilateral elimination of all vagal afferents would diminish NST responsiveness (on the vagotomized side). These data lead us to conclude that the NST itself is a primary central nervous system detector of cytokines.

TNF-alpha activates solitary nucleus neurons responsive to gastric distension

Tumor necrosis factor-alpha (TNF-alpha) is liberated as part of the immune response to antigenic challenge, carcinogenesis, and radiation therapy. Previous studies have implicated elevated circulating levels of this cytokine in the gastric hypomotility associated with these disease states. Our earlier studies suggest that a site of action of TNF-alpha may be within the medullary dorsal vagal complex. In this study, we describe the role of TNF-alpha as a neuromodulator affecting neurons in the nucleus of the solitary tract that are involved in vago-vagal reflex control of gastric motility. The results presented herein suggest that TNF-alpha may induce a persistent gastric stasis by functioning as a hormone that modulates intrinsic vago-vagal reflex pathways during illness.

Interleukin-13 and transforming growth factor-beta1 inhibit spontaneous sleep in rabbits

Proinflammatory cytokines, including interleukin-1beta and tumor necrosis factor-alpha are involved in physiological sleep regulation. Interleukin (IL)-13 and transforming growth factor (TGF)-beta1 are anti-inflammatory cytokines that inhibit proinflammatory cytokines by several mechanisms. Therefore, we hypothesized that IL-13 and TGF-beta1 could attenuate sleep in rabbits. Three doses of IL-13 (8, 40, and 200 ng) and TGF-beta1 (40, 100, and 200 ng) were injected intracerebroventricularly 3 h after the beginning of the light period. In addition, one dose of IL-13 (200 ng) and one dose of TGF-beta1 (200 ng) were injected at dark onset. The two higher doses of IL-13 and the highest dose of TGF-beta1 significantly inhibited spontanenous non-rapid eye movement sleep (NREMS) when they were given in the light period. IL-13 also inhibited NREMS after dark onset administration; however, the inhibitory effect was less potent than that observed after light period administration. The 40-ng dose of IL-13 inhibited REMS duration during the dark period. TGF-beta1 administered at dark onset had no effect on sleep. These data provide additional evidence for the hypothesis that a brain cytokine network is involved in regulation of physiological sleep.

Dose-dependent effects of endotoxin on human sleep

The role of the central nervous system in the host response to infection and inflammation and modulation of these responses by the hypothalamic-pituitary-adrenal system are well established. In animals, activation of host defense mechanisms increases non-rapid eye movement (NREM) sleep amount and intensity, which, in turn, are thought to support host defense, or the body's ability to defend itself against challenges to its immune system. In humans, the evidence is conflicting. Therefore, we investigated the effects of three placebo-controlled doses of endotoxin on host response, including nocturnal sleep in healthy volunteers. Administered before nocturnal sleep onset, endotoxin dose dependently increased rectal temperature, heart rate, and the plasma levels of tumor necrosis factor (TNF)-alpha, soluble TNF receptors, interleukin (IL)-1 receptor antagonist, IL-6, and cortisol. The lowest dose reliably increased circulating levels of cytokines and soluble cytokine receptors, but it did not affect rectal temperature, heart rate, or cortisol. This subtle host defense activation increased deep NREM sleep amount, often referred to as slow-wave sleep (stages 3 and 4), and intensity (delta power). Conversely, the highest dose of endotoxin disrupted sleep. Whereas it is well established that the endocrine and thermoregulatory systems are very sensitive to endotoxin, this study shows that human sleep-wake behavior is even more sensitive to activation of host defense mechanisms.

Neutralization of pyrogen-induced tumour necrosis factor by its type 1 soluble receptor in guinea-pigs: effects on fever and interleukin-6 release

1. A soluble form of the tumour necrosis factor (TNF) type 1 receptor (referred to as TNF binding protein, TNF-bp) at a dose of 1 mg per animal, or an equivalent volume of solvent, was injected together with 10 microg kg-1 lipopolysaccharide (LPS) or 50 microg kg-1 muramyl-dipeptide (MDP) directly into the arterial circulation of guinea-pigs and the effects on circulating TNF or interleukin-6 (IL-6) and on abdominal temperature were studied. 2. At 15 or 60 min after injection, LPS-induced and MDP-induced circulating TNF was below the detection limit of the assay and thus completely neutralized in animals treated with TNF-bp. In the control group, TNF was still below the limit of detection in most animals 15 min after LPS was injected; in some animals small traces of TNF could already be detected at that time. However, 60 min after administration of LPS, large amounts of TNF (19508 +/- 4682 pg ml-1) were measured in the control group. MDP-induced TNF in plasma was below the limit of detection 15 min after MDP was injected, and rose to 10862 +/- 3029 pg ml-1 60 min after injection. 3. Low levels of circulating IL-6 (20-40 international units (IU) ml-1) were measured in all groups of animals 15 min after injection of LPS or MDP. This value corresponds to the baseline activity of IL-6 in plasma of guinea-pigs. One hour after administration of LPS, IL-6 rose to 5442 +/- 1662 IU ml-1 in the control group and to a significantly lower value of 1485 +/- 179 IU ml-1 in guinea-pigs treated with TNF-bp. One hour after injection of MDP, circulating IL-6 was 2614 +/- 506 IU ml-1 in the control group, while the corresponding value in animals treated with TNF-bp again was significantly lower (873 +/- 312 IU ml-1). 4. The second phase of the characteristic biphasic LPS fever in guinea-pigs was significantly attenuated in animals treated with TNF-bp. The shorter first phase of the febrile response to LPS was identical in both groups of animals. 5. The late phase of MDP-induced fever (7-22 h after injection) was depressed by treatment with TNF-bp, while the first phase of MDP-induced fever (0-7 h after injection) was significantly enhanced by the neutralization of TNF by TNF-bp.

Mice lacking the TNF 55 kDa receptor fail to sleep more after TNFalpha treatment

Tumor necrosis factor (TNF) is a well characterized sleep-regulatory substance. To study receptor mechanisms for the sleep-promoting effects of TNF, sleep patterns were determined in control and TNF 55 kDa receptor knock-out (TNFR-KO) mice with a B6 x 129 background after intraperitoneal injections of saline or murine TNFalpha. The TNFR-KO mice had significantly less baseline sleep than the controls. TNFalpha dose-dependently increased non-rapid eye movement sleep (NREMS) in the controls but did not influence sleep in TNFR-KO mice. Although TNFR-KO mice failed to respond to TNFalpha, they had an increase in NREMS and a decrease in rapid eye movement sleep after interleukin-1beta treatment. These results indicate that TNFalpha affects sleep via the 55 kDa receptor and provide further evidence that TNFalpha is involved in physiological sleep regulation. Current results also extend the list of species to mice in which TNFalpha and interleukin-1beta are somnogenic.

Major histocompatibility class II molecules in the CNS: increased microglial expression at the onset of narcolepsy in canine model

Human narcolepsy is a neurological disorder known to be closely associated with HLA-DR2 and DQB1*0602. Because most autoimmune diseases are HLA-associated, a similar mechanism has been proposed for narcolepsy. However, neither systemic nor CNS evidence of an autoimmune abnormality has ever been reported. In this study, major histocompatibility (MHC) class I and class II expression was studied in the CNS of human and canine narcoleptics using immunohistochemistry and Northern analysis. Results indicated that canine narcolepsy is associated with a significant increase of MHC class II expression by the microglia. Moreover, the highest values were found between 3 and 8 months of age, strikingly concomitant to the development of narcolepsy in the canine model. In humans, class II expression was not found significantly different between control and narcoleptic subjects. This result could be explained by the old age of the subjects (69.86 +/- 5.31 and 68.36 +/- 4.74 years in narcoleptics and controls, respectively), because class II expression is significantly correlated with age in both humans and dogs. For the first time, this study demonstrated that the expression of MHC class II molecules in the CNS is age-dependent and that a consistent increase of their expression by the microglia might be critically involved in the development of narcolepsy.

Inhibition of tumor necrosis factor in the brain suppresses rabbit sleep

Tumor necrosis factor (TNF) is a cytokine that possesses many biological activities, including enhancement of non-rapid-eye-movement sleep (NREMS). The role of endogenous TNF in the regulation of spontaneous sleep is unknown. If TNF is involved in sleep regulation, then reduction of endogenous TNF should suppress spontaneous sleep. A soluble TNF-binding protein I (TNF-BP I) and a synthetic fragment of TNF-BP I, TNF-R-(159-178), that contains the biologically active region of TNF-BP I, were used. These substances bind TNF and possess TNF-inhibitory activity; their effects on rabbit sleep after intracerebroventricular injection were determined across a 6-h recording period. Two doses of TNF-BP I (0.05 micrograms and 0.5 micrograms) were administered; the higher dose of TNF-BP I significantly decreased NREMS. Four doses of TNF-R-(159-178) (0.25 micrograms, 2.5 micrograms, 25 micrograms and 50 micrograms) were used. The 25 micrograms and 50 micrograms doses significantly suppressed NREMS. The highest dose (50 micrograms) also decreased REM sleep. These results are consistent with the hypothesis that endogenous brain TNF is involved in the regulation of normal sleep.

Peptidoglycan fragments decrease food intake and body weight gain in rats

We hypothesized that peptidoglycan (PG) fragments decrease appetite in rats. Male Lewis rats (150 g; n > or = 7) received intraperitoneal (i.p.) injections of purified soluble PG fragments that had been treated with polymyxin B-agarose to remove residual endotoxin. Food consumption and body weight gain were determined at intervals after injection. Single i.p. injections of macromolecular extensively O-acetylated PG (S-O-PG) and non-O-acetylated PG fragments (24 to 240 micrograms/kg) reduced food intake and body weight gain in a dose-dependent fashion during the first 12 h after injection. Low-molecular-weight disaccharide peptide monomers with nonreducing 1,6-anhydro-N-acetylmuramic acid ends and muramyl dipeptide (MDP; 1.6 mg/kg) were also appetite and weight gain suppressants, albeit at least 10-fold less potent than S-O-PG; however, muramidase-derived monomers and peptide cross-linked dimers with reducing muramic acid ends were inactive. Appetite suppression was not limited to the Lewis rat strain since another strain, F344, exhibited similar decreases in food intake after injection of S-O-PG or MDP. Oral administration of MDP or S-O-PG, at concentrations 3 and 20 times higher, respectively, than those that were active i.p., failed to elicit a hypophagic response. We conclude that soluble PG fragments are potent suppressants of food consumption and body weight gain in rats and that, although macromolecular PG is more potent than low-molecular-weight fragments, neither O-acetylation nor glycosidic linkage of PG fragments is required for activity. We speculate that PG fragments may contribute to loss of appetite during bacterial illness.