Serotonergic activation stimulates the pituitary-adrenal axis and alters interleukin-1 mRNA expression in rat brain

Sleep and Neuroimmunomodulation for Maintenance of Optimum Brain Function: Role of Noradrenaline

Immune function and sleep are two normal physiological processes to protect the living organism from falling sick. There is hardly any disease in which they remain unaffected, though the quantum of effect may differ. Therefore, we propose the existence of a strong correlation between sleep (quality or quantity) and immune response. This may be supported by the fact that sleep loss modulates many of the immunological molecules, which includes interferons; however, not much is known about their mechanism of action. Sleep is divided into rapid eye movement sleep (REMS) and non-REMS. For practical reasons, experimental studies have been conducted mostly by inducing loss of REMS. It has been shown that withdrawal of noradrenaline (NA) is a necessity for generation of REMS. Moreover, NA level increases in the brain upon REMS loss and the elevated NA is responsible for many of the sleep loss-associated symptoms. In this review, we describe how sleep (and its disturbance/loss) modulates the immune system by modulating the NA level in the brain or vice versa to maintain immune functions, physiological homeostasis, and normal healthy living. The increased levels of NA during REMS loss may cause neuroinflammation possibly by glial activation (as NA is a key modulator of microglia). Therefore, maintaining sleep hygiene plays a crucial role for a normal healthy living.

Sleep, immunity and shift workers: A review

To date, shift workers represent between 15% and 25% of the modern day workforce. Work time poses a great challenge to workers as it requires that they balance productivity and sleep time between shifts. As a result, these workers experience chronic sleep deprivation with increased fatigue and drowsiness due to this sleep deprivation. The impact of this kind of work on the immune system is not yet known. We conducted a literature review with the aim of evaluating articles on this specific type of work's effects on sleep and immunity.

Differential expression of rat hippocampal microRNAs in two rat models of chronic pain

The two most common forms of chronic pain are inflammatory pain and neuropathic pain. Nevertheless, the underlying mechanisms of these pain conditions and their therapeutic responses are poorly understood. MicroRNAs (miRNAs) negatively regulate cell genes, and thus control cell proliferation, inflammation and metabolism. In the present study, we examined gene expression in the hippocampus of rats in two models of chronic pain. In addition, we used the left hindpaw procedure to identify differences in the bilateral hippocampus. We divided the rats into the 4 following groups: the group with chronic constriction injury (CCI), the sham-operated group, the group injected with complete Freund's adjuvant (CFA) and the group injected with normal saline. miRNA expression profiles were analyzed using TaqMan low-density array (TLDA). We observed 54 miRNAs (22.7%) in the rats with CCI rats that were differentially expressed, including 7 miRNAs that were downregulated compared with the sham-operated rats. In the CFA-injected rats, 40 miRNAs (16.8%) were differentially expressed, including 8 miRNAs that were downregulated compared with the normal saline-injected rats. Pearson's correlation co-efficient for all detected miRNAs in the rat hippocampus failed to identify differences between the hippocampi bilaterally. An unsupervised cluster analysis produced separate clusters between the control and experimental groups. In this study, we demonstrate the differential expression of hippocampal miRNAs in two rat models of chronic pain; however, no significant differences were observed bilaterally in hippocampal miRNA expression. Further research is required to determine the correlation among miRNAs, messenger RNAs (mRNAs) and proteins.

The miRNA and mRNA changes in rat hippocampi after chronic constriction injury

OBJECTIVE

We elaborated the rat hippocampi in order to assess for central nervous system changes following a peripheral neuropathic injury.

DESIGN, SETTING, SUBJECTS

We examined the gene changes in the hippocampi of chronic constriction injury (CCI) rats with TaqMan® low-density array analysis (TLDA) and quantitative real-time polymerase chain reaction (qRT-PCR) of miR-125b, -132, and messenger RNAs (mRNAs) of neuropeptide Y, brain-derived neural factor, N-methyl-D-aspartate glutamate 2A receptor, gamma-aminobutyric acid A a1 receptor, gamma-aminobutyric acid A b1 receptor, gamma-aminobutyric acid B b2 receptor, serotonin 1A receptor, serotonin 2A receptor, serotonin 2C receptor, and serotonin 3A receptor on days 0, 7, and 15 after surgery.

INTERVENTIONS

None.

OUTCOME MEASURES

Two behavioral tests (thermal and mechanical stimulation tests) were performed three times at 5-minute intervals to assess pain thresholds. MicroRNA (miRNA) changes were examined by TLDA. mRNA changes were examined by qRT-PCR. Statistical significance was determined by Tukey-Kramer's method and paired t-test.

RESULTS

All rats showed mechanical and thermal hypersensitivity on the ipsilateral side. Out of 373 miRNAs analyzed, 237 were expressed, and 51 changed their expressions after CCI. By TLDA, cluster analysis found obvious miRNA changes on day 7 that tended to recover by day 15. For miR-125b, the relative expression decreased to 0.70 ± 0.30 at day 7 and recovered to 1.65 ± 0.19 at day 15. The miR-132 relative expressions were 0.69 ± 0.30 and 0.70 ± 0.15, respectively. The mRNA changes followed the miRNA changes.

CONCLUSIONS

Our results showed that the peripheral nerve injury altered rat hippocampal miRNA.

The efficacy of Hypericum perforatum (St John's wort) for the treatment of premenstrual syndrome: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Premenstrual syndrome (PMS) is a common condition. Some of the most widely prescribed medications are selective serotonin reuptake inhibitors (SSRIs), based on the hypothesized role of serotonin in the production of PMS symptoms. PMS sufferers, especially those experiencing mild to moderate symptoms, are often reluctant to take this form of medication and instead buy over-the-counter preparations to treat their symptoms, for which the evidence base with regard to efficacy is limited. Hypericum perforatum (St John's wort) influences the serotonergic system. As such, this widely available herbal remedy deserves attention as a PMS treatment.

OBJECTIVE

To investigate the effectiveness of Hypericum perforatum on symptoms of PMS.

STUDY DESIGN

This randomized, double-blind, placebo-controlled, crossover study was conducted between November 2005 and June 2007.

SETTING

Institute of Psychological Sciences, University of Leeds, Leeds, UK.

PARTICIPATION

36 women aged 18-45 years with regular menstrual cycles (25-35 days), who were prospectively diagnosed with mild PMS.

INTERVENTION

Women who remained eligible after three screening cycles (n = 36) underwent a two-cycle placebo run-in phase. They were then randomly assigned to receive Hypericum perforatum tablets 900 mg/day (standardized to 0.18% hypericin; 3.38% hyperforin) or identical placebo tablets for two menstrual cycles. After a placebo-treated washout cycle, the women crossed over to receive placebo or Hypericum perforatum for two additional cycles.

MAIN OUTCOME MEASURES

Symptoms were rated daily throughout the trial using the Daily Symptom Report. Secondary outcome measures were the State Anxiety Inventory, Beck Depression Inventory, Aggression Questionnaire and Barratt Impulsiveness Scale. Plasma hormone (follicle-stimulating hormone [FSH], luteinizing hormone [LH], estradiol, progesterone, prolactin and testosterone) and cytokine (interleukin [IL]-1beta, IL-6, IL-8, interferon [IFN]-gamma and tumour necrosis factor [TNF]-alpha) levels were measured in the follicular and luteal phases during Hypericum perforatum and placebo treatment.

RESULTS

Hypericum perforatum was statistically superior to placebo in improving physical and behavioural symptoms of PMS (p < 0.05). There were no significant effects of Hypericum perforatum compared with placebo treatment for mood- and pain-related PMS symptoms (p > 0.05). Plasma hormone (FSH, LH, estradiol, progesterone, prolactin and testosterone) and cytokine (IL-1beta, IL-6, IL-8, IFNgamma and TNFalpha) levels, and weekly reports of anxiety, depression, aggression and impulsivity, also did not differ significantly during the Hypericum perforatum and placebo cycles (p > 0.05).

CONCLUSION

Daily treatment with Hypericum perforatum was more effective than placebo treatment for the most common physical and behavioural symptoms associated with PMS. As proinflammatory cytokine levels did not differ significantly between Hypericum perforatum and placebo treatment, these beneficial effects are unlikely to be produced through this mechanism of action alone. Further work is needed to determine whether pain- and mood-related PMS symptoms benefit from longer treatment duration. Trial registration number (International Standard Randomised Controlled Trial Number Register) ISRCTN31487459.

How (and why) the immune system makes us sleep

Good sleep is necessary for physical and mental health. For example, sleep loss impairs immune function, and sleep is altered during infection. Immune signalling molecules are present in the healthy brain, where they interact with neurochemical systems to contribute to the regulation of normal sleep. Animal studies have shown that interactions between immune signalling molecules (such as the cytokine interleukin 1) and brain neurochemical systems (such as the serotonin system) are amplified during infection, indicating that these interactions might underlie the changes in sleep that occur during infection. Why should the immune system cause us to sleep differently when we are sick? We propose that the alterations in sleep architecture during infection are exquisitely tailored to support the generation of fever, which in turn imparts survival value.

Effects of serotonergic activation by 5-hydroxytryptophan on sleep and body temperature of C57BL/6J and interleukin-6-deficient mice are dose and time related

STUDY OBJECTIVES

Extensive data implicate serotonin (5-hydroxytryptamine [5-HT]) in the regulation of sleep. Jouvet has hypothesized that 5-HT promotes wakefulness, yet is necessary for subsequent non-rapid eye movement (NREM) sleep, actions he proposes to be mediated by sleep factors. Studies in rat support this dual role for 5-HT. The objectives of this study were to (1) determine effects of serotonergic activation on sleep of mice and (2) elucidate a potential role for the cytokine interleukin-6 as a sleep factor mediating serotonergic effects on sleep.

DESIGN

C57BL/6J and B6.129S6-II6(tm1Kopf)(interleukin-6 knockout [IL-6 KO]) mice were purchased from the Jackson Laboratory and instrumented for recording the electroencephalogram and body temperature. After recovery, separate groups of mice were injected intraperitoneally at either light or dark onset with vehicle or with the 5-HT precursor 5-hydroxytryptophan (5-HTP). Sleep-wake behavior was determined and body temperature recorded for 24 hours after injections.

RESULTS

5-HTP induced hypothermia in both mouse strains. When injected at dark onset, the highest dose of 5-HTP (200 mg/kg) increased NREM sleep. Light onset administration initially increased wakefulness, with increases in NREM sleep apparent only during the subsequent dark period. For most parameters, there were no differences in responses between strains. However IL-6 KO mice at some doses exhibited a greater increase in NREM sleep.

CONCLUSIONS

5-HTP alters sleep-wake behavior and body temperature of mice in a manner similar to that of rats. Increases in NREM sleep after 5-HTP are apparent only during the dark period, which may represent a fundamental property of the serotonergic system. These results suggest that 5-HT should not be considered either wake promoting or NREM sleep promoting. Rather, the role of 5-HT in the regulation of sleep-wake behavior must be considered within the context of the degree to which the system is activated and the time at which the activation occurs.

Role of IL-1 beta and 5-HT2 receptors in midbrain periaqueductal gray (PAG) in potentiating defensive rage behavior in cat

Feline defensive rage, a form of aggressive behavior that occurs in response to a threat can be elicited by electrical stimulation of the medial hypothalamus or midbrain periaqueductal gray (PAG). Our laboratory has recently begun a systematic examination of the role of cytokines in the regulation of rage and aggressive behavior. It was shown that the cytokine, interleukin-2 (IL-2), differentially modulates defensive rage when microinjected into the medial hypothalamus and PAG by acting through separate neurotransmitter systems. The present study sought to determine whether a similar relationship exists with respect to interleukin 1-beta (IL-1 beta), whose receptor activation in the medial hypothalamus potentiates defensive rage. Thus, the present study identified the effects of administration of IL-1 beta into the PAG upon defensive rage elicited from the medial hypothalamus. Microinjections of IL-1 beta into the dorsal PAG significantly facilitated defensive rage behavior elicited from the medial hypothalamus in a dose and time dependent manner. In addition, the facilitative effects of IL-1 beta were blocked by pre-treatment with anti-IL-1 beta receptor antibody, while IL-1 beta administration into the PAG had no effect upon predatory attack elicited from the lateral hypothalamus. The findings further demonstrated that IL-1 beta's effects were mediated through 5-HT(2) receptors since pretreatment with a 5-HT(2C) receptors antagonist blocked the facilitating effects of IL-1 beta. An extensive pattern of labeling of IL-1 beta and 5-HT(2C) receptors in the dorsal PAG supported these findings. The present study demonstrates that IL-beta in the dorsal PAG, similar to the medial hypothalamus, potentiates defensive rage behavior and is mediated through a 5-HT(2C) receptor mechanism.

Cytokines and sleep

Personal experience and empirical data indicate sleep is altered during sickness. Important signaling molecules of the peripheral immune system called cytokines orchestrate responses to infection. Through a variety of mechanisms, the brain detects activation of the peripheral immune system. The brain responds to infection by altering physiological processes and complex behavior, including sleep. These changes in physiology and behavior collectively function to support the immune system, and under normal circumstances the health of the host is restored. Several of these cytokines, and their receptors, are present in normal healthy brain. Some cytokines regulate sleep under physiological conditions, in the absence of infection or immune challenge. For example, interleukin-1 directly alters discharge patterns of neurons in hypothalamic and brainstem circuits implicated in the regulation of sleep-wake behavior. Many other cytokines modulate sleep because they interact with neurotransmitter, peptide, and/or hormone systems to initiate a cascade of responses that subsequently alter sleep-wake behavior. Because cytokines regulate/modulate sleep-wake behavior in the absence of immune challenge, and cytokine concentrations and profiles are altered during infection, it is likely that cytokines mediate infection-induced alterations in sleep. Whether the changes in sleep that occur during infection are beneficial and aid in recovery remains to be determined.

Potentiating role of interleukin-1beta (IL-1beta) and IL-1beta type 1 receptors in the medial hypothalamus in defensive rage behavior in the cat

Recently, this laboratory provided evidence that interleukin-1beta (IL-1beta), an immune and brain-derived cytokine, microinjected into the medial hypothalamus, potentiates defensive rage behavior in the cat elicited from the midbrain periaqueductal gray (PAG), and that such effects are blocked by a 5-HT2 receptor antagonist. Since this finding represents the first time that a brain cytokine has been shown to affect defensive rage behavior, the present study replicated and extended these findings by documenting the specific potentiating role played by IL-1beta Type 1 receptor (IL-1RI), and the anatomical relationship between IL-1beta and 5-HT2 receptors in the medial hypothalamus. IL-1beta (10 ng) microinjected into the medial hypothalamus induced two separate phases of facilitation, one at 60 min and another at 180 min, post-injection. In turn, these effects were blocked with pretreatment of the selective IL-1 Type I receptor antagonist (IL-1ra) (10 ng), demonstrating the selectivity of the effects of IL-1beta on medial hypothalamic neurons upon PAG-elicited defensive rage behavior. The next stage of the study utilized immunohistochemical methods to demonstrate that IL-1beta and 5-HT2 receptors were present on the same neurons within regions of the medial hypothalamus where IL-1beta and the IL-1beta receptor antagonists were administered. This provided anatomical evidence suggesting a relationship between IL-1RI and 5-HT2 receptors in the medial hypothalamus that is consistent with the previous pharmacological observations in our laboratory. The overall findings show that activation of IL-1RI in the medial hypothalamus potentiates defensive rage behavior in the cat and that these effects may also be linked to the presence of 5-HT2 receptors on the same groups of neurons in this region of hypothalamus.

Behavioral and neurochemical responses in mice bearing tumors submitted to social stress

Through the proinflammatory cytokines secreted in response to inflammation or injury, the immune system produces physiological and behavioral alterations. This study analyzes the effects on behavior, mononuclear proliferative response and central monoamine activity in response to the inoculation of tumor cells in mice submitted to social stress. Two groups of male OF1 mice were used, one of which was inoculated with B16 melanoma cells. Both groups were subdivided into two new groups, with one being submitted to social stress through sensory contact model with a selected aggressive subject, and the other being handled without social interaction. Subjects were exposed to social stress for a 24-h period, with three 5 min intervals of direct physical interaction, where the behavior was recorded and assessed. One hour after the stress and/or handling, they were put down and samples taken for physiological assessment. Significant behavioral changes were found in subjects with implanted tumors, mainly characterized by an increase in avoidance behavior and a decrease in immobility, defense-submission and non-social exploration behavior, coupled with an increase in the spleen mononuclear cell proliferative response. Similarly, an increase was observed in the density of dopamine(2) (D(2))-receptors in the striatum (SRT) and an increase in dopaminergic (DOPAC/DA) and serotonergic (5HIAA/5HT) turnover in the hypothalamus. The increase in the density of D(2)-receptors in the SRT coincides with the decrease in some behaviors with a predominant motor component. The results indicate significant changes in the defensive strategy used to cope with situations of intense social stress in mice bearing tumors.

Chronic psychosocial stress down-regulates central cytokines mRNA

Brain cytokines have been implicated in brain plasticity and mood alterations. We present here the first evidence of a chronic stress-induced modulation of central cytokines, in absence of experimentally induced inflammatory processes. Several brain areas were extracted from stressed and control mice and cytokines mRNA analyzed with semi-quantitative RT-PCR. Mice subjected to chronic psychosocial stress showed decreased interleukin (IL)-1beta mRNA levels in the hippocampus, decreased IL-1Receptor antagonist in the striatum and pituitary, decreased tumor necrosis factor (TNF)-alpha in the striatum and hippocampus, and decreased glucocorticoid receptor (GR) in the striatum and hippocampus compared to group housed sibling mice. An independent group of mice subjected to chronic psychosocial stress also showed increased plasma corticosterone. These findings may open new perspectives for understanding the pathophysiological basis of chronic stress-induced disorders.

Interleukin-1beta enhances non-rapid eye movement sleep when microinjected into the dorsal raphe nucleus and inhibits serotonergic neurons in vitro

Interleukin-1 (IL-1) and IL-1 receptors are constitutively expressed in normal brain. IL-1 increases non-rapid eye movements (NREM) sleep in several animal species, an effect mediated in part by interactions with the serotonergic system. The site(s) in brain at which interactions between IL-1 and the serotonergic system increase NREM sleep remain to be identified. The dorsal raphe (DRN) is the origin of the major ascending serotonergic pathways to the forebrain, and it contains IL-1 receptors. This study examined the hypothesis that IL-1 increases NREM sleep by acting at the level of the DRN. IL-1beta (0.25 and 0.5 ng) was microinjected into the DRN of freely behaving rats and subsequent effects on sleep-wake activity were determined. IL-1beta 0.5 ng increased NREM sleep during the first 2 h post-injection from 33.5 +/- 3.7% after vehicle microinjection to 42.9 +/- 3.0% of recording time. To determine the effects of IL-1beta on electrophysiological properties of DRN serotonergic neurons, intracellular recordings were performed in a guinea-pig brain stem slice preparation. In 26 of 32 physiologically and pharmacologically identified serotonergic neurons, IL-1beta superfusion (25 ng/mL) decreased spontaneous firing rates by 50%, from 1.6 +/- 0.2 Hz (before IL-1beta superfusion) to 0.8 +/- 0.2 Hz. This effect was reversible upon washout. These results show that IL-1beta increases NREM sleep when administered directly into the DRN. Serotonin enhances wakefulness and these novel data also suggest that IL-1beta-induced enhancement of NREM sleep could be due in part to the inhibition of DRN serotonergic neurons.