Granulocyte-macrophage colony-stimulating factor modulates rapid eye movement (REM) sleep and non-REM sleep in rats

Colony stimulating factors in the nervous system

Although traditionally seen as regulators of hematopoiesis, colony-stimulating factors (CSFs) have emerged as important players in the nervous system, both in health and disease. This review summarizes the cellular sources, patterns of expression and physiological roles of the macrophage (CSF-1, IL-34), granulocyte-macrophage (GM-CSF) and granulocyte (G-CSF) colony stimulating factors within the nervous system, with a particular focus on their actions on microglia. CSF-1 and IL-34, via the CSF-1R, are required for the development, proliferation and maintenance of essentially all CNS microglia in a temporal and regional specific manner. In contrast, in steady state, GM-CSF and G-CSF are mainly involved in regulation of microglial function. The alterations in expression of these growth factors and their receptors, that have been reported in several neurological diseases, are described and the outcomes of their therapeutic targeting in mouse models and humans are discussed.

Relationships Between a Range of Inflammatory Biomarkers and Subjective Sleep Quality in Chronic Insomnia Patients: A Clinical Study

PURPOSE

To examine whether associations exist between chronic insomnia disorder (CID) and overlooked inflammatory factors (Serum amyloid protein A [SAA]), tumor necrosis factor [TNF]-α, granulocyte-macrophage colony-stimulating factor [GM-CSF], and regulated on activation and normal T cell expressed and presumably secreted [RANTES]).

PATIENTS AND METHODS

A total of 65 CID patients and 39 sex- and age-matched good sleeper (GS) controls participated in this study. They completed a baseline survey to collect data on demographics, and were elevated sleep and mood by Pittsburgh Sleep Quality Index (PSQI), Athens Insomnia Scale (AIS), 17-item Hamilton Depression Rating Scale (HAMD-17) and 14-item Hamilton Anxiety Rating Scale (HAMA-14), respectively. The blood samples were collected and tested the serum levels of SAA, TNF-α, GM-CSF and RANTES.

RESULTS

The CID group had higher serum levels of SAA, TNF-α, and GM-CSF and a lower level of RANTES than the GS group. In the Spearman correlation analysis, SAA and GM-CSF positively correlated with the PSQI and AIS scores. After controlling for sex, HAMD-17 score, and HAMA-14 score, the partial correlation analysis showed that GM-CSF was positively correlated with PSQI score. Further stepwise linear regression analyses showed that GM-CSF was positively associated with the PSQI and AIS scores, while RANTES was negatively associated with them, and SAA was positively associated with just the AIS score.

CONCLUSION

The serum levels of inflammatory mediators (SAA, TNF-α, and GM-CSF) were significantly elevated and the level of RANTES was significantly decreased in CID patients and, to some extent, the changes are related to the severity of insomnia. These findings may help us to improve interventions to prevent the biological consequences of CID by inhibiting inflammation, thereby promoting health.

The Effects of Frankincense Essential Oil on Stress in Rats

Frankincense essential oil, obtained from Boswellia carteri, is a popular essential oil, which is widely used in many parts of the world. While some of its properties are known, its effects on stress and sleep have not been studied. The effects of frankincense essential oil and its major components, limonene and α-pinene, on plasma corticosterone and glutathione (GSH) levels, as well as on sleep and wakefulness behaviour, were studied in sleep-deprived rats. The substances were applied topically after dilution in jojoba oil (vehicle). As compared to vehicle, frankincense essential oil at a dilution of 1/1000 (1:10³) significantly reduced corticosterone levels (p < 0.05). In contrast, its major constituents (α-pinene and limonene), elevated levels of this stress hormone. Frankincense, limonene and α-pinene, all led to significant reductions in plasma GSH levels. Although frankincense dose-dependently reduced plasma concentrations of antioxidant ions albeit to levels insufficient to neutralize oxidative stress; levels of products of oxidative metabolism metabolites were decreased by the frankincense. In sleep-deprived rats, frankincense 1:10³ respectively increased and decreased the amount of wakefulness and non-rapid eye movement sleep. Frankincense essential oil can counter the effects of stress by effectively relieving sleep debt and maintaining antioxidant capacity without increasing oxidative stress, and, therefore, may be beneficial in the management of stress.

Minocycline alleviates behavioral deficits and inhibits microglial activation induced by intrahippocampal administration of Granulocyte-Macrophage Colony-Stimulating Factor in adult rats

Some evidence has shown an increased number of activated microglial cells in patients with schizophrenia. It is hypothesized that activated microglia may contribute to the pathogenesis of schizophrenia. We injected saline or Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) into the ventral hippocampus in adult Sprague-Dawley rats via micro-pump; at the same time, the rats were intragastrically administrated with saline or minocycline once a day for 14 consecutive days. Then, behavioral tests were examined and microglia were assessed using immunohistochemistry method. GM-CSF-injected group showed significant behavioral deficits (hyperlocomotion, social interaction deficits, prepulse inhibition (PPI) deficits). There was a dramatic increase of the number of activated microglial cells in the hippocampus and other brain regions such as cerebral cortex and thalamus compared with those in saline-injected group in immunohistochemistry. Minocycline was able to ameliorate deficits of social interaction and PPI but not hyperlocomotion. Minocycline was also able to inhibit the microglial activation. In conclusion, intrahippocampal administration of GM-CSF in adult rats may serve as a potential schizophrenia animal model, which may be related with the microglia hypothesis of schizophrenia.

Daily exercise improves memory, stimulates hippocampal neurogenesis and modulates immune and neuroimmune cytokines in aging rats

We tested whether daily exercise modulates immune and neuroimmune cytokines, hippocampus-dependent behavior and hippocampal neurogenesis in aging male F344 rats (18mo upon arrival). Twelve weeks after conditioned running or control group assignment, the rats were trained and tested in a rapid water maze followed by an inhibitory avoidance task. The rats were BrdU-injected beginning 12days after behavioral testing and killed 3weeks later to quantify cytokines and neurogenesis. Daily exercise increased neurogenesis and improved immediate and 24h water maze discrimination index (DI) scores and 24h inhibitory avoidance retention latencies. Daily exercise decreased cortical VEGF, hippocampal IL-1β and serum MCP-1, GRO-KC and leptin levels but increased hippocampal GRO-KC and IL-18 concentrations. Serum leptin concentration correlated negatively with new neuron number and both DI scores while hippocampal IL-1β concentration correlated negatively with memory scores in both tasks. Cortical VEGF, serum GRO-KC and serum MCP-1 levels correlated negatively with immediate DI score and we found novel positive correlations between hippocampal IL-18 and GRO-KC levels and new neuron number. Pathway analyses revealed distinct serum, hippocampal and cortical compartment cytokine relationships. Our results suggest that daily exercise potentially improves cognition in aging rats by modulating hippocampal neurogenesis and immune and neuroimmune cytokine signaling. Our correlational data begin to provide a framework for systematically manipulating these immune and neuroimmune signaling molecules to test their effects on cognition and neurogenesis across lifespan in future experiments.

Spontaneous sleep in mice with targeted disruptions of neuronal or inducible nitric oxide synthase genes

Nitric oxide (NO) affects almost every physiological process, including the regulation of sleep. There is strong evidence that NO plays an important role in rapid eye movement sleep (REMS) regulation. To further investigate the role of NO in sleep, we characterized spontaneous sleep in mice with targeted disruptions (knockout; KO) in the neuronal nitric oxide synthase (nNOS) or inducible (i)NOS genes. REMS in nNOS KO mice was substantially lower than that of their control mice. In contrast, the iNOS KO mice had significantly more REMS than their controls. Inducible NOS KO mice also had less non-REMS (NREMS) during the dark period. Results suggest that nNOS and iNOS play opposite roles in REMS regulation.

Cytokines and cognition--the case for a head-to-toe inflammatory paradigm

The brain is not only immunologically active of its own accord, but also has complex peripheral immune interactions. Given the central role of cytokines in neuroimmmunoendocrine processes, it is hypothesized that these molecules influence cognition via diverse mechanisms. Peripheral cytokines penetrate the blood-brain barrier directly via active transport mechanisms or indirectly via vagal nerve stimulation. Peripheral administration of certain cytokines as biological response modifiers produces adverse cognitive effects in animals and humans. There is abundant evidence that inflammatory mechanisms within the central nervous system (CNS) contribute to cognitive impairment via cytokine-mediated interactions between neurons and glial cells. Cytokines mediate cellular mechanisms subserving cognition (e.g., cholinergic and dopaminergic pathways) and can modulate neuronal and glial cell function to facilitate neuronal regeneration or neurodegeneration. As such, there is a growing appreciation of the role of cytokine-mediated inflammatory processes in neurodegenerative diseases such as Alzheimer's disease and vascular dementia. Consistent with their involvement as mediators of bidirectional communication between the CNS and the peripheral immune system, cytokines play a key role in the hypothalamic-pituitary-adrenal axis activation seen in stress and depression. In addition, complex cognitive systems such as those that underlie religious beliefs, can modulate the effects of stress on the immune system. Indirect means by which peripheral or central cytokine dysregulation could affect cognition include impaired sleep regulation, micronutrient deficiency induced by appetite suppression, and an array of endocrine interactions. Given the multiple levels at which cytokines are capable of influencing cognition it is plausible that peripheral cytokine dysregulation with advancing age interacts with cognitive aging.

Arousal effects of orexin-A correlate with GLU release from the locus coeruleus in rats

Although orexin was found to promote food intake, recent reports proposed its involvement in the regulation of vigilance. To study the mechanism of how orexin affects arousal, we analyzed glutamate (GLU) release from the locus coeruleus (LC) in rats after systemic injection of orexin-A. Baseline levels of orexin-A in the LC were significantly higher during the dark period than the light period. Intravenous administration of orexin-A increased GLU levels as well as orexin in the LC, simultaneously promoting wakefulness. These results suggest that increases in GLU release may reflect the arousal-inducing effects of orexin.

Involvement of granulocyte-macrophage colony-stimulating factor (GM-CSF) in pregnancy-enhanced sleep

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a crucial cytokine for establishing pregnancy. It has been demonstrated previously in rats that sleep increases during early pregnancy and that centrally administered GM-CSF promotes both rapid eye movement (REM) and non-REM sleep. Therefore, whether GM-CSF is involved in pregnancy-enhanced sleep was investigated using the anti-GM-CSF antibody. Female rats received an intracerebroventricular infusion of either anti-GM-CSF or control IgG (10 microg each) for four nights from the first day of pregnancy (PD1-PD4). Although sleep amounts on PD1 were not affected, anti-GM-CSF decreased non-REM and REM sleep significantly during PD2-PD4 compared with the control baseline of the IgG group. The results demonstrated that anti-GM-CSF treatment suppresses pregnancy-enhanced sleep, suggesting that GM-CSF contributes to sleep regulation during pregnancy.

The sulphydryl reagent, N-ethylmaleimide, disrupts sleep and blocks A1 adenosine receptor-mediated inhibition of intracellular calcium signaling in the in vitro ventromedial preoptic nucleus

To explore the neuronal signaling mechanisms underlying sleep regulation in the rat, the present study examined continuous intra-third ventricle infusion of N-ethylmaleimide (NEM), a sulphydryl reagent that inhibits G(i/o) protein-coupled receptor-mediated signaling pathways. The diurnal infusion of NEM (0.01-10 micromol/10 h) dose-dependently inhibited both non-rapid eye movement sleep and rapid eye movement sleep. A maximal dose of NEM (10 micromol/10 h) dramatically inhibited day-time sleep (-57% for non-rapid eye movement sleep and -89% for rapid eye movement sleep) with a compensatory increase of sleep during the subsequent night-time (+33% for non-rapid eye movement sleep and +259% for rapid eye movement sleep). The day-time brain temperature was also increased by NEM, demonstrating effects of NEM on both sleep and body temperature levels. Immunostaining of the rat hypothalamus with a monoclonal antibody against the A1 adenosine receptor (A1R) was used to explore the distribution of a sleep-related G(i/o) protein-coupled receptor. Robust A1R-like immunoreactivity was found in the ventromedial preoptic nucleus and the supraoptic nucleus. Fura-2-based Ca(2+) imaging analysis of acute hypothalamic slices further demonstrated that the A1R agonist N(6)-cyclopentyladenosine (CPA; 200 nM) inhibited spontaneous Ca(2+) oscillations and high potassium (80 mM)-induced Ca(2+) flux in the ventromedial preoptic nucleus, while NEM (100-300 microM) and an A1R antagonist 8-cyclopentyl-dipropylxanthine (300 nM) blocked the CPA actions and increased the high potassium-induced Ca(2+) flux. From these results we suggest that NEM-sensitive G protein-coupled receptor(s) may play an important role in the regulation of sleep and body temperature in the rat and one possible mechanism is an A1R-mediated regulation of intracellular Ca(2+) concentrations in the ventromedial preoptic nucleus.

Sleep-promoting activity of prolactin-releasing peptide (PrRP) in the rat

The present study examines whether or not prolactin-releasing peptide (PrRP) infused intracerebroventricularly (i.c.v.) affects sleep and the release of prolactin (PRL) and growth hormone (GH) in rats. At a dose of 0.1 nmol, PrRP promoted rapid-eye-movement (REM) sleep, whereas 1.0 nmol increased both non-REM and REM sleep and 10.0 nmol enhanced only non-REM sleep. During the i.c.v. infusion of PrRP with 0.1 nmol, levels of plasma PRL were elevated, but GH levels were significantly decreased. Since it is reported that PrRP fails to induce PRL release from the male pituitary, the stimulatory effects of PrRP on PRL release observed here seem to be indirect. However, PRL stimulated by i.c.v.-infused PrRP could take part in the REM sleep-promoting activity of PrRP.