Central administration of transforming growth factor-alpha and neuregulin-1 suppress active behaviors and cause weight loss in hamsters

Sleep drive is coupled to tissue damage via shedding of Caenorhabditis elegans EGFR ligand SISS-1

The benefits of sleep extend beyond the nervous system. Peripheral tissues impact sleep regulation, and increased sleep is observed in response to damaging conditions, even those that selectively affect non-neuronal cells. However, the 'sleep need' signal released by stressed tissues is not known. Sleep in the nematode C. elegans is independent of circadian cues and can be triggered rapidly by damaging conditions. This stress-induced sleep is mediated by neurons that require the Epidermal Growth Factor Receptor (EGFR) for their sleep-promoting function, but the only known C. elegans EGFR ligand, LIN-3, is not required for sleep. Here we describe SISS-1 (stress-induced sleepless), an EGF family ligand that is required for stress-induced sleep. We show that SISS-1 overexpression induces sleep in an EGFR-dependent, sleep neuron-dependent manner. We find that SISS-1 undergoes stress-responsive shedding by the ADM-4/ADAM17 metalloprotease, and that the ADM-4 site of action depends on the tissue specificity of the stressor. Our findings support a model in which SISS-1 is released from damaged tissues to activate EGFR in sleep neurons, identifying a molecular link between cellular stress and organismal sleep drive. Our data also point to a mechanism insulating this sleep signal from EGFR-mediated signaling during development.

Energy Expenditure Homeostasis Requires ErbB4, an Obesity Risk Gene, in the Paraventricular Nucleus

Obesity affects more than a third adult population in the United States; the prevalence is even higher in patients with major depression disorders. GWAS studies identify the receptor tyrosine kinase ErbB4 as a risk gene for obesity and for major depression disorders. We found that ErbB4 was enriched in the paraventricular nucleus of the hypothalamus (PVH). To investigate its role in metabolism, we deleted ErbB4 by injecting a Cre-expressing virus into the PVH of ErbB4-floxed male mice and found that PVH ErbB4 deletion increased weight gain without altering food intake. ErbB4 PVH deletion also reduced nighttime activity and decreased intrascapular brown adipose tissue (iBAT) thermogenesis. Analysis of covariance (ANCOVA) revealed that ErbB4 PVH deletion reduced O2 consumption, CO2 production and heat generation in a manner independent of body weight. Immunostaining experiments show that ErbB4+ neurons in the PVH were positive for oxytocin (OXT); ErbB4 PVH deletion reduces serum levels of OXT. We characterized mice where ErbB4 was specifically mutated in OXT+ neurons and found reduction in energy expenditure, phenotypes similar to PVH ErbB4 deletion. Taken together, our data indicate that ErbB4 in the PVH regulates metabolism likely through regulation of OXT expressing neurons, reveal a novel function of ErbB4 and provide insight into pathophysiological mechanisms of depression-associated obesity.

Does EGFR Signaling Mediate Orexin System Activity in Sleep Initiation?

Sleep-wake cycle disorders are an important symptom of many neurological diseases, including Parkinson's disease, Alzheimer's disease, and multiple sclerosis. Circadian rhythms and sleep-wake cycles play a key role in maintaining the health of organisms. To date, these processes are still poorly understood and, therefore, need more detailed elucidation. The sleep process has been extensively studied in vertebrates, such as mammals and, to a lesser extent, in invertebrates. A complex, multi-step interaction of homeostatic processes and neurotransmitters provides the sleep-wake cycle. Many other regulatory molecules are also involved in the cycle regulation, but their functions remain largely unclear. One of these signaling systems is epidermal growth factor receptor (EGFR), which regulates the activity of neurons in the modulation of the sleep-wake cycle in vertebrates. We have evaluated the possible role of the EGFR signaling pathway in the molecular regulation of sleep. Understanding the molecular mechanisms that underlie sleep-wake regulation will provide critical insight into the fundamental regulatory functions of the brain. New findings of sleep-regulatory pathways may provide new drug targets and approaches for the treatment of sleep-related diseases.

PET-CT and RNA sequencing reveal novel targets for acupuncture-induced lowering of blood pressure in spontaneously hypertensive rats

Manual acupuncture (MA) can be used to manage high blood pressure; however, the underlying molecular mechanism remains unknown. To explore the mechanism of acupuncture in the treatment of hypertension, Wistar Kyoto rats (WKYs) and spontaneously hypertensive rats (SHRs) were subjected to either MA stimulation or the corresponding sham procedure as a negative control (Sham-MA) for 1 week. PET-CT scans, transcriptomics and molecular biology were used to evaluate the effect of MA. The results show that MA can regulate blood pressure in SHRs, change the glucose metabolism of the paraventricular hypothalamus (PVH), and affect the mRNA and protein expression levels of differentially expressed genes in the PVH. These genes may lower blood pressure by regulating angiotensin, endothelial function and inflammation. These findings reveal that MA regulates multiple biological processes and genes/proteins of the PVH, and provide a solid theoretical basis for exploring the mechanisms by which MA regulates hypertension.

Epigenetic Regulation of Neuregulin-1 Tunes White Adipose Stem Cell Differentiation

Expansion of subcutaneous adipose tissue by differentiation of new adipocytes has been linked to improvements in metabolic health. However, an expandability limit has been observed wherein new adipocytes cannot be produced, the existing adipocytes become enlarged (hypertrophic) and lipids spill over into ectopic sites. Inappropriate ectopic storage of these surplus lipids in liver, muscle, and visceral depots has been linked with metabolic dysfunction. Here we show that Neuregulin-1 (NRG1) serves as a regulator of adipogenic differentiation in subcutaneous primary human stem cells. We further demonstrate that DNA methylation modulates NRG1 expression in these cells, and a 3-day exposure of stem cells to a recombinant NRG1 peptide fragment is sufficient to reprogram adipogenic cellular differentiation to higher levels. These results define a novel molecular adipogenic rheostat with potential implications for the expansion of adipose tissue in vivo.

Epidermal Growth Factor Signaling Promotes Sleep through a Combined Series and Parallel Neural Circuit

Sleep requires sleep-active neurons that depolarize to inhibit wake circuits. Sleep-active neurons are under the control of homeostatic mechanisms that determine sleep need. However, little is known about the molecular and circuit mechanisms that translate sleep need into the depolarization of sleep-active neurons. During many stages and conditions in C. elegans, sleep requires a sleep-active neuron called RIS. Here, we defined the transcriptome of RIS and discovered that genes of the epidermal growth factor receptor (EGFR) signaling pathway are expressed in RIS. Because of cellular stress, EGFR directly activates RIS. Activation of EGFR signaling in the ALA neuron has previously been suggested to promote sleep independently of RIS. Unexpectedly, we found that ALA activation promotes RIS depolarization. Our results suggest that ALA is a drowsiness neuron with two separable functions: (1) it inhibits specific behaviors, such as feeding, independently of RIS, (2) and it activates RIS. Whereas ALA plays a strong role in surviving cellular stress, surprisingly, RIS does not. In summary, EGFR signaling can depolarize RIS by an indirect mechanism through activation of the ALA neuron that acts upstream of the sleep-active RIS neuron and through a direct mechanism using EGFR signaling in RIS. ALA-dependent drowsiness, rather than RIS-dependent sleep bouts, appears to be important for increasing survival after cellular stress, suggesting that different types of behavioral inhibition play different roles in restoring health. VIDEO ABSTRACT.

Evolutionarily conserved regulation of sleep by epidermal growth factor receptor signaling

The genetic bases for most human sleep disorders and for variation in human sleep quantity and quality are largely unknown. Using the zebrafish, a diurnal vertebrate, to investigate the genetic regulation of sleep, we found that epidermal growth factor receptor (EGFR) signaling is necessary and sufficient for normal sleep levels and is required for the normal homeostatic response to sleep deprivation. We observed that EGFR signaling promotes sleep via mitogen-activated protein kinase/extracellular signal-regulated kinase and RFamide neuropeptide signaling and that it regulates RFamide neuropeptide expression and neuronal activity. Consistent with these findings, analysis of a large cohort of human genetic data from participants of European ancestry revealed that common variants in genes within the EGFR signaling pathway are associated with variation in human sleep quantity and quality. These results indicate that EGFR signaling and its downstream pathways play a central and ancient role in regulating sleep and provide new therapeutic targets for sleep disorders.

Systems Chronotherapeutics

Chronotherapeutics aim at treating illnesses according to the endogenous biologic rhythms, which moderate xenobiotic metabolism and cellular drug response. The molecular clocks present in individual cells involve approximately fifteen clock genes interconnected in regulatory feedback loops. They are coordinated by the suprachiasmatic nuclei, a hypothalamic pacemaker, which also adjusts the circadian rhythms to environmental cycles. As a result, many mechanisms of diseases and drug effects are controlled by the circadian timing system. Thus, the tolerability of nearly 500 medications varies by up to fivefold according to circadian scheduling, both in experimental models and/or patients. Moreover, treatment itself disrupted, maintained, or improved the circadian timing system as a function of drug timing. Improved patient outcomes on circadian-based treatments (chronotherapy) have been demonstrated in randomized clinical trials, especially for cancer and inflammatory diseases. However, recent technological advances have highlighted large interpatient differences in circadian functions resulting in significant variability in chronotherapy response. Such findings advocate for the advancement of personalized chronotherapeutics through interdisciplinary systems approaches. Thus, the combination of mathematical, statistical, technological, experimental, and clinical expertise is now shaping the development of dedicated devices and diagnostic and delivery algorithms enabling treatment individualization. In particular, multiscale systems chronopharmacology approaches currently combine mathematical modeling based on cellular and whole-body physiology to preclinical and clinical investigations toward the design of patient-tailored chronotherapies. We review recent systems research works aiming to the individualization of disease treatment, with emphasis on both cancer management and circadian timing system–resetting strategies for improving chronic disease control and patient outcomes.

Interaction between prenatal pesticide exposure and a common polymorphism in the PON1 gene on DNA methylation in genes associated with cardio-metabolic disease risk-an exploratory study

BACKGROUND

Prenatal environmental conditions may influence disease risk in later life. We previously found a gene-environment interaction between the paraoxonase 1 (PON1) Q192R genotype and prenatal pesticide exposure leading to an adverse cardio-metabolic risk profile at school age. However, the molecular mechanisms involved have not yet been resolved. It was hypothesized that epigenetics might be involved. The aim of the present study was therefore to investigate whether DNA methylation patterns in blood cells were related to prenatal pesticide exposure level, PON1 Q192R genotype, and associated metabolic effects observed in the children.

METHODS

Whole blood DNA methylation patterns in 48 children (6-11 years of age), whose mothers were occupationally unexposed or exposed to pesticides early in pregnancy, were determined by Illumina 450 K methylation arrays.

RESULTS

A specific methylation profile was observed in prenatally pesticide exposed children carrying the PON1 192R-allele. Differentially methylated genes were enriched in several neuroendocrine signaling pathways including dopamine-DARPP32 feedback (appetite, reward pathways), corticotrophin releasing hormone signaling, nNOS, neuregulin signaling, mTOR signaling, and type II diabetes mellitus signaling. Furthermore, we were able to identify possible candidate genes which mediated the associations between pesticide exposure and increased leptin level, body fat percentage, and difference in BMI Z score between birth and school age.

CONCLUSIONS

DNA methylation may be an underlying mechanism explaining an adverse cardio-metabolic health profile in children carrying the PON1 192R-allele and prenatally exposed to pesticides.

Sleep and Development in Genetically Tractable Model Organisms

Sleep is widely recognized as essential, but without a clear singular function. Inadequate sleep impairs cognition, metabolism, immune function, and many other processes. Work in genetic model systems has greatly expanded our understanding of basic sleep neurobiology as well as introduced new concepts for why we sleep. Among these is an idea with its roots in human work nearly 50 years old: sleep in early life is crucial for normal brain maturation. Nearly all known species that sleep do so more while immature, and this increased sleep coincides with a period of exuberant synaptogenesis and massive neural circuit remodeling. Adequate sleep also appears critical for normal neurodevelopmental progression. This article describes recent findings regarding molecular and circuit mechanisms of sleep, with a focus on development and the insights garnered from models amenable to detailed genetic analyses.

A mechanism for sickness sleep: lessons from invertebrates

During health, animal sleep is regulated by an internal clock and by the duration of prior wakefulness. During sickness, sleep is regulated by cytokines released from either peripheral cells or from cells within the nervous system. These cytokines regulate central nervous system neurons to induce sleep. Recent research in the invertebrates Caenorhabditis elegans and Drosophila melanogaster has led to new insights into the mechanism of sleep during sickness. Sickness is triggered by exposure to environments such as infection, heat, or ultraviolet light irradiation, all of which cause cellular stress. Epidermal growth factor is released from stressed cells and signals to activate central neuroendocrine cell(s). These neuron(s) release neuropeptides including those containing an amidated arginine(R)-phenylalanine(F) motif at their C-termini (RFamide peptides). Importantly, mechanisms regulating sickness sleep are partially distinct from those regulating healthy sleep. We will here review key findings that have elucidated the central neuroendocrine mechanism of sleep during sickness. Adaptive mechanisms employed in the control of sickness sleep may play a role in correcting cellular homeostasis after various insults. We speculate that these mechanisms may play a maladaptive role in human pathological conditions such as in the fatigue and anorexia associated with autoimmune diseases, with major depression, and with unexplained chronic fatigue.

Association of fatigue and depression with circulating levels of proinflammatory cytokines and epidermal growth factor receptor ligands: a correlative study of a placebo-controlled fatigue trial

Context

The biology of fatigue and depression in cancer patients is poorly understood. Hypotheses regarding cytokines and growth factors related to sickness behavior and disruption of circadian signaling have been proposed.

Objectives

We prospectively examined proinflammatory cytokines (e.g., sickness behavior model) and epidermal growth factor receptor (EGFR) ligands (e.g., circadian disruption model) in the serum of cancer patients enrolled in a clinical trial testing levocarnitine for fatigue.

Methods

Serum samples were collected at baseline and week 4. Cytokine/growth factor analyses were performed with a Luminex analyzer. The Brief Fatigue Index and the Center for Epidemiologic Studies Depression Index were used to measure fatigue and depression severity. The association between cytokine and symptoms was examined using logistic models.

Results

Among 101 analyzable patients, all ten cytokines/growth factors examined were highly elevated at baseline and all significantly decreased at week 4 (p<0.001) regardless of treatment intervention. At baseline, the odds of severe fatigue significantly increased for patients with higher level of interleukin-1 receptor antagonist (IL-1Ra), whereas patients with higher levels of IL-1Ra, tumor necrosis factor-α, interleukin (IL)-6, IL-8, interferon-γ, transforming growth factor α, and vascular endothelial growth factor had higher odds of severe depression. At week 4, fatigue (p=0.023) and depression (p=0.007) responders had less decrease in IL-1 level than the corresponding non-responders.

Conclusion

In this correlative analysis of a fatigue clinical trial, levels of fatigue were significantly associated with levels of IL-1 and IL-1Ra. Circadian-signaling pathways related to EGFR signaling were correlated with depression as were other cytokines. A major placebo effect was associated with a global decrease in cytokine and growth factors. These data provide further basis for testing hypotheses regarding the mechanisms of fatigue and depression in cancer patients.

C. elegans Stress-Induced Sleep Emerges from the Collective Action of Multiple Neuropeptides

The genetic basis of sleep regulation remains poorly understood. In C. elegans, cellular stress induces sleep through epidermal growth factor (EGF)-dependent activation of the EGF receptor in the ALA neuron. The downstream mechanism by which this neuron promotes sleep is unknown. Single-cell RNA sequencing of ALA reveals that the most highly expressed, ALA-enriched genes encode neuropeptides. Here we have systematically investigated the four most highly enriched neuropeptides: flp-7, nlp-8, flp-24, and flp-13. When individually removed by null mutation, these peptides had little or no effect on stress-induced sleep. However, stress-induced sleep was abolished in nlp-8; flp-24; flp-13 triple-mutant animals, indicating that these neuropeptides work collectively in controlling stress-induced sleep. We tested the effect of overexpression of these neuropeptide genes on five behaviors modulated during sleep-pharyngeal pumping, defecation, locomotion, head movement, and avoidance response to an aversive stimulus-and we found that, if individually overexpressed, each of three neuropeptides (nlp-8, flp-24, or flp-13) induced a different suite of sleep-associated behaviors. These overexpression results raise the possibility that individual components of sleep might be specified by individual neuropeptides or combinations of neuropeptides.

Expression and Function of the Epidermal Growth Factor Receptor in Physiology and Disease

The epidermal growth factor receptor (EGFR) is the prototypical member of a family of membrane-associated intrinsic tyrosine kinase receptors, the ErbB family. EGFR is activated by multiple ligands, including EGF, transforming growth factor (TGF)-α, HB-EGF, betacellulin, amphiregulin, epiregulin, and epigen. EGFR is expressed in multiple organs and plays important roles in proliferation, survival, and differentiation in both development and normal physiology, as well as in pathophysiological conditions. In addition, EGFR transactivation underlies some important biologic consequences in response to many G protein-coupled receptor (GPCR) agonists. Aberrant EGFR activation is a significant factor in development and progression of multiple cancers, which has led to development of mechanism-based therapies with specific receptor antibodies and tyrosine kinase inhibitors. This review highlights the current knowledge about mechanisms and roles of EGFR in physiology and disease.

A Conserved GEF for Rho-Family GTPases Acts in an EGF Signaling Pathway to Promote Sleep-like Quiescence in Caenorhabditis elegans

Sleep is evolutionarily conserved and required for organism homeostasis and survival. Despite this importance, the molecular and cellular mechanisms underlying sleep are not well understood. Caenorhabditis elegans exhibits sleep-like behavioral quiescence and thus provides a valuable, simple model system for the study of cellular and molecular regulators of this process. In C. elegans, epidermal growth factor receptor (EGFR) signaling is required in the neurosecretory neuron ALA to promote sleep-like behavioral quiescence after cellular stress. We describe a novel role for VAV-1, a conserved guanine nucleotide exchange factor (GEF) for Rho-family GTPases, in regulation of sleep-like behavioral quiescence. VAV-1, in a GEF-dependent manner, acts in ALA to suppress locomotion and feeding during sleep-like behavioral quiescence in response to cellular stress. Additionally, VAV-1 activity is required for EGF-induced sleep-like quiescence and normal levels of EGFR and secretory dense core vesicles in ALA. Importantly, the role of VAV-1 in promoting cellular stress-induced behavioral quiescence is vital for organism health because VAV-1 is required for normal survival after cellular stress.

Neuropeptidergic control of sleep and wakefulness

Sleep and wake are fundamental behavioral states whose molecular regulation remains mysterious. Brain states and body functions change dramatically between sleep and wake, are regulated by circadian and homeostatic processes, and depend on the nutritional and emotional condition of the animal. Sleep-wake transitions require the coordination of several brain regions and engage multiple neurochemical systems, including neuropeptides. Neuropeptides serve two main functions in sleep-wake regulation. First, they represent physiological states such as energy level or stress in response to environmental and internal stimuli. Second, neuropeptides excite or inhibit their target neurons to induce, stabilize, or switch between sleep-wake states. Thus, neuropeptides integrate physiological subsystems such as circadian time, previous neuron usage, energy homeostasis, and stress and growth status to generate appropriate sleep-wake behaviors. We review the roles of more than 20 neuropeptides in sleep and wake to lay the foundation for future studies uncovering the mechanisms that underlie the initiation, maintenance, and exit of sleep and wake states.

Neuregulin 1 Prevents Phencyclidine-Induced Behavioral Impairments and Disruptions to GABAergic Signaling in Mice

BACKGROUND

Substantial evidence from human post-mortem and genetic studies has linked the neurotrophic factor neuregulin 1 (NRG1) to the pathophysiology of schizophrenia. Genetic animal models and in vitro experiments have suggested that altered NRG1 signaling, rather than protein changes, contributes to the symptomatology of schizophrenia. However, little is known about the effect of NRG1 on schizophrenia-relevant behavior and neurotransmission (particularly GABAergic and glutamatergic) in adult animals.

METHOD

To address this question, we treated adult mice with the extracellular signaling domain of NRG1 and assessed spontaneous locomotor activity and acoustic startle response, as well as extracellular GABA, glutamate, and glycine levels in the prefrontal cortex and hippocampus via microdialysis. Furthermore, we asked whether the effect of NRG1 would differ under schizophrenia-relevant impairments in mice and therefore co-treated mice with NRG1 and phencyclidine (PCP) (3 mg/kg).

RESULTS

Acute intraventricularly- or systemically-injected NRG1 did not affect spontaneous behavior, but prevented PCP induced hyperlocomotion and deficits of prepulse inhibition. NRG1 retrodialysis (10 nM) reduced extracellular glutamate and glycine levels in the prefrontal cortex and hippocampus, and prevented PCP-induced increase in extracellular GABA levels in the hippocampus.

CONCLUSION

With these results, we provide the first compelling in vivo evidence for the involvement of NRG1 signaling in schizophrenia-relevant behavior and neurotransmission in the adult nervous system, which highlight its treatment potential. Furthermore, the ability of NRG1 treatment to alter GABA, glutamate, and glycine levels in the presence of PCP also suggests that NRG1 signaling has the potential to alter disrupted neurotransmission in patients with schizophrenia.

GGF2 is neuroprotective in a rat model of cavernous nerve injury-induced erectile dysfunction

INTRODUCTION

Erectile dysfunction is a major complication of radical prostatectomy, commonly associated with penile neuropathy. In animal models of peripheral nerve injury, glial growth factor-2 (GGF2), a member of the neuregulin family of growth factors, has neuroprotective and neurorestorative properties, but this potential has not been established after cavernous nerve (CN) injury.

AIMS

The effectiveness of GGF2 in preserving axonal integrity and recovering erectile function in a rat model of radical prostatectomy-associated CN injury.

METHODS

Adult male Sprague-Dawley rats underwent bilateral CN crush injury (BCNI) or sham surgery. Rats were administered GGF2 (0.5, 5, or 15 mg/kg) or vehicle subcutaneously 24 hour pre and 24-hour post-BCNI, and once weekly for 5 weeks. Erectile function was assessed in response to electrical stimulation of the CN. CN survival was assessed by fluorogold retrograde axonal tracing in major pelvic ganglia (MPG). Unmyelinated axons in the CNs were quantitated by electron microscopy.

MAIN OUTCOME MEASURES

Erectile function recovery, CN survival, and unmyelinated CN axon preservation in response to GGF2 treatment following BCNI.

RESULTS

Erectile function was decreased (P < 0.05) after BCNI, and it was improved (P < 0.05) by all doses of GGF2. The number of fluorogold-labeled cells in the MPG was reduced (P < 0.05) by BCNI and was increased (P < 0.05) by GGF2 (0.5 and 5 mg/kg). The percentage of denervated Schwann cells in the BCNI group was higher (P < 0.05) than that in the sham-treated group and was decreased (P < 0.05) in the GGF2-treated (5 mg/kg) BCNI group. In the BCNI + GGF2 (5 mg/kg) group, the unmyelinated fiber histogram demonstrated a rightward shift, indicating an increased number of unmyelinated axons per Schwann cell compared with the BCNI group.

CONCLUSIONS

GGF2 promotes erectile function recovery following CN injury in conjunction with preserving unmyelinated CN fibers. Our findings suggest the clinical opportunity to develop GGF2 as a neuroprotective therapy for radical prostatectomy.

Neuregulin 1 affects leptin levels, food intake and weight gain in normal-weight, but not obese, db/db mice

AIM

Studies in vitro have highlighted the potential involvement of neuregulin 1 (NRG1) in the regulation of energy metabolism. This effect has also been suggested in vivo, as intracerebroventricular injection of NRG1 reduces food intakes and weight gain in rodents. Thus, it was hypothesised that NRG1 might affect serum leptin levels in mice.

METHODS

Weight, food intakes, energy expenditure, spontaneous physical activity and serum leptin levels were evaluated in normal-weight C57BL/6JRJ mice following intraperitoneal administration of NRG1 (50 μg/kg, three times/week) or saline for 8 weeks. Based on the results of this first experiment, leptin-resistant obese db/db mice were then given NRG1 for 8 weeks.

RESULTS

Leptin serum concentrations were six times higher in C57BL/6JRJ mice treated with NRG1 than in the animals given saline. NRG1 treatment also reduced weight gain by 10% and food intakes by 15% compared with saline treatment, while energy expenditure remained unchanged. In db/db mice, serum leptin concentrations, weight gain, food intakes, energy expenditure and spontaneous physical activity were not altered by NRG1 treatment.

CONCLUSION

The decrease in food intakes and weight gain associated with NRG1 treatment in C57BL/6JRJ mice may be partly explained by increased leptin levels, whereas db/db mice were not affected by the treatment, suggesting resistance to NRG1 in this pathological state.

Neurohypophyseal Neuregulin 1 Is Derived from the Hypothalamus as a Potential Prolactin Modulator

Although neuregulin 1 (Nrg1) has been identified in the rat hypothalamus, the localisation of Nrg1 in the hypothalamus-hypophyseal structure and its functions remain unclear and require further elucidation. In this study, we identified the existence of Nrg1β types I-III in the rat hypothalamus. We demonstrated that Nrg1 was partially localised in somatostatin-positive cells in the periventricular nucleus. It was also co-localised with arginine vasopressin in the supraoptic nucleus, median eminence and pituitary stalk. Nrg1 was also extensively distributed in the posterior pituitary (PP), including the projected neuronal fibres that surround the vascular structure and Herring bodies. Western blotting confirmed that these signals were primarily produced by soluble Nrg1 derived from a 45-kDa Nrg1 precursor mainly identified in the hypothalamus. Similar to Nrg1α, Nrg1β increased the prolactin (PRL) expression in rat pituitary RC-4B/C cells, which can be inhibited by an Akt inhibitor. In addition, Nrg1β had no apparent effect on growth hormone expression at the mRNA or protein levels. Collectively, we conclude that hypothalamic Nrg1 may be transported to the PP as the β form. We further hypothesise that Nrg1β may function via the regulation of PRL expression through a paracrine mechanism.

Homeostasis in C. elegans sleep is characterized by two behaviorally and genetically distinct mechanisms

Biological homeostasis invokes modulatory responses aimed at stabilizing internal conditions. Using tunable photo- and mechano-stimulation, we identified two distinct categories of homeostatic responses during the sleep-like state of Caenorhabditis elegans (lethargus). In the presence of weak or no stimuli, extended motion caused a subsequent extension of quiescence. The neuropeptide Y receptor homolog, NPR-1, and an inhibitory neuropeptide known to activate it, FLP-18, were required for this process. In the presence of strong stimuli, the correlations between motion and quiescence were disrupted for several minutes but homeostasis manifested as an overall elevation of the time spent in quiescence. This response to strong stimuli required the function of the DAF-16/FOXO transcription factor in neurons, but not that of NPR-1. Conversely, response to weak stimuli did not require the function of DAF-16/FOXO. These findings suggest that routine homeostatic stabilization of sleep may be distinct from homeostatic compensation following a strong disturbance.

DOI:http://dx.doi.org/10.7554/eLife.04380.001

The regenerative properties of sleep are required by all animals, with even the simplest animal, the nematode Caenorhabditis elegans, displaying a sleep-like state called lethargus. During development, nematodes must pass through four larval stages en route to adulthood, and the end of each stage is preceded by a period of lethargus lasting 2 to 3 hr.

Human sleep is divided into distinct stages that recur in a prescribed order throughout the night. Nematodes, on the other hand, simply experience alternating periods of activity and stillness as they sleep. Nevertheless, in both species, any disruptions to sleep automatically lead to adjustments of the rest of the sleep cycle to compensate for the disturbance and to ensure that the organism gets an adequate amount of sleep overall.

To date, it has been assumed that a single mechanism is responsible for adjusting the sleep cycle after any disturbance, regardless of its severity. However, Nagy, Tramm, Sanders et al. now show that this is not the case in C. elegans. Sleeping nematodes that were lightly disturbed by exposing them to light or to vibrations—causing them to briefly increase their activity levels—compensated for the disturbance by lengthening their next inactive period. By contrast, worms that were vigorously agitated by stronger vibrations showed a different response: the alternating pattern of stillness and activity was disrupted for several minutes, followed by an overall increase in the length of time spent in the stillness phase.

Experiments using genetically modified worms revealed that these two responses involve distinct molecular pathways. A signaling molecule called neuropeptide Y affects the response to minor sleep disruptions, whereas a transcription factor called DAF-16/FOXO is involved in the corresponding role after major disruptions. Given that neuropeptide Y has already been implicated in sleep regulation in humans and flies, it is not implausible that similar mechanisms may occur in response to disturbances of our own sleep.

DOI:http://dx.doi.org/10.7554/eLife.04380.002

Cellular stress induces a protective sleep-like state in C. elegans

Sleep is recognized to be ancient in origin, with vertebrates and invertebrates experiencing behaviorally quiescent states that are regulated by conserved genetic mechanisms. Despite its conservation throughout phylogeny, the function of sleep remains debated. Hypotheses for the purpose of sleep include nervous-system-specific functions such as modulation of synaptic strength and clearance of metabolites from the brain, as well as more generalized cellular functions such as energy conservation and macromolecule biosynthesis. These models are supported by the identification of synaptic and metabolic processes that are perturbed during prolonged wakefulness. It remains to be seen whether perturbations of cellular homeostasis in turn drive sleep. Here we show that under conditions of cellular stress, including noxious heat, cold, hypertonicity, and tissue damage, the nematode Caenorhabditis elegans engages a behavioral quiescence program. The stress-induced quiescent state displays properties of sleep and is dependent on the ALA neuron, which mediates the conserved soporific effect of epidermal growth factor (EGF) ligand overexpression. We characterize heat-induced quiescence in detail and show that it is indeed dependent on components of EGF signaling, providing physiological relevance to the behavioral effects of EGF family ligands. We find that after noxious heat exposure, quiescence-defective animals show elevated expression of cellular stress reporter genes and are impaired for survival, demonstrating the benefit of stress-induced behavioral quiescence. These data provide evidence that cellular stress can induce a protective sleep-like state in C. elegans and suggest that a deeply conserved function of sleep is to mitigate disruptions of cellular homeostasis.

ErbB1-4-dependent EGF/neuregulin signals and their cross talk in the central nervous system: pathological implications in schizophrenia and Parkinson's disease

Ligands for ErbB1-4 receptor tyrosine kinases, such as epidermal growth factor (EGF) and neuregulins, regulate brain development and function. Thus, abnormalities in their signaling are implicated in the etiology or pathology of schizophrenia and Parkinson's disease. Among the ErbB receptors, ErbB1, and ErbB4 are expressed in dopamine and GABA neurons, while ErbB1, 2, and/or 3 are mainly present in oligodendrocytes, astrocytes, and their precursors. Thus, deficits in ErbB signaling might contribute to the neurological and psychiatric diseases stemming from these cell types. By incorporating the latest cancer molecular biology as well as our recent progress, we discuss signal cross talk between the ErbB1-4 subunits and their neurobiological functions in each cell type. The potential contribution of virus-derived cytokines (virokines) that mimic EGF and neuregulin-1 in brain diseases are also discussed.

Depression, survival, and epidermal growth factor receptor genotypes in patients with metastatic non-small cell lung cancer

OBJECTIVE

Although depression appears to be associated with worse survival from cancer, the underlying mechanisms of this association are unknown. Tumor epidermal growth factor receptor (EGFR) genotype is a known predictor of survival in metastatic non-small cell lung cancer (NSCLC) and appears to be associated with depression. We hypothesized that tumor EGFR genotype may account for a relationship between depression and survival in this population. We investigated this possible relationship in a cohort of patients with metastatic NSCLC, in which we had previously demonstrated an association between depression and worse survival.

METHOD

A cohort of 151 patients with newly diagnosed metastatic NSCLC were enrolled and followed in a randomized controlled trial of early palliative care. At enrollment, 150 had depression assessed with the Patient Health Questionnaire-9 (PHQ-9), and categorical scoring for major depressive syndrome (MDS) was used for analyses. Patients with tumor tissue available underwent EGFR genotyping. Associations with survival were tested using Cox proportional hazards models, adjusting for potential confounders.

RESULTS

Twenty-one patients (14.0%) met criteria for MDS. Forty-four patients (29.3%) had EGFR genotyping, and 17 (38.6%) of these harbored EGFR mutations. Patients with EGFR mutations had significantly lower PHQ-9 scores (p = 0.03), and none met criteria for depression. EGFR mutations were significantly associated with superior survival (p = 0.02). When both depression and EGFR genotype were simultaneously entered into the model, only EGFR mutations remained significantly associated with survival (p = 0.02), and the effect of depression was attenuated.

SIGNIFICANCE OF RESULTS

Depression is associated with worse survival in metastatic NSCLC, and this relationship may be at least partially explained by tumor EGFR genotype. Further study into whether depression could be associated with specific biologic properties of cancer that vary by genotype is warranted.

Prevalence, putative mechanisms, and current management of sleep problems during chemotherapy for cancer

Sleep problems are highly prevalent in cancer patients undergoing chemotherapy. This article reviews existing evidence on etiology, associated symptoms, and management of sleep problems associated with chemotherapy treatment during cancer. It also discusses limitations and methodological issues of current research. The existing literature suggests that subjectively and objectively measured sleep problems are the highest during the chemotherapy phase of cancer treatments. A possibly involved mechanism reviewed here includes the rise in the circulating proinflammatory cytokines and the associated disruption in circadian rhythm in the development and maintenance of sleep dysregulation in cancer patients during chemotherapy. Various approaches to the management of sleep problems during chemotherapy are discussed with behavioral intervention showing promise. Exercise, including yoga, also appear to be effective and safe at least for subclinical levels of sleep problems in cancer patients. Numerous challenges are associated with conducting research on sleep in cancer patients during chemotherapy treatments and they are discussed in this review. Dedicated intervention trials, methodologically sound and sufficiently powered, are needed to test current and novel treatments of sleep problems in cancer patients receiving chemotherapy. Optimal management of sleep problems in patients with cancer receiving treatment may improve not only the well-being of patients, but also their prognosis given the emerging experimental and clinical evidence suggesting that sleep disruption might adversely impact treatment and recovery from cancer.

Evaluating the links between schizophrenia and sleep and circadian rhythm disruption

Sleep and circadian rhythm disruption (SCRD) and schizophrenia are often co-morbid. Here, we propose that the co-morbidity of these disorders stems from the involvement of common brain mechanisms. We summarise recent clinical evidence that supports this hypothesis, including the observation that the treatment of SCRD leads to improvements in both the sleep quality and psychiatric symptoms of schizophrenia patients. Moreover, many SCRD-associated pathologies, such as impaired cognitive performance, are routinely observed in schizophrenia. We suggest that these associations can be explored at a mechanistic level by using animal models. Specifically, we predict that SCRD should be observed in schizophrenia-relevant mouse models. There is a rapidly accumulating body of evidence which supports this prediction, as summarised in this review. In light of these emerging data, we highlight other models which warrant investigation, and address the potential challenges associated with modelling schizophrenia and SCRD in rodents. Our view is that an understanding of the mechanistic overlap between SCRD and schizophrenia will ultimately lead to novel treatment approaches, which will not only ameliorate SCRD in schizophrenia patients, but also will improve their broader health problems and overall quality of life.

Neurobiological studies of fatigue

Fatigue is a symptom associated with many disorders, is especially common in women and in older adults, and can have a huge negative influence on quality of life. Although most past research on fatigue uses human subjects instead of animal models, the use of appropriate animal models has recently begun to advance our understanding of the neurobiology of fatigue. In this review, results from animal models using immunological, developmental, or physical approaches to study fatigue are described and compared. Common across these animal models is that fatigue arises when a stimulus induces activation of microglia and/or increased cytokines and chemokines in the brain. Neurobiological studies implicate structures in the ascending arousal system, sleep executive control areas, and areas important in reward. In addition, the suprachiasmatic nucleus clearly plays an important role in homeostatic regulation of the neural network mediating fatigue. This nucleus responds to cytokines, shows decreased amplitude firing rate output in models of fatigue, and responds to exercise, one of our few treatments for fatigue. This is a young field but very important as the symptom of fatigue is common across many disorders and we do not have effective treatments.

Central role of the EGF receptor in neurometabolic aging

A strong connection between neuronal and metabolic health has been revealed in recent years. It appears that both normal and pathophysiological aging, as well as neurodegenerative disorders, are all profoundly influenced by this "neurometabolic" interface, that is, communication between the brain and metabolic organs. An important aspect of this "neurometabolic" axis that needs to be investigated involves an elucidation of molecular factors that knit these two functional signaling domains, neuronal and metabolic, together. This paper attempts to identify and discuss a potential keystone signaling factor in this "neurometabolic" axis, that is, the epidermal growth factor receptor (EGFR). The EGFR has been previously demonstrated to act as a signaling nexus for many ligand signaling modalities and cellular stressors, for example, radiation and oxidative radicals, linked to aging and degeneration. The EGFR is expressed in a wide variety of cells/tissues that pertain to the coordinated regulation of neurometabolic activity. EGFR signaling has been highlighted directly or indirectly in a spectrum of neurometabolic conditions, for example, metabolic syndrome, diabetes, Alzheimer's disease, cancer, and cardiorespiratory function. Understanding the positioning of the EGFR within the neurometabolic domain will enhance our appreciation of the ability of this receptor system to underpin highly complex physiological paradigms such as aging and neurodegeneration.

Cetuximab and cancers of the head and neck: tapping the circadian rhythm

Proteins in tissue obtained from human skin and oral mucosa have shown a significant circadian rhythm, with the peak expression of p27 at 6:00 AM (early G1-phase marker), p53 at 10:50 AM (late G1-phase marker) and cyclin-E at 2:50 PM (S-phase marker). Patients irradiated in late afternoon/evening have shown a higher grade of mucositis and dermatitis. Studies evaluating the effect of EGFR blockade on cell cycle progression in several human cell types, including A431 squamous epithelial carcinoma cells, suggest that cetuximab leads to cell cycle arrest in G1 phase. On concurrent administration with radiation, mucositis and dermatitis are its main side-effects. So we can hypothesize that cetuximab administration after 11:00 AM would decrease these toxicities. In addition, its administration prior to late afternoon/evening (3:00 PM) can further reduce the radiation associated mucositis and dermatitis due to the occurrence of S-phase during this time and thus increase the therapeutic benefit.

ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system

Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders.

Cetuximab and circadian chronomodulated chemotherapy as salvage treatment for metastatic colorectal cancer (mCRC): safety, efficacy and improved secondary surgical resectability

BACKGROUND

Circadian rhythm disruption was linked to high serum levels of Transforming Growth Factor Receptor α, an Epidermal Growth Factor Receptor (EGFR) ligand and poor survival in patients with metastatic colorectal cancer (mCRC). We hypothesized that EGFR blockade with cetuximab would enhance the activity of chronotherapy as a result of improved circadian coordination.

METHODS

All the patients with mCRC referred to our unit for progression on prior chemotherapy over a 30-month-period received weekly cetuximab and fortnightly chronotherapy.

RESULTS

Fifty-six patients were treated with a median of six courses of fluoropyrimidine-based chemotherapy and irinotecan (61%), oxaliplatin (25%) or both (14%) after a median of three prior regimens. We found no EFGR amplification by FISH in the tumor of 27 consecutive patients. Acneiform rash and diarrhea were the most common toxicities. Objective response rate was 32.1% and positively correlated with rash grade (p = 0.025). None of the responders had K-Ras mutation in their tumor. Median progression-free and overall survival were 4.6 and 13.7 months, respectively. Complete macroscopic resections of metastases in liver, lung or other abdominopelvic sites were performed following tumor downstaging by the treatment regimen in 11 patients (21%), 8 of whom being alive at 3 years. These figures are twice as high as those reported for first-line combination of cetuximab with conventional chemotherapy or for third line chronotherapy.

CONCLUSIONS

The addition of cetuximab to chronotherapy allowed safe and effective therapeutic control of metastases, including their complete resection, despite previous failure of several treatment regimens.

Circadian Disruption, Fatigue, and Anorexia Clustering in Advanced Cancer Patients: Implications for Innovative Therapeutic Approaches

A disruption of the circadian timing system, as identified by monitoring of marker biorhythms, is common in cancer patients. The recording of the rest—activity rhythm with a wrist actigraph has been commonly used. This noninvasive monitoring allows a robust estimation of circadian disruption. The authors have previously found that altered patterns of circadian rest—activity rhythms are significantly and independently associated with the severity of fatigue and anorexia in patients with metastatic colorectal cancer. Elevated proinflammatory cytokines could partly account for this circadian disruption and its associated constitutional symptoms. Here, the authors present and discuss the data supporting the hypothesis that circadian disruption is often associated with fatigue and anorexia, which in turn further alter and dampen circadian synchronization, thus, creating a vicious cycle. This body of evidence paves the path for innovative therapeutic approaches targeting the circadian timing system in an effort to diminish constitutional symptoms induced by cancer and some anticancer treatments.

The genetic and molecular regulation of sleep: from fruit flies to humans

It has been known for a long time that genetic factors affect sleep quantity and quality. Genetic screens have identified several mutations that affect sleep across species, pointing to an evolutionary conserved regulation of sleep. Moreover, it has also been recognized that sleep affects gene expression. These findings have given valuable insights into the molecular underpinnings of sleep regulation and function that might lead the way to more efficient treatments for sleep disorders.

Behavioral effects of systemic transforming growth factor-alpha in Syrian hamsters

The growth factor, transforming growth factor-alpha (TGF-alpha) is strongly expressed in the hypothalamic circadian pacemaker, the suprachiasmatic nucleus (SCN). TGF-alpha is one of several SCN peptides recently suggested to function as a circadian output signal for the regulation of locomotor activity rhythms in nocturnal rodents. When infused in the brain, TGF-alpha suppresses activity. TGF-alpha suppresses other behaviors as well including feeding, resulting in weight loss. Elevated TGF-alpha is correlated with some cancers, and it is possible the TGF-alpha and its receptor, the epidermal growth factor receptor (EGFR), mediate fatigue and weight loss associated with cancer. If true for cancers outside of the brain, then systemic TGF-alpha should also affect behavior. We tested this hypothesis in hamsters with intraperitoneal injections or week-long subcutaneous infusions of TGF-alpha. Both treatments suppressed activity and infusions caused reduced food consumption and weight loss. To identify areas of the brain that might mediate these effects of systemic TGF-alpha, we used immunohistochemistry to localize cells with an activated MAP kinase signaling pathway (phosphorylated ERK1). Cells were activated in two hypothalamic areas, the paraventricular nucleus and a narrow region surrounding the third ventricle. These sites could not only be targets of TGF-alpha produced in the SCN but could also mediate effects of elevated TGF-alpha from tumors both within and outside the central nervous system.

Remodeling the clock: coactivators and signal transduction in the circadian clockworks

Most organisms on earth such as cyanobacteria, fungi, plants, insects, animals, and humans synchronize their physiological and behavioral activities with the environmental cycles of day and night. Significant progress has been made in unraveling the genetic components that constitute a molecular circadian clock, which facilitates the temporal control of physiology and behavior. Clock genes assemble interlocked transcriptional/translational feedback loops that underlie the circadian oscillations. Recent investigations revealed that posttranslational regulation of clock proteins is crucial for functioning of the molecular oscillator and for precise temporal control of circadian transcription. This review provides an overview of the homologous clockworks in Drosophila and mammals, with a special focus on recent insights in the posttranslational regulation of clock proteins as well as the role of coactivators, repressors, and signal transduction for circadian controlled genome-wide transcription. The emerging mechanisms of clock gene regulation provide an understanding of the temporal control of transcription in general and the circadian orchestration of physiology and behavior in particular.

Deficiency of TNFalpha converting enzyme (TACE/ADAM17) causes a lean, hypermetabolic phenotype in mice

Energy homeostasis involves central nervous system integration of afferent inputs that coordinately regulate food intake and energy expenditure. Here, we report that adult homozygous TNFalpha converting enzyme (TACE)-deficient mice exhibit one of the most dramatic examples of hypermetabolism yet reported in a rodent system. Because this effect is not matched by increased food intake, mice lacking TACE exhibit a lean phenotype. In the hypothalamus of these mice, neurons in the arcuate nucleus exhibit intact responses to reduced fat mass and low circulating leptin levels, suggesting that defects in other components of the energy homeostasis system explain the phenotype of Tace(DeltaZn/DeltaZn) mice. Elevated levels of uncoupling protein-1 in brown adipose tissue from Tace(DeltaZn/DeltaZn) mice when compared with weight-matched controls suggest that deficient TACE activity is linked to increased sympathetic outflow. These findings collectively identify a novel and potentially important role for TACE in energy homeostasis.

Sleep: dozy worms and sleepy flies

Recent work on quiescent states in Caenorhabditis elegans suggests that worms exhibit behaviours reminiscent of satiety and sleep in mammals. At a molecular level, signalling through the EGF receptor and protein kinase G promotes quiescent states in both worms and flies, suggesting conserved mechanisms for sleep-like behaviours.

Cancer symptom complexes related to alterations in molecular circadian axis signaling

One of the most common symptoms in cancer patients is fatigue that is often associated with appetite loss and sleep disruption. Quality of life indices and objective measures of these symptoms are now possible and continue to improve our understanding of how these symptoms are caused. Disruption of 24 hour rest/activity patterns measured by actigraphy is one example where there is overlap of the objective measurement of symptoms and the circadian axis. This paper reviews new data relevant to understanding mechanisms involving inhibition of the circadian system and the production of symptom complexes in cancer patients through hypothalamic signaling by tumor produced members of the epidermal growth factor receptor.

Epidermal growth factor signaling induces behavioral quiescence in Caenorhabditis elegans

The epidermal growth factor receptor (EGFR)/ErbB receptor tyrosine kinases regulate several aspects of development, including the development of the mammalian nervous system. ErbB signaling also has physiological effects on neuronal function, with influences on synaptic plasticity and daily cycles of activity. However, little is known about the effectors of EGFR activation in neurons. Here we show that EGF signaling has a nondevelopmental effect on behavior in Caenorhabditis elegans. Ectopic expression of the EGF-like ligand LIN-3 at any stage induces a reversible cessation of feeding and locomotion. These effects are mediated by neuronal EGFR (also called LET-23) and phospholipase C-gamma (PLC-gamma), diacylglycerol-binding proteins, and regulators of synaptic vesicle release. Activation of EGFR within a single neuron, ALA, is sufficient to induce a quiescent state. This pathway modulates the cessation of pharyngeal pumping and locomotion that normally occurs during the lethargus period that precedes larval molting. Our results reveal an evolutionarily conserved role for EGF signaling in the regulation of behavioral quiescence.

Hepatic mitochondrial function and brain tumours

PURPOSE OF REVIEW

Therapeutic advances remain modest for patients with malignant brain tumours, due in part to inadequate ability of in-vitro models to mimic the consequences of tumour progression in vivo, which include profound immunosuppression, cytokine dysregulation and microvascular proliferation. This review summarizes recent findings on the wasting consequences of glioma growth, including changes in hepatic metabolism caused by the tumour.

RECENT FINDINGS

Release of proinflammatory cytokines by gliomas leads to anorexia, a sensation of tiredness and fatigue associated with sleep deprivation. The cachexia and associated decrease in relative liver mass that are observed in rats with the most aggressive gliomas may be accounted for by increased activity of the Cori cycle, with the intermediary metabolism of the glioma-influenced liver being directed toward energy utilization rather than energy storage. In these conditions, liver mitochondria exhibit abnormal biogenesis, together with modifications to water dynamics and ion content.

SUMMARY

Improved patient care will result from better understanding of the interactions between brain tumour cells and the immune system, and use of nutritional metabolic therapy to protect tumour-influenced hepatocytes and their mitochondria may improve outcomes.

Heterozygous neuregulin 1 mice are more sensitive to the behavioural effects of Delta9-tetrahydrocannabinol

RATIONALE

Cannabis use may precipitate schizophrenia especially if the individual has a genetic vulnerability to this mental disorder. Human and animal research indicates that neuregulin 1 (Nrg1) is a susceptibility gene for schizophrenia.

OBJECTIVES

The aim of this study was to investigate whether dysfunction in the Nrg1 gene modulates the behavioural effects of Delta(9)-tetrahydrocannabinol (THC), the major psychotropic component of cannabis.

MATERIALS AND METHODS

Heterozygous Nrg1 transmembrane-domain knockout mice (Nrg1 HET) were treated with acute THC (0, 5 or 10 mg/kg i.p.) 30 min before being tested using open field (OF), hole board (HB), light-dark (LD), elevated plus maze (EPM), social interaction (SI) and prepulse inhibition (PPI) tests.

RESULTS

Nrg1 HET mice showed differences in baseline behaviour with regard to locomotor activity, exploration and anxiety. More importantly, they were more sensitive to the locomotor suppressant actions of THC compared to wild type-like (WT) mice. In addition, Nrg1 HET mice expressed a greater THC-induced enhancement in % PPI than WT mice. The effects of THC on anxiety-related behaviour were task-dependent, with Nrg1 HET mice being more susceptible than WT mice to the anxiogenic effects of THC in LD, but not in the EPM, SI and OF tests.

CONCLUSIONS

Nrg1 HET mice were more sensitive to the acute effects of THC in an array of different behaviours including those that model symptoms of schizophrenia. It appears that variation in the schizophrenia-related neuregulin 1 gene alters the sensitivity to the behavioural effects of cannabinoids.

Expression of Tgfα in the suprachiasmatic nuclei of nocturnal and diurnal rodents

Transforming growth factor alpha (TGFalpha) in the suprachiasmatic nuclei (SCN) has been proposed as an inhibitory signal involved in the control of daily locomotor activity. This assumption is based mainly on studies performed in nocturnal hamsters. To test whether the transcriptional regulation of Tgfalpha can be correlated with the timing of overt activity in other species, we compared Tgfalpha expression in the SCN of nocturnal Swiss mice and of diurnal Arvicanthis housed under a light/dark cycle (LD) or transferred to constant darkness (DD). In agreement with data on hamsters, Tgfalpha mRNA levels in the mouse SCN showed peak and trough levels around (subjective) dawn and dusk, respectively, roughly corresponding to the period of rest and activity in this species. In contrast, in Arvicanthis housed in DD, the circadian rhythm of SCN Tgfalpha was similar to that of the mice in spite of opposite phasing of locomotor activity. Furthermore, in Arvicanthis exposed to LD, Tgfalpha mRNA levels were constitutively high throughout the day. A tonic role of light in the regulation of Tgfalpha in Arvicanthis was confirmed by an increased expression of Tgfalpha in response to a 6-h exposure to light during daytime in animals otherwise kept in DD. In conclusion, this study shows that, contrary to what is observed in mice, Tgfalpha mRNA levels in the SCN of Arvicanthis do not match timing of locomotor activity and are modulated by light.

Wildtype epidermal growth factor receptor (Egfr) is not required for daily locomotor or masking behavior in mice

Background

Recent studies have implicated the epidermal growth factor receptor (EGFR) within the subparaventricular zone as being a major mediator of locomotor and masking behaviors in mice. The results were based on small cohorts of mice homozygous for the hypomorphic Egfr^wa2 allele on a mixed, genetically uncontrolled background, and on intraventricular infusion of exogenous EGFR ligands. Subsequenlty, a larger study using the same genetically mixed background failed to replicate the original findings. Since both previous approaches were susceptible to experimental artifacts related to an uncontrolled genetic background, we analyzed the locomotor behaviors in Egfr^wa2 mutant mice on genetically defined, congenic backgrounds.

Methods

Mice carrying the Egfr^wa2 hypomorphic allele were bred to congenicity by backcrossing greater than ten generations onto C57BL/6J and 129S1/SvImJ genetic backgrounds. Homozygous Egfr^wa2 mutant and wildtype littermates were evaluated for defects in locomotor and masking behaviors.

Results

Mice homozygous for Egfr^wa2 showed normal daily locomotor activity and masking indistinguishable from wildtype littermates at two light intensities (200–300 lux and 400–500 lux).

Conclusion

Our results demonstrate that reduced EGFR activity alone is insufficient to perturb locomotor and masking behaviors in mice. Our results also suggest that other uncontrolled genetic or environmental parameters confounded previous experiments linking EGFR activity to daily locomotor activity and provide a cautionary tale for genetically uncontrolled studies.

Systems analysis of circadian time-dependent neuronal epidermal growth factor receptor signaling

BACKGROUND

Identifying the gene regulatory networks governing physiological signal integration remains an important challenge in circadian biology. Epidermal growth factor receptor (EGFR) has been implicated in circadian function and is expressed in the suprachiasmatic nuclei (SCN), the core circadian pacemaker. The transcription networks downstream of EGFR in the SCN are unknown but, by analogy to other SCN inputs, we expect the response to EGFR activation to depend on circadian timing.

RESULTS

We have undertaken a systems-level analysis of EGFR circadian time-dependent signaling in the SCN. We collected gene-expression profiles to study how the SCN response to EGFR activation depends on circadian timing. Mixed-model analysis of variance (ANOVA) was employed to identify genes with circadian time-dependent EGFR regulation. The expression data were integrated with transcription-factor binding predictions through gene group enrichment analyses to generate robust hypotheses about transcription-factors responsible for the circadian phase-dependent EGFR responses.

CONCLUSION

The analysis results suggest that the transcriptional response to EGFR signaling in the SCN may be partly mediated by established transcription-factors regulated via EGFR transcription-factors (AP1, Ets1, C/EBP), transcription-factors involved in circadian clock entrainment (CREB), and by core clock transcription-factors (Ror alpha). Quantitative real-time PCR measurements of several transcription-factor expression levels support a model in which circadian time-dependent EGFR responses are partly achieved by circadian regulation of upstream signaling components. Our study suggests an important role for EGFR signaling in SCN function and provides an example for gaining physiological insights through systems-level analysis.

Recent progress in animal modeling of immune inflammatory processes in schizophrenia: implication of specific cytokines

Epidemiologic studies demonstrate significant environmental impact of maternal viral infection and obstetric complications on the risk of schizophrenia and indicate their detrimental influences on brain development in this disorder. Based on these findings, animal models for schizophrenia have been established using double stranded RNA, bacterial lipopolysaccharides, hippocampal lesion, or prenatal/perinatal ischemia. Key molecules regulating such immune/inflammatory reactions are cytokines, which are also involved in brain development, regulating dopaminergic and GABAergic differentiation, and synaptic maturation. Specific members of the cytokine family, such as interleukin-1, epidermal growth factor, and neuregulin-1, are induced after infection and brain injury; therefore, certain cytokines are postulated to have a central role in the neurodevelopmental defects of schizophrenia. Recently, to test this hypothesis, a variety of cytokines were administered to rodent pups. Cytokines administered in the periphery penetrated the immature blood-brain barrier and perturbed phenotypic neural development. Among the many cytokines examined, epidermal growth factor (or potentially other ErbB1 ligands) and interleukin-1 specifically induced the most severe and persistent behavioral and cognitive abnormalities, most of which were ameliorated by antipsychotics. These animal experiments illustrate that, during early development, these cytokine activities in the periphery perturbs normal brain development and impairs later psychobehavioral and/or cognitive traits. The neurodevelopmental and behavioral consequences of prenatal/perinatal cytokine activity are compared with those of other schizophrenia models and cytokine interactions with genes are also discussed in this review.