Resetting the Biological Clock: Mediation of Nocturnal Circadian Shifts by Glutamate and NO

Ding, JM; Chen, D; Weber, E. Todd; Faiman, Lia E.; Rea, Michael A.; Gillette, MU

doi:10.1126/science.7527589

Cited by 529 publications

(477 citation statements)

References 56 publications

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“…Additional known contributors to time-of-day gated signaling cascades were evaluated in the immortalized SCN cells. Bands against neuronal NOS, a mediator of nighttime phase shifts induced by light (31), were evident at 155 kDa in SCN 2.2 extracts, consistent with SCN tissue and previous reports (Fig. 4A) (48).…”

Section: Resultssupporting

confidence: 91%

Immortalized Suprachiasmatic Nucleus Cells Express Components of Multiple Circadian Regulatory Pathways

Hurst

Earnest

Gillette

2002

Biochemical and Biophysical Research Communications

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We undertook an extensive antigenic characterization of the SCN 2.2 cell line in order to further evaluate whether the line expresses components of circadian regulatory pathways common to the hypothalamic suprachiasmatic nucleus (SCN), the central circadian clock in mammals. We found that differentiated SCN 2.2 cultures expressed a broad range of putative clock genes, as well as components of daytime, nighttime, and crepuscular circadian regulatory pathways found within the SCN in vivo. The line also exhibits several antigens that are highly expressed in a circadian pattern and/or differentially localized in the SCN relative to other hypothalamic regions. Expression of a broad complement of circadian regulatory proteins and putative clock genes further support growing evidence in recent reports that the SCN 2.2 cell line is an appropriate model for investigating the regulation of central mammalian pacemaker. © 2002 Elsevier Science (USA) Key Words: period; cryptochrome; casein kinase; PACAP; PKA; PKC; PKG; NOS; I1; VGF.The central biological pacemaker in mammals lies in the hypothalamic suprachiasmatic nucleus (SCN). The SCN drives circadian behavior, expresses rhythmic gene expression and integrates external stimuli in order to synchronize molecular timekeeping mechanisms with changing environmental conditions. Receptivity to phase shifting stimuli is gated by the circadian state of the central pacemaker. This gating behavior is most clearly demonstrated by the sensitivity of the SCN to light during the night phase, but not during the day phase. All photic, social and hormonal influences on the circadian clock are integrated at the cellular level through multiple signaling pathways within the SCN.The complexity of interacting signaling pathways involved in regulation of the SCN has encouraged researchers to seek cell culture systems to complement in vivo analysis of the mammalian circadian clock. Whether a cell line exhibits central or peripheral circadian clock characteristics complicates selection of an appropriate model system. To provide useful applications for central mammalian pacemaker research, cell line models must exhibit persistent self-sustained oscillations in circadian gene products, restore animal circadian rhythms in SCN-lesioned hosts and exhibit time-dependent responses to stimuli through regulatory pathways that characterize SCN function. Rhythmic gene expression has been demonstrated in NIH/ 3T3 fibroblasts, Rat-1 fibroblasts and spontaneously immortalized embryonic mouse fibroblasts after synchronizing signals (1-5). However, there is no published evidence that these lines express spontaneous, self-sustained rhythms or rescue rhythms in SCNlesioned animals (5, 6). In contrast, another cell line derived from fetal rat SCN, the SCN 2.2 cell line, exhibits endogenous spontaneous circadian rhythmicity in vitro (5, 7). We have focused on the SCN 2.2 line to further assess its usefulness as a model system for studying the mammalian central circadian pacemaker.The SCN 2.2 cell line is a pluripoten...

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Section: Resultssupporting

confidence: 91%

Immortalized Suprachiasmatic Nucleus Cells Express Components of Multiple Circadian Regulatory Pathways

Hurst

Earnest

Gillette

2002

Biochemical and Biophysical Research Communications

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“…[20][21][22][23] Alterations in sGC expression and function in the brain in cirrhotic patients, therefore, could relate to the neuropsychiatric symptoms such as sleep disturbances and memory …”

Section: Discussionmentioning

confidence: 99%

Region selective alterations of soluble guanylate cyclase content and modulation in brain of cirrhotic patients

et al. 2002

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Modulation of soluble guanylate cyclase (sGC) by nitric oxide (NO) is altered in brain from experimental animals with hyperammonemia with or without liver failure. The aim of this work was to assess the content and modulation of sGC in brain in chronic liver failure in humans. Expression of the ␣-1, ␣-2, and ␤-1 subunits of sGC was measured by immunoblotting in autopsied frontal cortex and cerebellum from cirrhotic patients and controls. The contents of ␣-1 and ␣-2 subunits of guanylate cyclase was increased both in cortex and cerebellum, whereas the ␤-1 subunit was not affected. Addition of the NO-generating agent S-nitroso-N-acetyl-penicillamine (SNAP) to homogenates of frontal cortex from controls increased the activity of sGC 87-fold, whereas, in homogenates from cirrhotic patients, the increase was significantly higher (183-fold). In contrast, in cerebellum, activation of guanylate cyclase by NO was significantly lower in patients (156-fold) than in controls (248-fold). A similar regional difference was found in rats with portacaval anastomosis. In conclusion, these findings show that the NO-guanylate cyclase signal transduction pathway is strongly altered in brain in patients with chronic liver failure and that the effects are different in different brain areas. Given that activation of sGC by NO in brain is involved in the modulation of important cerebral processes such as intercellular communication, learning and memory, and the sleep-wake cycle, these changes could be implicated in the pathogenesis of hepatic encephalopathy in these patients. (HEPATOLOGY 2002;36:1155-1162 T he pathophysiologic mechanisms responsible for hepatic encephalopathy (HE) in chronic liver failure are incompletely understood. However, disruption of neurotransmitter systems has increasingly been implicated. In particular, selective alterations of glutamatergic and monoaminergic receptor sites have been reported in both experimental animal models of HE 1,2 and the brains of human cirrhotic patients. 3,4 Many of these receptors are functionally coupled to the nitric oxide (NO) cyclic guanosine monophosphate (cGMP) signal transduction pathway, which serves to amplify the postsynaptic response to receptor activation.Previous studies provide evidence for a role for this signal transduction pathway in the mediation of important cerebral functions, including regulation of the sleepwake cycle and some components of learning and memory, abnormalities of which form part of the spectrum of neuropsychiatric symptoms, which characterize HE in chronic liver failure. Furthermore, recent studies in experimental chronic liver failure reveal significant alterations in expression of key components of this signal transduction pathway. Such evidence includes increased expression and activities of neuronal nitric oxide synthase (nNOS) 5 and of the ␣ subunit of soluble guanylate cyclase (sGC). 6 The purpose of the present study was, therefore, to evaluate the NO-cGMP signal transduction pathway in relation to human HE. To accomplish this, the content o...

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“…Single-unit spontaneous activity of SCN neurons was recorded, as described previously (38). Activity was measured in 4-min bins.…”

Section: Methodsmentioning

confidence: 99%

Mass spectrometry-based discovery of circadian peptides

Hatcher

Atkins

Annangudi

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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151

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A significant challenge to understanding dynamic and heterogeneous brain systems lies in the chemical complexity of secreted intercellular messengers that change rapidly with space and time. Two solid-phase extraction collection strategies are presented that relate time and location of peptide release with mass spectrometric characterization. Here, complex suites of peptide-based cell-to-cell signaling molecules are characterized from the mammalian suprachiasmatic nucleus (SCN), site of the master circadian clock. Observed SCN releasates are peptide rich and demonstrate the corelease of established circadian neuropeptides and peptides with unknown roles in circadian rhythms. Additionally, the content of SCN releasate is stimulation specific. Stimulation paradigms reported to alter clock timing, including electrical stimulation of the retinohypothalamic tract, produce releasate mass spectra that are notably different from the spectra of compounds secreted endogenously over the course of the 24-h cycle. In addition to established SCN peptides, we report the presence of proSAAS peptides in releasates. One of these peptides, little SAAS, exhibits robust retinohypothalamic tract-stimulated release from the SCN, and exogenous application of little SAAS induces a phase delay consistent with light-mediated cues regulating circadian timing. These mass spectrometry-based analyses provide a new perspective on peptidergic signaling within the SCN and demonstrate that the integration of secreted compounds with information relating time and location of release generates new insights into intercellular signaling in the brain.little SAAS ͉ neuropeptides ͉ solid-phase extraction ͉ peptidomics ͉ suprachiasmatic nucleus A fundamental component of cell-to-cell signaling in the brain is the release of endogenously derived neuropeptidebased transmitters and modulators within dynamic neural networks. Neuropeptides include a broad set of structurally diverse molecules that are physiologically active at low concentrations and localize across heterogeneous brain regions, particularly throughout neuroendocrine systems. These properties contribute marked chemical complexity to neurotransmission within heterogeneous and dynamic brain systems. Directly acquiring releasate information about chemical content, release site distribution, and stimulation dependence is a significant challenge to the study of neuronal networks incorporating neuropeptide intercellular signaling.This article describes the use of several unique peptide sampling approaches to characterize chemically complex releasates from the rat suprachiasmatic nucleus (SCN), the site of the master circadian clock (1, 2). The SCN is highly innervated with peptidergic efferents, afferents, and interneurons (3). Moreover, SCN humoral signals are critical elements for the coordination of biological rhythms because SCN transplants can restore aspects of circadian rhythms in SCN-ablated animals (4). In the present work, SCN releasates were collected and concentrated directly from brain sl...

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Resetting the Biological Clock: Mediation of Nocturnal Circadian Shifts by Glutamate and NO

Cited by 529 publications

References 56 publications

Immortalized Suprachiasmatic Nucleus Cells Express Components of Multiple Circadian Regulatory Pathways

Immortalized Suprachiasmatic Nucleus Cells Express Components of Multiple Circadian Regulatory Pathways

Region selective alterations of soluble guanylate cyclase content and modulation in brain of cirrhotic patients

Mass spectrometry-based discovery of circadian peptides

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