Predominant role by CaM kinase in NPY Y(1) receptor signaling: involvement of CREB [corrected]

The Role of Neuropeptide Y in the Nucleus Accumbens

Neuropeptide Y (NPY), an abundant peptide in the central nervous system, is expressed in neurons of various regions throughout the brain. The physiological and behavioral effects of NPY are mainly mediated through Y1, Y2, and Y5 receptor subtypes, which are expressed in regions regulating food intake, fear and anxiety, learning and memory, depression, and posttraumatic stress. In particular, the nucleus accumbens (NAc) has one of the highest NPY concentrations in the brain. In this review, we summarize the role of NPY in the NAc. NPY is expressed principally in medium-sized aspiny neurons, and numerous NPY immunoreactive fibers are observed in the NAc. Alterations in NPY expression under certain conditions through intra-NAc injections of NPY or receptor agonists/antagonists revealed NPY to be involved in the characteristic functions of the NAc, such as alcohol intake and drug addiction. In addition, control of mesolimbic dopaminergic release via NPY receptors may take part in these functions. NPY in the NAc also participates in fat intake and emotional behavior. Accumbal NPY neurons and fibers may exert physiological and pathophysiological actions partly through neuroendocrine mechanisms and the autonomic nervous system.

NPY binds with heme to form a NPY–heme complex: enhancing peroxidase activity in free heme and promoting NPY nitration and inactivation

NPY binding with heme enhances the peroxidase activity of free heme, resulting in the important tyrosine nitration, which will attenuate its bioactivity.

Neuropeptide Y (NPY) and posttraumatic stress disorder (PTSD): A translational update

Posttraumatic stress disorder (PTSD) is a trauma-evoked syndrome, with variable prevalence within the human population due to individual differences in coping and resiliency. In this review, we discuss evidence supporting the relevance of neuropeptide Y (NPY), a stress regulatory transmitter in PTSD. We consolidate findings from preclinical, clinical, and translational studies of NPY that are of relevance to PTSD with an attempt to provide a current update of this area of research. NPY is abundantly expressed in forebrain limbic and brainstem areas that regulate stress and emotional behaviors. Studies in rodents demonstrate a role for NPY in stress responses, anxiety, fear, and autonomic regulation, all relevant to PTSD symptomology. Genetic studies support an association of NPY polymorphisms with stress coping and affect. Importantly, cerebrospinal fluid (CSF) measurements in combat veterans provide direct evidence of NPY association with PTSD diagnosis and symptomology. In addition, NPY involvement in pain, depression, addiction, and metabolism may be relevant to comorbidities associated with PTSD. Collectively, the literature supports the relevance of NPY to PTSD pathophysiology, although knowledge gaps remain. The NPY system is an attractive target in terms of understanding the physiological basis of PTSD as well as treatment of the disorder.

An Indirect Action Contributes to C-Fos Induction in Paraventricular Hypothalamic Nucleus by Neuropeptide Y

Neuropeptide Y (NPY) is a well-established orexigenic peptide and hypothalamic paraventricular nucleus (PVH) is one major brain site that mediates the orexigenic action of NPY. NPY induces abundant expression of C-Fos, an indicator for neuronal activation, in the PVH, which has been used extensively to examine the underlying NPY orexigenic neural pathways. However, PVH C-Fos induction is in discordance with the abundant expression of NPY receptors, a group of inhibitory Gi protein coupled receptors in the PVH, and with the overall role of PVH neurons in feeding inhibition, suggesting a mechanism of indirect action. Here we showed that the ability of NPY on C-Fos induction in the PVH was blunted in conditions of insulin deficiency and fasting, a condition associated with a high level of NPY and a low level of insulin. Moreover, insulin insufficiency blunted C-Fos induction in the PVH by fasting-induced re-feeding, and insulin and NPY induced c-Fos induction in the same group of PVH neurons. Finally, NPY produced normal C-Fos induction in the PVH with disruption of GABA-A receptors. Thus, our results revealed that PVH C-Fos induction by NPY is mediated by an indirect action, which is at least partially mediated by insulin action, but not GABA-A receptors.

Cell-specific expression of calcineurin immunoreactivity within the rat basolateral amygdala complex and colocalization with the neuropeptide Y Y1 receptor

Neuropeptide Y (NPY) produces potent anxiolytic effects via activation of NPY Y1 receptors (Y1r) within the basolateral amygdaloid complex (BLA). The role of NPY in the BLA was recently expanded to include the ability to produce stress resilience and long-lasting reductions in anxiety-like behavior. These persistent behavioral effects are dependent upon activity of the protein phosphatase, calcineurin (CaN), which has long been associated with shaping long-term synaptic signaling. Furthermore, NPY-induced reductions in anxiety-like behavior persist months after intra-BLA delivery, which together indicate a form of neuronal plasticity had likely occurred. To define a site of action for NPY-induced CaN signaling within the BLA, we employed multi-label immunohistochemistry to determine which cell types express CaN and if CaN colocalizes with the Y1r. We have previously reported that both major neuronal cell populations in the BLA, pyramidal projection neurons and GABAergic interneurons, express the Y1r. Therefore, this current study evaluated CaN immunoreactivity in these cell types, along with Y1r immunoreactivity. Antibodies against calcium-calmodulin kinase II (CaMKII) and GABA were used to identify pyramidal neurons and GABAergic interneurons, respectively. A large population of CaN immunoreactive cells displayed Y1r immunoreactivity (90%). Nearly all (98%) pyramidal neurons displayed CaN immunoreactivity, while only a small percentage of interneurons (10%) contained CaN immunoreactivity. Overall, these anatomical findings provide a model whereby NPY could directly regulate CaN activity in the BLA via activation of the Y1r on CaN-expressing, pyramidal neurons. Importantly, they support BLA pyramidal neurons as prime targets for neuronal plasticity associated with the long-term reductions in anxiety-like behavior produced by NPY injections into the BLA.

Dipeptidyl peptidases as survival factors in Ewing sarcoma family of tumors: implications for tumor biology and therapy

Ewing sarcoma family of tumors (ESFT) is a group of aggressive pediatric malignancies driven by the EWS-FLI1 fusion protein, an aberrant transcription factor up-regulating specific target genes, such as neuropeptide Y (NPY) and its Y1 and Y5 receptors (Y5Rs). Previously, we have shown that both exogenous NPY and endogenous NPY stimulate ESFT cell death via its Y1 and Y5Rs. Here, we demonstrate that this effect is prevented by dipeptidyl peptidases (DPPs), which cleave NPY to its shorter form, NPY(3-36), not active at Y1Rs. We have shown that NPY-induced cell death can be abolished by overexpression of DPPs and enhanced by their down-regulation. Both NPY treatment and DPP blockade activated the same cell death pathway mediated by poly(ADP-ribose) polymerase (PARP-1) and apoptosis-inducing factor (AIF). Moreover, the decrease in cell survival induced by DPP inhibition was blocked by Y1 and Y5R antagonists, confirming its dependence on endogenous NPY. Interestingly, similar levels of NPY-driven cell death were achieved by blocking membrane DPPIV and cytosolic DPP8 and DPP9. Thus, this is the first evidence of these intracellular DPPs cleaving releasable peptides, such as NPY, in live cells. In contrast, another membrane DPP, fibroblast activation protein (FAP), did not affect NPY actions. In conclusion, DPPs act as survival factors for ESFT cells and protect them from cell death induced by endogenous NPY. This is the first demonstration that intracellular DPPs are involved in regulation of ESFT growth and may become potential therapeutic targets for these tumors.

Micellar nanomedicine of human neuropeptide Y

Human neuropeptide Y (NPY) is an important biologics that regulates a multitude of physiological functions and could be amenable to therapeutic manipulations in certain disease states. However, rapid (within minutes) enzymatic degradation and inactivation of NPY precludes its development as a drug. Accordingly, we determined whether self-association of NPY with biocompatible and biodegradable sterically stabilized phospholipid micelles (SSM) improves its stability and bioactivity. We found that in saline NPY spontaneously aggregates; however, in the presence of SSM it self-associates with the micelles as monomers. Three NPY molecules self-associate with 1 SSM at saturation. This process stabilizes the peptide in α-helix conformation, abrogates its degradation by dipeptidyl peptidase-4 and potentiates NPY-induced inhibition of cAMP elaboration in SK-N-MC cells. Collectively, these data indicate that self-association of NPY with SSM stabilizes and protects the peptide in active monomeric conformation, thereby amplifying its bioactivity in vitro. We propose further development of NPY in SSM as a novel, long-acting nanomedicine.

FROM THE CLINICAL EDITOR

Human neuropeptide Y (NPY) regulates a multitude of physiological functions and could be amenable to therapeutic manipulations, which is currently limited by its short half life. Self-association of NPY with spherically stabilized micelles (SSM) protects and stabilizes the peptide in active monomeric conformation, thereby amplifying its bioactivity in vitro, enabling future therapeutic considerations.

Neuroscience of alcoholism: molecular and cellular mechanisms

Alcohol use and abuse appear to be related to neuroadaptive changes at functional, neurochemical, and structural levels. Acute and chronic ethanol exposure have been shown to modulate function of the activity-dependent gene transcription factor, cAMP-responsive element binding (CREB) protein in the brain, which may be associated with the development of alcoholism. Study of the downstream effectors of CREB have identified several important CREB-related genes, such as neuropeptide Y, brain-derived neurotrophic factor, activity-regulated cytoskeleton-associated protein, and corticotrophin-releasing factor, that may play a crucial role in the behavioral effects of ethanol and molecular changes in the specific neurocircuitry that underlie both alcohol addiction and a genetic predisposition to alcoholism. Brain chromatin remodeling due to histone covalent modifications may also be involved in mediating the behavioral effects and neuroadaptive changes that occur during ethanol exposure. This review outlines progressive neuroscience research into molecular and epigenetic mechanisms of alcoholism.

Neuropeptide Y signaling in the central nucleus of amygdala regulates alcohol-drinking and anxiety-like behaviors of alcohol-preferring rats

BACKGROUND

The neuropeptide Y (NPY) system of the central nucleus of amygdala (CeA) has been shown to be involved in anxiety and alcoholism. In this study, we investigated the molecular mechanisms by which NPY in the CeA regulates anxiety and alcohol drinking behaviors using alcohol-preferring (P) rats as an animal model.

METHODS

Alcohol-preferring rats were bilaterally cannulated targeting the CeA and infused with artificial cerebrospinal fluid (aCSF) or NPY. Alcohol drinking and anxiety-like behaviors were assessed by the 2-bottle free-choice paradigm and light/dark box (LDB) exploration test, respectively. The levels of NPY and related signaling proteins were determined by the gold immunolabeling procedure. The mRNA levels of NPY were measured by in situ RT-PCR. Double-immunofluorescence labeling was performed to observe the colocalization of NPY and Ca(2+)/calmodulin-dependent protein kinase IV (CaMK IV).

RESULTS

We found that NPY infusion into the CeA produced anxiolytic effects, as measured by the LDB exploration test, and also decreased alcohol intake in P rats. NPY infusion into the CeA significantly increased levels of CaMK IV and phosphorylated cAMP responsive element-binding (pCREB) protein and increased mRNA and protein levels of NPY, but produced no changes in protein levels of CREB or the catalytic alpha-subunit of protein kinase A (PKA-Calpha) in the CeA. We also observed that alcohol intake produced anxiolytic effects in P rats in the LDB test and also increased NPY expression and protein levels of pCREB and PKA-Calpha without modulating protein levels of CREB or CaMK IV, in both the CeA and medial nucleus of amygdala. In addition, we found that CaMK IV-positive cells were co-localized with NPY in amygdaloid structures of P rats.

CONCLUSIONS

These results suggest that NPY infusion may increase the expression of endogenous NPY in the CeA, which is most likely attributable to an increase in CaMK IV-dependent CREB phosphorylation and this molecular mechanism may be involved in regulating anxiety and alcohol drinking behaviors of P rats.

Neuropeptide Y (NPY) in neuroblastoma: effect on growth and vascularization

Neuroblastomas are pediatric tumors of sympathetic origin, expressing neuronal markers, such as NPY and its receptors. Due to this, neuroblastomas are often associated with elevated plasma levels of NPY, which correlates with poor clinical outcome of the disease. This clinical data corroborates the recent discovery of growth-promoting actions of NPY in neuroblastomas. The peptide has been shown to stimulate proliferation of neuroblastoma cells in an autocrine manner and induce tumor vascularization. Since both processes are mediated by the same Y2 and Y5 receptors, targeting this pathway may be a potential bidirectional therapy for these children's tumors.

Physiology and gene regulation of the brain NPY Y1 receptor

Neuropeptide Y (NPY) is one of the most prominent and abundant neuropeptides in the mammalian brain where it interacts with a family of G-protein coupled receptors, including the Y(1) receptor subtype (Y(1)R). NPY-Y(1)R signalling plays a prominent role in the regulation of several behavioural and physiological functions including feeding behaviour and energy balance, sexual hormone secretion, stress response, emotional behaviour, neuronal excitability and ethanol drinking. Y(1)R expression is regulated by neuronal activity and peripheral hormones. The Y(1)R gene has been isolated from rodents and humans and it contains multiple regulatory elements that may participate in the regulation of its expression. Y(1)R expression in the hypothalamus is modulated by changes in energetic balance induced by a wide variety of conditions (fasting, pregnancy, hyperglycaemic challenge, hypophagia, diet induced obesity). Estrogens up-regulate responsiveness to NPY to stimulate preovulatory GnRH and gonadotropin surges by increasing Y(1)R gene expression both in the hypothalamus and the pituitary. Y(1)R expression is modulated by different kinds of brain insults, such as stress and seizure activity, and alteration in its expression may contribute to antidepressant action. Chronic modulation of GABA(A) receptor function by benzodiazepines or neuroactive steroids also affects Y(1)R expression in the amygdala, suggesting that a functional interaction between the GABA(A) receptor and Y(1)R mediated signalling may contribute to the regulation of emotional behaviour. In this paper, we review the state of the art concerning Y(1)R function and gene expression, including our personal contribution to many of the subjects mentioned above.

Effects of peptides, with emphasis on feeding, pain, and behavior A 5-year (1999-2003) review of publications in Peptides

Novel effects of naturally occurring peptides are continuing to be discovered, and their mechanisms of actions as well as interactions with other substances, organs, and systems have been elucidated. Synthetic analogs may have actions similar or antagonistic to the endogenous peptides, and both the native peptides and analogs have potential as drugs or drug targets. The journal Peptides publishes many leading articles on the structure-activity relationship of peptides as well as outstanding reviews on some families of peptides. Complementary to the reviews, here we extract information from the original papers published during the past five years in Peptides (1999-2003) to summarize the effects of different classes of peptides, their modulation by other chemicals and various pathophysiological states, and the mechanisms by which the effects are exerted. Special attention is given to peptides related to feeding, pain, and other behaviors. By presenting in condensed form the effects of peptides which are essential for systems biology, we hope that this summary of existing knowledge will encourage additional novel research to be presented in Peptides.

What turns CREB on?

The transactivation domain of the cAMP response element-binding protein (CREB) consists of two major domains. The glutamine-rich Q2 domain, which interacts with the general transcription factor TAFII130/135, is sufficient for the recruitment of a functional RNA polymerase II complex and allows basal transcriptional activity. The kinase-inducible domain, however, mediates signal-induced activation of CREB-mediated transcription. It is generally believed that recruitment of the coactivators CREB-binding protein (CBP) and p300 after signal-induced phosphorylation of this domain at serine-133 strongly enhances CREB-dependent transcription. Transcriptional activity of CREB can also be potentiated by phosphoserine-133-independent mechanisms, and not all stimuli that provoke phosphorylation of serine-133 stimulate CREB-dependent transcription. This review presents an overview of the diversity of stimuli that induce CREB phosphorylation at Ser-133, focuses on phosphoserine-133-dependent and -independent mechanisms that affect CREB-mediated transcription, and discusses different models that may explain the discrepancy between CREB Ser-133 phosphorylation and activation of CREB-mediated transcription.

Anxiety and alcohol abuse disorders: a common role for CREB and its target, the neuropeptide Y gene

It has been hypothesized that anxiety disorders play an important role in the initiation and maintenance of alcohol drinking behaviors. However, the molecular mechanisms for the association between anxiety and alcohol abuse are not well understood. Structures of the extended amygdala, particularly the central nucleus of amygdala, are involved in anxiety and in motivational aspects of alcohol drinking behaviors. Here, I propose that cAMP response element-binding protein (CREB) has a role in anxiety and alcohol drinking behaviors. The CREB gene transcription factor regulates the expression of the gene encoding neuropeptide Y (NPY), and decreased concentrations of NPY are implicated in anxiety and alcohol drinking behaviors. Therefore, decreased function of CREB in the central nucleus of the amygdala might regulate anxiety and alcohol intake via decreased expression of NPY, and might provide a common link between anxiety and alcohol abuse disorders. I also suggest that, via CREB, NPY might interact with other CREB target genes, such as the gene encoding brain-derived neurotrophic factor, and that this CREB-mediated interaction might be important in the regulation of anxiety and alcohol drinking behaviors.

Corticotropin-releasing hormone (CRH) expression and protein kinase A mediated CRH receptor signalling in an immortalized hypothalamic cell line

Corticotropin-releasing hormone (CRH) is a 41 amino acid neuropeptide which plays an important role in the stress response in the hypothalamus. We describe the development of an immortalized hypothalamic cell line which expresses CRH. We hypothesized that this cell line would possess the relevant characteristics of parvocellular CRH-expressing neurones such as glucocorticoid receptor (GR) expression and vasopressin (VP) coexpression. For production of hypothalamic cells, embryonic day 19 rat pup hypothalami were dissected and dissociated into tissue culture dishes. They were immortalized by retrovirus-mediated transfer of the SV40 large T antigen gene at 3 days of culture and then screened for expression of CRH following dilution cloning. One cell line was chosen (IVB) which exhibited CRH-like immunoreactivity (CRH-LI) and expressed CRH, VP and CRH1 receptor RNA via the reverse transcriptase-polymerase chain reaction. In addition, the cell line expressed the neuronal marker, microtubule-associated protein-2. We verified that the CRH-LI from IVB cell lysates coeluted with CRH standard via reversed-phase high-performance liquid chromatography (HPLC). Furthermore, oxidation of the lysate converted its HPLC profile to that identical with oxidized CRH standard. In addition, IVB cells exhibited high affinity binding to CRH. Incubation of IVB cells with CRH lead to increases in cAMP levels and protein kinase A activity in a concentration-dependent manner. Incubation of IVB cells with CRH also resulted in increases in phospho-cyclic-AMP response element binding protein (CREB) immunostaining as detected by immunocytochemical analysis. Finally, CRH treatment of IVB cell lines has been linked to CREB-mediated gene expression as determined via the PathDetect CREB trans-reporting system. The characteristics of IVB cells, such as CRH and VP coexpression, GR expression and a biologically active CRH-R1-mediated signalling pathway, suggest that this neuronal cell line may serve as model of parvocellular CRH neurones.