Neuropeptide Y, ubiquitous and elusive

Nicotine-mediated dopamine regulates short neuropeptide F to inhibit brown planthopper feeding behavior in tobacco-rice rotation cropping

BACKGROUND

The tobacco-rice rotation cropping (TRRC) is an ecologically friendly system that can both alleviate soil nicotine pollution and decrease the brown planthopper (BPH, Nilaparvata lugens Stål) fitness on rice. However, few studies on this green and effective rotational cropping system have been reported. In particular, the underlying mechanisms of TRRC on the significant reduction of field pest population at the molecular level is still unknown.

RESULTS

Field investigation showed that BPH population decreased significantly in TRRC than in rice-rice successive cropping (RRSC) field. In addition, the short neuropeptide F (NlsNPF) and its receptor NlA7 of BPH had half-times lower levels in the TRRC field. Behavioral bioassay indicated a 1.93-fold increase in the number of salivary flanges of the dsNlsNPF group, while BPH fitness parameters, such as honeydew, weight gain, and mortality decreased significantly. Dopamine (DA) content in BPH decreased by ~11.1% under the influence of nicotine, and its presence increased the expression levels of NlsNPF and NlA7. Exogenous DA application eliminated the inhibitory effects of nicotine on BPH feeding and restored the fitness levels of its parameters. Independent application of either a mixture of dsNlsNPF with a nanocarrier or nicotine to the normal rice field revealed that the latter could produce better effects in combination with dsRNA.

CONCLUSION

These findings confirmed that DA regulated NlsNPF to inhibit the BPH feeding behavior in TRRC. The results not only provided novel findings on the mechanism of pest-host interactions, but also presented new method for integrated pest management. © 2023 Society of Chemical Industry.

Current views on neuropeptides in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease involving skin barrier dysfunction and immune imbalance. However, the mechanism of AD is not clear completely and may be related to heredity and environment. Neuropeptides are a class of peptides secreted by nerve endings, they may play roles in promoting vasodilation, plasma extravasation, chemotaxis of inflammatory cells and mediating pruritus. Since itching and immune cell infiltration are the main manifestations of atopic dermatitis, to further investigate the impact of neuropeptides on AD, our review summarized the mechanisms of several common neuropeptides in AD and hypothesized that neuropeptides may be the novel potential targets in AD treatment.

Elevated Pentraxin 3 in Obese Adipose Tissue Promotes Adipogenic Differentiation by Activating Neuropeptide Y Signaling

Obesity is accompanied by chronic systemic inflammation characterized by macrophage infiltration of obese tissues, an elevated plasma level of inflammatory substances, and excessive accumulation of lipids. The pro-inflammatory factor pentraxin 3 (PTX3) is also elevated in obese tissues, suggesting its potential role in adipogenesis. We found by analyzing murine preadipocyte 3T3-L1 cells, and human adipocytes derived from mesenchymal stem cells, which locally elevated PTX3 in obese adipose tissue augments adipocyte differentiation and subsequent lipid accumulation. This occurs via the upregulation of adipogenesis-related transcription factors. PTX3 enhanced lipid accumulation in murine 3T3-L1 cells by upregulating the expression of neuropeptide Y (NPY)/NPY receptor (NPYR) expression in preadipocytes. Pharmacological inhibition by NPYR antagonists abolished these effects. NPY also promoted the production of reactive oxygen species (ROS), a known trigger of adipogenesis. NPYR antagonists as well as antioxidant N-acetylcysteine showed anti-adipogenic effects by reducing the ROS levels, indicating that PTX3 mediates adipogenesis through NPY-dependent ROS production. These findings suggest that PTX3 plays a key role in the development of obesity by enhancing adipocyte differentiation and lipid synthesis via NPY/NPYR signaling. These observations provide a mechanistic explanation for the adipogenesis mediated by PTX3.

Appetite-associated responses to central neuropeptide Y injection in quail

The appetite-associated effects of neuropeptide Y (NPY) have been extensively studied in mammalian models. Less knowledge exists for other vertebrate species including birds. The aim of this study was to determine the effects of central injection of NPY on feeding behavior and hypothalamic physiology in 7 day-old Japanese quail (Coturnix japonica). During the light cycle, intracerebroventricular injection of 1.9 pmol, 0.5, and 1.0 nmol doses of NPY did not affect food intake, 0.031 to 0.13 nmol increased food intake, and 2.0 nmol NPY decreased food intake, in comparison to vehicle injection. Multiple doses of NPY stimulated water intake, but when food was not available, water intake was not affected. When injected during the dark cycle, NPY did not influence food intake. NPY-injected chicks had more c-Fos immunoreactive cells in the arcuate nucleus of the hypothalamus (ARC) and greater hypothalamic agouti-related peptide and neuropeptide Y receptors 1 and 2 (NPYR1 and NPYR2, respectively) mRNA than vehicle-injected chicks. Within the ventromedial hypothalamus, NPY-treated chicks expressed less NPYR1 mRNA, within the dorsomedial hypothalamus less NPY mRNA, and in the ARC greater NPYR2 mRNA than vehicle-injected chicks. Lastly, quail injected with NPY increased feeding pecks, escape attempts, and time spent preening, while locomotion, the number of steps, and time spent perching decreased compared to chicks injected with the vehicle. Results demonstrate that NPY stimulates food intake in quail, consistent with mammals and other avian species, but with some unique responses at the molecular level that are not documented in other species.

Neuromodulatory connectivity defines the structure of a behavioral neural network

Neural networks are typically defined by their synaptic connectivity, yet synaptic wiring diagrams often provide limited insight into network function. This is due partly to the importance of non-synaptic communication by neuromodulators, which can dynamically reconfigure circuit activity to alter its output. Here, we systematically map the patterns of neuromodulatory connectivity in a network that governs a developmentally critical behavioral sequence in Drosophila. This sequence, which mediates pupal ecdysis, is governed by the serial release of several key factors, which act both somatically as hormones and within the brain as neuromodulators. By identifying and characterizing the functions of the neuronal targets of these factors, we find that they define hierarchically organized layers of the network controlling the pupal ecdysis sequence: a modular input layer, an intermediate central pattern generating layer, and a motor output layer. Mapping neuromodulatory connections in this system thus defines the functional architecture of the network.

Why do animals behave the way they do? Behavior occurs in response to signals from the environment, such as those indicating food or danger, or signals from the body, such as those indicating hunger or thirst. The nervous system detects these signals and triggers an appropriate response, such as seeking food or fleeing a threat. But because much of the nervous system takes part in generating these responses, it can make it difficult to understand how even simple behaviors come about.

One behavior that has been studied extensively is molting in insects. Molting enables insects to grow and develop, and involves casting off the outer skeleton of the previous developmental stage. To do this, the insect performs a series of repetitive movements, known as an ecdysis sequence. In the fruit fly, the pupal ecdysis sequence consists of three distinct patterns rhythmic abdominal movement. A hormone called ecdysis triggering hormone, or ETH for short, initiates this sequence by triggering the release of two further hormones, Bursicon and CCAP. All three hormones act on the nervous system to coordinate molting behavior, but exactly how they do so is unclear.

Diao et al. have now used genetic tools called Trojan exons to identify the neurons of fruit flies on which these hormones act. Trojan exons are short sequences of DNA that can be inserted into non-coding regions of a target gene to mark or manipulate the cells that express it. When a cell uses its copy of the target gene to make a protein, it also makes the product encoded by the Trojan exon. Using this technique, Diao et al. identified three sets of neurons that produce receptor proteins that recognize the molting hormones. Neurons with ETH receptors start the molting process by activating neurons that make Bursicon and CCAP. Neurons with Bursicon receptors then generate motor rhythms within the nervous system. Finally, neurons with CCAP receptors respond to these rhythms and produce the abdominal movements of the ecdysis sequence.

Many other animal behaviors depend on substances like ETH, Bursicon and CCAP, which act within the brain to change the activity of neurons and circuits. The work of Diao et al. suggests that identifying the sites at which such substances act can help reveal the circuits that govern complex behaviors.

Neuropeptides as Regulators of Behavior in Insects

Neuropeptides are by far the largest and most diverse group of signaling molecules in multicellular organisms. They are ancient molecules important in regulating a multitude of processes. Their small proteinaceous character allowed them to evolve and radiate quickly into numerous different molecules. On average, hundreds of distinct neuropeptides are present in animals, sometimes with unique classes that do not occur in distantly related species. Acting as neurotransmitters, neuromodulators, hormones, or growth factors, they are extremely diverse and are involved in controlling growth, development, ecdysis, digestion, diuresis, and many more physiological processes. Neuropeptides are also crucial in regulating myriad behavioral actions associated with feeding, courtship, sleep, learning and memory, stress, addiction, and social interactions. In general, behavior ensures that an organism can survive in its environment and is defined as any action that can change an organism's relationship to its surroundings. Even though the mode of action of neuropeptides in insects has been vigorously studied, relatively little is known about most neuropeptides and only a few model insects have been investigated. Here, we provide an overview of the roles neuropeptides play in insect behavior. We conclude that multiple neuropeptides need to work in concert to coordinate certain behaviors. Additionally, most neuropeptides studied to date have more than a single function.

Long-Term Over-Expression of Neuropeptide Y in Hypothalamic Paraventricular Nucleus Contributes to Adipose Tissue Insulin Resistance Partly via the Y5 Receptor

Intracerebroventricular injection and overexpression of Neuropeptide Y (NPY) in the paraventricular nucleus (PVN) has been shown to induce obesity and glucose metabolism disorder in rodents; however, the underlying mechanisms are still unclear. The aim of this study was to investigate the mechanism contributing to glucose metabolic disturbance induced by NPY. Recombinant lentiviral NPY vectors were injected into the PVN of rats fed a high fat (HFD) or low-fat diet. 8 weeks later, in vivo intravenous glucose tolerance tests and euglycemic-hyperinsulinemic clamp revealed that insulin resistance of adipose tissue were induced by NPY overexpression with or without HFD. NPY increased food intake, but did not change blood glucose, glycated hemoglobin A1c (HbA1c) or lipid levels. However, NPY decreased the expression of pGSK3β, PI3K p85 and pAKTSer473 in adipose tissue of rats. In vitro, 3T3-L1 adipocytes were treated with NPY, NPY Y1 and Y5 receptor antagonists. Glucose consumption and 2-deoxy-D-[3H] glucose uptake were partly inhibited by NPY, while a decrease in PI3K-AKT pathway signaling and a decreased expression of pGSK3α and pGSK3β were observed. Nevertheless, a Y5 receptor antagonist (L-152,804) reversed the effects of NPY on glucose uptake and consumption. These data suggest that long-term over-expression of NPY in PVN contributes to the establishment of adipose tissue insulin resistance, at least partly via the Y5 Receptor.

Dose-dependent effects of neuropeptide Y on the regulation of preadipocyte proliferation and adipocyte lipid synthesis via the PPARγ pathways

The objective of this study was to investigate the impact of neuropeptide Y (NPY) on preadipocyte proliferation and differentiation. Preadipocytes were incubated with a range of concentrations of NPY (10(-15)M - 10(-7)M). After NPY-induced differentiation, the extent of preadipocyte adipogenesis was evaluated. The expressions levels of related adipocyte markers such as PPARγ, C/EBPα and DLK-1 were examined by real-time PCR (RT-PCR) or western blot analysis. Furthermore, the mitogen-activated protein kinase (MAPK) signaling pathway proteins were also analyzed by western blot. Our results showed that low doses of NPY stimulated preadipocyte viability and proliferation, while high NPY doses inhibited cell viability. At high concentrations of NPY significantly promoted lipid accumulation and increased the size of lipid droplets. DLK-1 mRNA expression was inhibited, but the expression levels of PPARγ and C/EBPα were increased during differentiation with the presence of high concentration of NPY. High-dose NPY also suppressed the phosphorylation of the extracellular signal-regulated kinase (ERK) 1/2 protein. We conclude that NPY has a biphasic effect on preadipocyte proliferation. A high dose inhibits the proliferation of 3T3-L1 cell while promotes adipocyte differentiation, increasing lipid accumulation especially enlarged lipid droplets' size. NPY may lead to a better understanding for drug development to prevent hyperplastic obesity and hypertrophic obesity.

The NPY intergeniculate leaflet projections to the suprachiasmatic nucleus transmit metabolic conditions

The intergeniculate leaflet (IGL) is classically known as the area of the Thalamic Lateral Geniculate Complex providing the suprachiasmatic nucleus (SCN) non-photic information. In the present study we investigated whether this information might be related to the metabolic state of the animal. The following groups of male Wistar rats were used for analysis of neuropeptide Y (NPY) and c-Fos in the IGL and SCN. (1) Fed ad libitum. (2) Fasted for 48 h. (3) Fasted for 48 h followed by refeeding for 3 h. (4) Monosodium glutamate-lesioned and 48 h fasted. (5) Electrolytic lesion in the IGL and 48 h fasted. The results were quantified by optical densitometry. Neuronal tracers were injected in two brain areas that receive metabolic information from the periphery, the arcuate nucleus (ARC) and Nucleus of the Tractus Solitarius to investigate whether there is an anatomical relationship with the IGL. Lesion studies showed the IGL, and not the ARC, as origin of most NPY projections to the SCN. Fasting induced important changes in the NPY expression in the IGL, coinciding with similar changes of NPY/glutamate decarboxylase projections of the IGL to the SCN. These changes revealed that the IGL is involved in the transmission of metabolic information to the SCN. In fasted animals IGL lesion resulted in a significant increase of c-Fos in the SCN as compared to intact fasted animals demonstrating the inhibitory influence of the IGL to the SCN in fasting conditions. When the animal after fasting was refed, an increase of c-Fos in the SCN indicated a removal of this inhibitory input. Together these observations show that in addition to increased inhibitory IGL input during fasting, the negative metabolic condition also results in increased excitatory input to the SCN via other pathways. Consequently the present observations show that at least part of the non-photic input to the SCN, arising from the IGL contains information about metabolic conditions.

A putative morphological substrate of the catecholamine-influenced neuropeptide Y (NPY) release in the human hypothalamus

Neuropeptide Y (NPY) is a 36 amino acid peptide, which among others, plays a pivotal role in stress response. Although previous studies confirmed that NPY release is increased by stress in several species, the exact mechanism of the stress-induced NPY release has not been elucidated yet. In the present study, we examined, with morphological means, the possibility that catecholamines directly influence NPY release in the human hypothalamus. Since the use of electron microscopic techniques is virtually impossible in immunostained human samples due to the long post mortem time, double-label immunohistochemistry was utilised in order to reveal the putative catecholaminergic-NPY associations. The present study is the first to demonstrate juxtapositions between the catecholaminergic, tyrosine hydroxylase (TH)/dopamine-beta hydroxylase (DBH)-immunoreactive (IR) and NPY-IR neural elements in the human hypothalamus. These en passant type associations are most numerous in the infundibular and periventricular areas of the human diencephalon. Here, NPY-IR neurons often form several contacts with catecholaminergic fibre varicosities, without any observable gaps between the contacting elements, suggesting that these juxtapositions may represent functional synapses. The lack of phenylethanolamine N-methyltransferase (PNMT)-NPY juxtapositions and the relatively few observed DBH-NPY associations suggest that the vast majority of the observed TH-NPY juxtapositions represent dopaminergic synapses. Since catecholamines are known to be the crucial components of the stress response, the presence of direct, catecholaminergic (primarily dopaminergic)-NPY-IR synapses may explain the increased NPY release during stress. The released NPY in turn is believed to play an active role in the responses that are directed to maintain the homeostasis during stressful conditions.

Neuropeptide Y receptors in carotid plaques of symptomatic and asymptomatic patients: effect of inflammatory cytokines

AIMS

Cytokines released by the immune cells at the site of plaque milieu induce smooth muscle cell apoptosis to promote plaque instability. But, neuropeptide Y (NPY), a pleotropic factor, may modulate the effects of cytokines in atherosclerotic plaques of patients with carotid stenosis. Our aim was to investigate the relative expression of NPY-Y1, NPY-Y2 and NPY-Y5 receptors on carotid plaque vascular smooth muscle cells (pVSMCs) of symptomatic (S) and asymptomatic (AS) patients and examine the effect of inflammatory cytokines on the expression of NPY receptors, that may attenuate plaque rupture.

METHODS AND RESULTS

In healthy carotid artery, there were significantly increased immunopositivity and increased mRNA transcripts of NPY-Y1 and NPY-Y5 receptors in thin sections and isolated VSMCs, respectively, compared to S and AS plaques. However, the NPY-Y2 expression was higher in S and AS pVSMCs than controls. Stimulation of the cells with TNF-α, IL-12 or IFN-γ (50 ng/ml) decreased mRNA transcripts of NPY-Y1 and NPY-Y5 and increased NPY-Y2 mRNAs in VSMCs of healthy carotid artery. The effect of the cytokines on mRNA transcripts of NPY-Y5 and NPY-Y2 in pVSMCs of S and AS patients was similar to healthy VSMCs, but with variable effect on NPY-Y1.

CONCLUSION

Increased expression of NPY-Y2 receptors in symptomatic pVSMCs than in healthy and asymptomatic subjects suggests a potential role of NPY-Y2 in plaque instability. This is further supported by the pronounced effect of atheroma-associated cytokines to increase NPY-Y2 mRNA transcripts in pVSMCs of patients with carotid stenosis.

Neuropeptides and enzymes are targets for the action of endocrine disrupting chemicals in the vertebrate brain

Endocrine-disrupting chemicals (EDC) are molecules that interfere with endocrine signaling pathways and produce adverse consequences on animal and human physiology, such as infertility or behavioral alterations. Some EDC act through binding to androgen or/and estrogen receptors primarily operating through a genomic mechanism regulating gene expression. This mechanism of action may induce profound developmental adverse effects, and the major targets of the EDC action are the gene products, i.e., mRNAs inducing the synthesis of various peptidic molecules, which include neuropeptides and enzymes related to neurotransmitters syntheses. Available immunohistochemical data on some of the systems that are affected by EDC in lower and higher vertebrates are detailed in this review.

Neuropeptide Y Y5 receptor promotes cell growth through extracellular signal-regulated kinase signaling and cyclic AMP inhibition in a human breast cancer cell line

Overexpression of neuropeptide Y (NPY) and its receptor system has been reported in various types of cancers. NPY Y5 receptor (Y5R) has been implicated in cell growth and angiogenesis. However, the role of Y5R in breast cancer is unknown. To identify the role of Y5R in breast cancer, we screened several breast cancer cell lines to examine the expression of Y5R and its function in breast cancer. All screened cell lines express both Y1 receptor and Y5R except BT-549, which expresses mainly Y5R. Binding studies showed that NPY, Y5R-selective agonist peptide, and Y5R-selective antagonist (CGP71683A) displaced (125)I-PYY binding in BT-549 cell membranes in a dose-dependent manner. The displacement studies revealed the presence of two binding sites in Y5R with IC(50) values of 29 pmol/L and 531 nmol/L. NPY inhibited forskolin-stimulated cyclic AMP accumulation with an IC(50) value of 52 pmol/L. NPY treatment of BT-549 cells induced extracellular signal-regulated kinase phosphorylation but did not alter intracellular calcium. Y5R activation stimulates BT-549 cell growth, which is inhibited by CGP71683A, pertussis toxin, and extracellular signal-regulated kinase blockade. CGP71683A alone induced cell death in a time- and dose-dependent manner in Y5R-expressing cells. The stimulation of MDA MB-231 cell migration by NPY is inhibited by CGP71683A. Together, our results suggest that Y5R plays an important role in cancer cell growth and migration and could be a novel therapeutic target for breast cancer.

Neurobiological constituents of active, passive, and variable coping strategies in rats: integration of regional brain neuropeptide Y levels and cardiovascular responses

Effective coping strategies build resilience against stress-induced pathology. In the current study, young male rats were categorized as active, passive, or variable copers by observing their responses to being gently restrained on their backs (i.e., the back-test). The rats were subsequently exposed to chronic unpredictable stress, which included several ethologically relevant stressors such as predator odors and calls, for approximately three weeks. During this time, the variable copers, defined as rats that demonstrated a variable as opposed to a rigid response to stress, exhibited more seemingly adaptive responsiveness in three successive forced swim tests than the more consistently responding passive and active copers. This behavioral flexibility was accompanied by increased neuropeptide Y-immunoreactivity in the bed nucleus of the stria terminalis (BNST) and the amygdala and increased fos-immunoreactivity in the BNST. Additionally, the alterations in fecal corticosteroid levels and cardiovascular measures (systolic blood pressure and tail blood volume) between baseline and stress conditions differed according to coping strategy. Factor analysis indicates that variable copers were characterized by a distinct cardiovascular and neural response to the stress exposure. These results suggest that this animal coping model may be useful in discerning the adaptive nature of particular response strategies in the face of environmental exigencies.

Neuroprotective effects of neuropeptide Y-Y2 and Y5 receptor agonists in vitro and in vivo

It is generally assumed that neurodegeneration is connected with glutamatergic hyperactivity, and that neuropeptide Y (NPY) inhibits glutamate release. Some earlier studies indicated that NPY may have neuroprotective effect; however, the results obtained so far are still divergent, and the role of different Y receptors remains unclear. Therefore in the presented study we investigated the neuroprotective potential of NPY and its Y2, Y5 or Y1 receptor (R) ligands against the kainate (KA)-induced excitotoxicity in neuronal cultures in vitro, as well as in vivo after intrahippocampal KA injection and also in an ischemic middle cerebral artery occlusion model after intraventricular injection of Y2R agonist. NPY compounds were applicated 30 min, 1, 3 or 6 h after the start of the exposure to KA, or 30 min after the onset of ischemia. Our results indicate the neuroprotective activity of NPY and its Y2R and Y5R ligands against the kainate-induced excitotoxicity in primary cortical and hippocampal cultures. Importantly, NPY was effective when given as late as 6 h, while Y2R or Y5R agonists 3 h, after starting the exposure to KA. In in vitro studies those protective effects were inhibited by the respective receptor antagonists. Neuroprotection was also observed in vivo after intrahippocampal injection of Y2R and Y5R agonists 30 min or 1 h after KA. No protection was found either in vitro or in vivo after the Y1R agonist. The Y2R agonist also showed neuroprotective activity in the ischemic model. The obtained results indicate that neuropeptide Y produces neuroprotective effect via Y2 and Y5 receptors, and that the compounds may be effective after delayed application.

Catecholaminergic systems in stress: structural and molecular genetic approaches

Stressful stimuli evoke complex endocrine, autonomic, and behavioral responses that are extremely variable and specific depending on the type and nature of the stressors. We first provide a short overview of physiology, biochemistry, and molecular genetics of sympatho-adrenomedullary, sympatho-neural, and brain catecholaminergic systems. Important processes of catecholamine biosynthesis, storage, release, secretion, uptake, reuptake, degradation, and transporters in acutely or chronically stressed organisms are described. We emphasize the structural variability of catecholamine systems and the molecular genetics of enzymes involved in biosynthesis and degradation of catecholamines and transporters. Characterization of enzyme gene promoters, transcriptional and posttranscriptional mechanisms, transcription factors, gene expression and protein translation, as well as different phases of stress-activated transcription and quantitative determination of mRNA levels in stressed organisms are discussed. Data from catecholamine enzyme gene knockout mice are shown. Interaction of catecholaminergic systems with other neurotransmitter and hormonal systems are discussed. We describe the effects of homotypic and heterotypic stressors, adaptation and maladaptation of the organism, and the specificity of stressors (physical, emotional, metabolic, etc.) on activation of catecholaminergic systems at all levels from plasma catecholamines to gene expression of catecholamine enzymes. We also discuss cross-adaptation and the effect of novel heterotypic stressors on organisms adapted to long-term monotypic stressors. The extra-adrenal nonneuronal adrenergic system is described. Stress-related central neuronal regulatory circuits and central organization of responses to various stressors are presented with selected examples of regulatory molecular mechanisms. Data summarized here indicate that catecholaminergic systems are activated in different ways following exposure to distinct stressful stimuli.

DPP-IV inhibition enhances the antilipolytic action of NPY in human adipose tissue

CONTEXT

Dipeptidyl peptidase IV (DPP-IV) inactivates the incretin hormone glucagon-like peptide. It can also affect the orexigenic hormone neuropeptide Y (NPY(1-36)) which is truncated by DPP-IV to NPY(3-36), as a consequence NPY's affinity changes from receptor Y1, which mediates the antilipolytic function of NPY, to other NPY receptors. Little is known whether DPP-IV inhibitors for the treatment of type 2 diabetic (T2DM) patients could influence these pathways.

AIMS

To investigate the in vitro effects of NPY with DPP-IV inhibition in isolated abdominal subcutaneous (AbdSc) adipocytes on fat metabolism, and assessment of NPY receptor and DPP-IV expression in adipose tissue (AT).

METHODS

Ex vivo human AT was taken from women undergoing elective surgery (body mass index: 27.5 (mean +/- s.d.) +/- 5 kg/m2, age: 43.7 +/- 10 years, n = 36). Isolated AbdSc adipocytes were treated with human recombinant (rh)NPY (1-100 nM) with and without DPP-IV inhibitor (1 M); glycerol release and tissue distribution of DPP-IV, Y1 and Y5 messenger RNA (mRNA) were measured and compared between lean and obese subjects.

RESULTS AND CONCLUSION

rhNPY reduced glycerol release, an effect that was further enhanced by co-incubation with a DPP-IV inhibitor [control: 224 (mean +/- s.e.) +/- 37 micromol/l; NPY, 100 nM: 161 +/- 27 micromol/l**; NPY 100 nM/DPP-IV inhibitor, 1 M: 127 +/- 14 micromol/l**; **p < 0.01, n = 14]. DPP-IV was expressed in AbdSc AT and omental AT with relative DPP-IV mRNA expression lower in AbdSc AT taken from obese [77 +/- 6 signal units (SU)] vs. lean subjects (186 +/- 29 SU*, n = 10). Y1 was predominantly expressed in fat and present in all fat depots but higher in obese subjects, particularly the AbdSc AT-depot (obese: 1944 +/- 111 SU vs. lean: 711 +/- 112 SU**, n = 10). NPY appears to be regulated by AT-derived DPP-IV. DPP-IV inhibitors augment the antilipolytic effect of NPY in AT. Further studies are required to show whether this explains the lack of weight loss in T2DM patients treated with DPP-IV inhibitors.

Hungry for life: How the arcuate nucleus and neuropeptide Y may play a critical role in mediating the benefits of calorie restriction

Laboratory studies consistently demonstrate extended lifespan in animals on calorie restriction (CR), where total caloric intake is reduced by 10-40% but adequate nutrition is otherwise maintained. CR has been further shown to delay the onset and severity of chronic diseases associated with aging such as cancer, and to extend the functional health span of important faculties like cognition. Less understood are the underlying mechanisms through which CR might act to induce such alterations. One theory postulates that CR's beneficial effects are intimately tied to the neuroendocrine response to low energy availability, of which the arcuate nucleus in the hypothalamus plays a pivotal role. Neuropeptide Y (NPY), a neurotransmitter in the front line of the arcuate response to low energy availability, is the primary hunger signal affected by CR and therefore may be a critical mechanism for lifespan extension.

Chronic stress, combined with a high-fat/high-sugar diet, shifts sympathetic signaling toward neuropeptide Y and leads to obesity and the metabolic syndrome

In response to stress, some people lose while others gain weight. This is believed to be due to either increased beta-adrenergic activation, the body's main fat-burning mechanism, or increased intake of sugar- and fat-rich "comfort foods." A high-fat, high-sugar (HFS) diet alone, however, cannot account for the epidemic of obesity, and chronic stress alone tends to lower adiposity in mice. Here we discuss how chronic stress, when combined with an HFS diet, leads to abdominal obesity by releasing a sympathetic neurotransmitter, neuropeptide Y (NPY), directly into the adipose tissue. In vitro, when "stressed" with dexamethasone, sympathetic neurons shift toward expressing more NPY, which stimulates endothelial cell (angiogenesis) and preadipocyte proliferation, differentiation, and lipid-filling (adipogenesis) by activating the same NPY-Y2 receptors (Y2Rs). In vivo, chronic stress, consisting of cold water or aggression in HFS-fed mice, stimulates the release of NPY and the expression of Y2Rs in visceral fat, increasing its growth by 50% in 2 weeks. After 3 months, this results in metabolic syndrome-like symptoms with abdominal obesity, inflammation, hyperlipidemia, hyperinsulinemia, glucose intolerance, hepatic steatosis, and hypertension. Remarkably, local intra-fat Y2R inhibition pharmacologically or via adenoviral Y2R knock-down reverses or prevents fat accumulation and metabolic complications. These studies demonstrated for the first time that chronic stress, via the NPY-Y2R pathway, amplifies and accelerates diet-induced obesity and the metabolic syndrome. Our findings also suggest the use of local administration of Y2R antagonists for treatment of obesity and NPY-Y2 agonists for fat augmentation in other clinical applications.

The effects of NOS2 gene deletion on mice expressing mutated human AbetaPP

Nitric oxide synthase 2 (NOS2) and its gene product, inducible NOS (iNOS) play an important role in neuroinflammation by generating nitric oxide (NO), a critical signaling and redox factor in the brain. Although NO is associated with tissue damage, it can also promote cell survival. We hypothesize that during long-term exposure to amyloid-beta (Abeta) in Alzheimer's disease (AD), NO levels fall in the brain to a threshold at which the protective effects of NO cannot be sustained, promoting Abeta mediated damage. Two new mouse models of AD have been developed that utilize this concept of NO's action. These mice express human amyloid-beta protein precursor (AbetaPP) mutations that generate Abeta peptides on a mouse NOS2 knockout background. The APP/NOS2(-/-) bigenic mice progress from Abeta production and amyloid deposition to hyperphosphorylated normal mouse tau at AD-associated epitopes, aggregation and redistribution of tau to somatodendritic regions of neurons and significant neuronal loss including loss of interneurons. This AD-like pathology is accompanied by robust behavioral changes. As APP/NOS2(-/-) bigenic mice more fully model the human AD disease pathology, they may serve as a tool to better understand disease progression in AD and the role of NO in altering chronic neurological disease processes.

Central neural and endocrine mechanisms of non-exercise activity thermogenesis and their potential impact on obesity

The rise in obesity is associated with a decline in the amount of physical activity in which people engage. The energy expended through everyday non-exercise activity, called non-exercise activity thermogenesis (NEAT), has a considerable potential impact on energy balance and weight gain. Comparatively little attention has been paid to the central mechanisms of energy expenditure and how decreases in NEAT might contribute to obesity. In this review, we first examine the sensory and endocrine mechanisms through which energy availability and energy balance are detected that may influence NEAT. Second, we describe the neural pathways that integrate these signals. Lastly, we consider the effector mechanisms that modulate NEAT through the alteration of activity levels as well as through changes in the energy efficiency of movement. Systems that regulate NEAT according to energy balance may be linked to neural circuits that modulate sleep, addiction and the stress response. The neural and endocrine systems that control NEAT are potential targets for the treatment of obesity.

Secretion of neuropeptide Y in human adipose tissue and its role in maintenance of adipose tissue mass

NPY is an important central orexigenic hormone, but little is known about its peripheral actions in human adipose tissue (AT) or its potential paracrine effects. Our objective was to examine NPY's role in AT, specifically addressing NPY protein expression, the effect of NPY on adipokine secretion, and the influence of insulin and rosiglitazone (RSG) on adipocyte-derived NPY in vitro. Ex vivo human AT was obtained from women undergoing elective surgery [age: 42.7 +/- 1.5 yr (mean +/- SE), BMI: 26.2 +/- 0.7 kg/m(2); n = 38]. Western blot analysis was used to determine NPY protein expression in AT depots. Abdominal subcutaneous (AbSc) adipocytes were isolated and treated with recombinant (rh) NPY, insulin, and RSG. NPY and adipokine levels were measured by ELISA. Our results were that NPY was localized in human AT and adipocytes and confirmed by immunohistochemistry. Depot-specific NPY expression was noted as highest in AbSc AT (1.87 +/- 0.23 ODU) compared with omental (Om; 1.03 +/- 0.15 ODU, P = 0.029) or thigh AT (Th; 1.0 +/- 0.29 ODU, P = 0.035). Insulin increased NPY secretion (control: 0.22 +/- 0.024 ng/ml; 1 nM insulin: 0.26 +/- 0.05 ng/ml; 100 nM insulin: 0.29 +/- 0.04 ng/ml; 1,000 nM insulin: 0.3 +/- 0.04 ng/ml; P < 0.05, n = 13), but cotreatment of RSG (10 nM) with insulin (100 nM) had no effect on NPY secretion. Furthermore, adipocyte treatment with rh-NPY downregulated leptin secretion (control: 6.99 +/- 0.89 ng/ml; 1 nmol/l rh-NPY: 4.4 +/- 0.64 ng/ml; 10 nmol/l rh-NPY: 4.3 +/- 0.61 ng/ml, 100 nmol/l rh-NPY: 4.2 +/- 0.67 ng/ml; P < 0.05, n = 10) but had no effect on adiponectin or TNF-alpha secretion. We conclude that NPY is expressed and secreted by human adipocytes. NPY secretion is stimulated by insulin, but this increment was limited by cotreatment with RSG. NPY's antilipolytic action may promote an increase in adipocyte size in hyperinsulinemic conditions. Adipose-derived NPY mediates reduction of leptin secretion and may have implications for central feedback of adiposity signals.

Prenatal stress in the rat results in increased blood pressure responsiveness to stress and enhanced arterial reactivity to neuropeptide Y in adulthood

We have shown previously that stress in the pregnant rat leads to a heightened cardiovascular response to restraint in adult offspring. The present study was undertaken to explore further the persistent cardiovascular effects of prenatal stress, with a focus on peripheral vascular function. Sprague-Dawley female rats were exposed to restraint/bright light three times daily in the last week of pregnancy. Litters from stressed and control females were cross-fostered to control dams to eliminate possible effects of maternal stress on nursing behaviour. At 120 days, offspring cardiovascular variables were measured by radiotelemetry. Reactivity of mesenteric small arteries was assessed by myography, and responses to electrical field stimulation determined. Resting cardiovascular parameters in prenatally stressed (PS) offspring were similar to controls but PS rats showed a greater increase in systolic blood pressure following restraint stress (P<0.05). Recovery was also prolonged in PS animals compared with controls and was of longer duration in PS females than in PS males (P<0.05). Adult PS females, but not males, also had elevated basal plasma corticosterone levels in comparison with controls (P<0.05). Vascular reactivity to neuropeptide Y (P<0.05) and electrical field stimulation (P<0.05) in mesenteric arteries was also significantly increased in PS animals. Vascular responses to adrenergic agonists as well as endothelial dilator function did not differ between PS and controls. We conclude that prenatal stress during late gestation has long-lasting effects on cardiovascular responsiveness and vascular reactivity to neuropeptide Y in the offspring.

Effects of neuropeptide Y2 receptor blockade on ventricular arrhythmias in rats with acute myocardial infarction

Excessive sympathetic activity is believed to be the key arrhythmogenic factor both in the setting of acute myocardial infarction and during chronic heart failure. The aim of this study was to evaluate the effect of neuropeptide Y2 blockade on malignant ventricular arrhythmias in rats with acute myocardial infarction. Vagotonic dose-finding study for neuropeptide Y2 receptor antagonist, (S)-N2-[2-[4-[(R,S)-5,11-dihydro-6(6h)-oxodibenz[b,e]azepin-11-yl]-1-piperazinyl]-2-oxoethyl] cylopentyl] acetyl]-N-[2-[1,2-dihydro-3,5 (4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamid (AR-H05359) was conducted in guinea pigs (n=50) and rats (n=3). Induction of postinfarction arrhythmias was conducted in Sprague-Dawley rats that were randomized into 3 groups. Neuropeptide Y2 antagonist treated rats (n=7), placebo group (n=10) and amiodarone treated rats (n=8). Myocardial infarction was induced by ligation of the left coronary artery. Computerized telemetric ECG tracings were obtained continuously before induction of myocardial infarction and up to 120 min postinfarction. Occurrence of ventricular arrhythmias was analyzed according to a 10-point arrhythmia score. There was no difference in the arrhythmia scores between the neuropeptide Y2 and the saline group. The amiodarone treated animals had lower score compared to the neuropeptide Y2 and the placebo group (p<0.05). The blockade of receptors does not reduce ventricular arrhythmias in the rats with acute myocardial infarction. Further studies are needed to evaluate whether increasing vagal tonus during sympathetic activation may be valuable anti-arrhythmic strategy to prevent sudden death in patients with myocardial infarction and heart failure.

Role of brain neuroactive steroids in the functional interplay between the GABA(A) and the NPY-Y1 receptor mediated signals in the amygdala

Various lines of evidence suggest a functional interaction between GABA(A) and Neuropeptide Y (NPY)-Y(1) receptor (Y(1)R) mediated transmissions in various brain regions, which can be important in the regulation of sedation, feeding, anxious behaviour and neuronal excitability. By using a transgenic mouse model carrying the murine Y(1)R gene promoter fused to the lacZ reporter gene (Y(1)R/LacZ mice), we showed that prolonged pharmacologically or physiologically induced changes in the cerebrocortical concentrations of the neuroactive steroids 3alpha-hydroxy-5alpha-pregnan- 20-one (3alpha,5alpha TH PROG) and tetrahydrodeoxycorticosterone (3alpha,5alpha TH DOC) increases Y(1)R/LacZ transgene expression in the central and medial amygdala, an effect similar to that induced by long-term treatment with positive modulators of the GABA(A) receptor complex (diazepam or abecarnil). We also demonstrated that fluctuations in the cerebrocortical concentrations of 3alpha,5alpha-TH PROG and 3alpha,5alpha TH DOC during voluntary ethanol consumption and ethanol withdrawal induces a marked increase in Y(1)R gene expression that becomes apparent 48 h after withdrawal. These data provide evidence that neuroactive steroids may play an important role in the functional interaction between the GABA(A) receptor and NPY-Y(1)R mediated pathways in the amygdala, which might represent an important regulatory mechanism for modulation of several functions, including ethanol withdrawal.

The effects of social isolation on neuropeptide Y levels, exploratory and anxiety-related behaviors in rats

NPY is one of the most abundantly expressed peptides within the CNS, and has been previously demonstrated to be altered in several animal models of depression, as well as to be differentially regulated by acute and repeated stress. The effect of social deprivation, through isolation housing, on brain NPY concentrations in adult rats has not been previously investigated. The effects of 12 weeks of social isolation, in adult rats, on anxiety-related behaviors and central concentrations of NPY in: hypothalamus, amygdala, caudate-putamen, hippocampus, and frontal cortex were evaluated. Single housed animals spent significantly more time on the open arms of the elevated plus maze and in the central area of the open field as compared to pair housed controls. These data are most likely indicative of enhanced exploration and novelty seeking. Concentrations of neuropeptide Y were increased in the caudate-putamen of the single housed subjects. NPY levels in caudate/putamen and hypothalamus were also significantly correlated with time spent in the open arms of the elevated plus maze. These data suggest that chronic social isolation, in these adult Wistar rats, did not increase anxiety but produced enhanced exploration in tests of anxiety, an effect that was associated with NPY concentrations in the striatum and hypothalamus.

Chronic Stress Induces Rapid Occlusion of Angioplasty-Injured Rat Carotid Artery by Activating Neuropeptide Y and Its Y1 Receptors

OBJECTIVE

We reported previously that neuropeptide Y (NPY) induces an atherosclerotic-like lesion that is significantly reduced by NPY-Y1 and NPY-Y5 receptor (R) inhibitors. Because antagonists also inhibit neointima induced by angioplasty alone, we now test whether stress-induced endogenous NPY release mimic these changes.

METHODS AND RESULTS

Rats were nonstressed or stressed (4 degrees C water; 2 hours per day for 14 days) starting immediately before and continuing after carotid artery angioplasty. Stress acutely and chronically increased blood pressure and doubled plasma NPY levels. After 14 days, angioplasty-induced neointima was markedly greater in stressed (than nonstressed) rats, in which most of the vessels became occluded with an atherosclerotic-like lesion containing macrophages, lipids, thrombus, and microvessels that was similar but more inflammatory than the injury in the NPY-treated vessels. Fourteen days after angioplasty combined with stress or NPY, Y1R and Y5R (mRNA and protein) became upregulated in areas of neointima, microvessels, and macrophages in injured carotid arteries. Stress- and NPY-induced changes were completely prevented by a selective Y1R antagonist (0.02 micromol/kg per minute for 14 days), whereas neointima induced by angioplasty alone was reduced by 60%.

CONCLUSIONS

Because of sympathetic NPY release, stress may be a less-than-appreciated risk factor for restenosis/atherosclerosis, and Y1R antagonists a potential therapy for these conditions.

Introduction to the reviews on neuropeptide Y

Neuropeptide Y (NPY) was first reported as an abundant peptide in brain tissue in 1982. Shortly thereafter, NPY was found to be a member of a peptide family consisting of the endocrine peptides pancreatic polypeptide (PP) and peptide YY (PYY). These peptides exert most of their biological effects through five G-protein coupled receptors termed Y1, Y2, Y4, Y5 and y6 that mediate either inhibition adenylate cyclase or increases in intracellular calcium. Since the discovery of NPY, a robust a body of literature has developed around the potential functions of this peptide. While initial findings identified NPY is an important contributor to the regulation of feeding, body weight and blood pressure, more recent work as revealed more subtle functions of this peptide and its potential role in affective disorders, bone formation and cravings. The accompanying twelve reviews detail important developments in our understanding of the functional role of NPY.