Multiple neuropeptide Y receptors are involved in cardiovascular regulation. Peripheral and central mechanisms

Effects of Nifedipine on Renal and Cardiovascular Responses to Neuropeptide Y in Anesthetized Rats

Neuropeptide Y (NPY) acts via multiple receptor subtypes termed Y₁, Y₂ and Y₅. While Y₁ receptor-mediated effects, e.g., in the vasculature, are often sensitive to inhibitors of L-type Ca²⁺ channels such as nifedipine, little is known about the role of such channels in Y₅-mediated effects such as diuresis and natriuresis. Therefore, we explored whether nifedipine affects NPY-induced diuresis and natriuresis. After pre-treatment with nifedipine or vehicle, anesthetized rats received infusions or bolus injections of NPY. Infusion NPY (1 µg/kg/min) increased diuresis and natriuresis, and this was attenuated by intraperitoneal injection of nifedipine (3 µg/kg). Concomitant decreases in heart rate and reductions of renal blood flow were not attenuated by nifedipine. Bolus injections of NPY (0.3, 1, 3, 10 and 30 μg/kg) dose-dependently increased mean arterial pressure and renovascular vascular resistance; only the higher dose of nifedipine (100 μg/kg/min i.v.) moderately inhibited these effects. We conclude that Y₅-mediated diuresis and natriuresis are more sensitive to inhibition by nifedipine than Y₁-mediated renovascular effects. Whether this reflects a general sensitivity of Y₅ receptor-mediated responses or is specific for diuresis and natriuresis remains to be investigated.

Molecular Mechanisms and Aspects on the Role of Neuropeptide Y as a Zn2+ and Cu2+ Chelator

The concept of metal chelation is based on simple coordination chemistry. The development of an ideal metal chelator that completely and selectively removes toxic metals from a specific metal binding site in proteins is required to prevent and or inhibit a variety of diseases, among them neurodegenerative diseases. This work examines neuropeptide Y (NPY) as a Zn²⁺ and Cu²⁺ chelator agent. NPY is a natural peptide that is produced in the human body; therefore, it is not a toxic agent and the complex that it forms is not toxic as well. Our simulations reveal that NPY has an efficient Zn²⁺ chelation activity but is less effective in chelating Cu²⁺. Moreover, while NPY demonstrates several conformations, the metal chelation occurs more efficiently in its native structure. Beyond the exploration of the activity of NPY as a Zn²⁺ and Cu²⁺ chelator agent, this work provides an insight into the molecular mechanisms of the chelation of these metals at the molecular level. The outcomes from this work may guide future experimental studies to examine NPY in metal chelation therapy for neurodegenerative diseases.

Effect of carvedilol versus nebivolol on insulin resistance among non-diabetic, non-ischemic cardiomyopathy with heart failure

Background

Although B-blockers provide unequivocal benefits in heart failure (HF) management, some B-blockers worsen insulin resistance. It will be a promising strategy to recruit such a B blocker that did not worsen or can even improve insulin resistance (IR).

So, this study aimed to assess the effect of two of the third-generation B-blockers (carvedilol versus nebivolol) on insulin sensitivity state in non-diabetic patients with non-ischemic cardiomyopathy with heart failure.

Results

Out of 43 patients enrolled, 58.1% represented the carvedilol group while 41.9% represented the nebivolol group. Nebivolol improves insulin resistance-related variables (fasting glucose, fasting insulin, and HOMA-IR; P < 0.001, 0.01, and 0.01 respectively). The percentage of change at homeostasis model of assessment (HOMA-IR), indicative of insulin sensitivity status, between baseline versus at 3-months follow-up level of intra-group comparison was increased by 4.58% in the carvedilol arm whereas it was decreased by 11.67% in the nebivolol arm, and the difference on the intragroup level of comparison was significant (P < 0.001 and 0.01 respectively).

Conclusion

Nebivolol improves insulin resistance-related variables .Nebivolol may be recommended as the B blocker of the first choice for those with non-ischemic cardiomyopathy heart failure with evident insulin resistance; however, larger scaled prospective multicenter randomized trials are needed for confirming our favorable results.

Neuropeptide Y3-36 incorporated into PVAX nanoparticle improves angiogenesis in a murine model of myocardial ischemia

Neuropeptide-Y (NPY) leads to angiogenesis and remodeling of the ischemic myocardium. The objective of this study is to assess the therapeutic potential of NPY in a model of acute myocardial ischemia using a nanoparticles delivery system targeted to tissue with oxidative stress. NPY_3-36 was loaded onto copolyoxalate containing vanillyl alcohol (PVAX) using a double emulsification strategy. Adult C57BL/J6 mice (n = 49) were randomly divided into PVAX-NPY_3-36 (n = 22), Vehicle (Saline) (n = 16), and Sham (n = 11) groups. The ischemia to left anterior descending artery was induced in PVAX-NPY_3-36 or vehicle groups. The tissue was collected at the end of two weeks after assessing the functional and echocardiographic data. There was a significant decrease in infarction size and mortality in PVAX-NPY_3-36 group compared to the Vehicle group (P = 0.01 and P = 0.05). On echocardiography, there was significant improvement in contractility and diastolic parameters (P = 0.01). On pressure-volume loop there was significant increase in stroke volume (P = 0.01), cardiac output (P = 0.01) and ventricular stroke work (P = 0.01) in the PVAX-NPY_3-36 group. On Western blot analysis, there was a significant increase in pro-angiogenic factors Ang-1, TGF-β, PDGF- β and its receptors and VEGF in the ischemic tissue treated with PVAX-NPY_3-36 as compared to Vehicle ischemic tissue (P = 0.01, P = 0.0003, and P < 0.05 respectively). It may be possible to have targeted delivery of labile neurotransmitters NPY_3-36 to the ischemic myocardium using nanoparticle PVAX and achieving angiogenesis and significant functional improvement.

Deletion of Neuropeptide Y Attenuates Cardiac Dysfunction and Apoptosis During Acute Myocardial Infarction

Increasing neuropeptide Y (NPY) has been shown to be a risk factor for cardiovascular diseases. However, its role and mechanism in myocardial infarction (MI) have not yet been fully understood. H9c2 cells and neonatal rat ventricular myocytes with loss of function of NPY and rats with global knockout were used in this study. MI model of rats was induced by the ligation of left coronary artery, and the extent of MI was analyzed through echocardiographic, pathological, and molecular analyses. Our data demonstrated that NPY expression was significantly increased in MI rats and hypoxia/hydrogen peroxide (H₂O₂)-treated cardiomyocytes. At the same time, NPY-knockout rats exhibited a remarkable decrease in infarct size, serum lactate dehydrogenase activity, cardiomyocyte apoptosis, and caspase-3 expression and activity and a strong improvement in heart contractile function compared with MI rats. Meanwhile, NPY small interfering RNA (siRNA) inhibited the cell apoptosis in H₂O₂-treated H9c2 cells and hypoxia-treated neonatal rat ventricular myocytes. NPY deletion increased miR-499 expression and decreased FoxO4 expression in MI in vivo and in vitro. Moreover, NPY type 1 receptor antagonist BIBO3304 can reverse miR-499 decrease and FoxO4 increase in H₂O₂-induced cardiomyocytes. NPY siRNA inhibited cell apoptosis in H₂O₂-treated H9c2 cells that were reversed by miR-499 inhibitor. Additionally, FoxO4 was validated as the direct target of miR-499. Moreover, BIBO3304 and FoxO4 siRNA significantly increased the cell activity, inhibited the cell apoptosis, and decreased caspase-3 expression and activity in H₂O₂-treated cardiomyocytes that NPY presented the opposite effect. Collectively, deletion of NPY reduced myocardial ischemia, improved cardiac function, and inhibited cardiomyocyte apoptosis by NPY type 1 receptor–miR-499–FoxO4 axis, which provides a new treatment for MI.

The Role of Neuropeptide Y in Cardiovascular Health and Disease

Neuropeptide Y (NPY) is an abundant sympathetic co-transmitter, widely found in the central and peripheral nervous systems and with diverse roles in multiple physiological processes. In the cardiovascular system it is found in neurons supplying the vasculature, cardiomyocytes and endocardium, and is involved in physiological processes including vasoconstriction, cardiac remodeling, and angiogenesis. It is increasingly also implicated in cardiovascular disease pathogenesis, including hypertension, atherosclerosis, ischemia/infarction, arrhythmia, and heart failure. This review will focus on the physiological and pathogenic role of NPY in the cardiovascular system. After summarizing the NPY receptors which predominantly mediate cardiovascular actions, along with their signaling pathways, individual disease processes will be considered. A thorough understanding of these roles may allow therapeutic targeting of NPY and its receptors.

Peptide YY (3-36) modulates intracellular calcium through activation of the phosphatidylinositol pathway in hippocampal neurons

Peptide YY (PYY) belongs to the neuropeptide Y (NPY) family, which also includes the pancreatic polypeptide (PP) and NPY. PYY is secreted by the intestinal L cells, being present in the blood stream in two active forms capable of crossing the blood brain barrier, PYY (1-36) and its cleavage product, PYY (3-36). PYY is a selective agonist for the Y2 receptor (Y2R) and these receptors are abundant in the hippocampus. Here we investigated the mechanisms by which PYY (3-36) regulates intracellular Ca²⁺ concentrations ([Ca²⁺]_i) in hippocampal neurons by employing a calcium imaging technique in hippocampal cultures. Alterations in [Ca²⁺]_i were detected by changes in the Fluo-4 AM reagent emission. PYY (3-36) significantly increased [Ca²⁺] from the concentration of 10^-11M as compared to the controls (infusion of HEPES-buffered solution (HBS) solution alone). The PYY (3-36)-increase in [Ca²⁺]_i remained unchanged even in Ca²⁺-free extracellular solutions. Sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase pump (SERCA pump) inhibition partially prevent the PYY (3-36)-increase of [Ca²⁺]_i and inositol 1,4,5-triphosphate receptor (IP3R) inhibition also decreased the PYY (3-36)-increase of [Ca²⁺]_i. Taken together, our data strongly suggest that PYY (3-36) mobilizes calcium from the neuronal endoplasmic reticulum (ER) stores towards the cytoplasm. Next, we showed that PYY (3-36) inhibited high K⁺-induced increases of [Ca²⁺]_i, suggesting that PYY (3-36) could also act by activating G-protein coupled inwardly rectifying potassium K⁺ channels. Finally, the co-infusion of the Y2 receptor (Y2R) antagonist BIIE0246 with PYY (3-36) abolished the [Ca²⁺]_i increase induced by the peptide, suggesting that PYY (3-36)-induced [Ca²⁺]_i increase in hippocampal neurons occurs via Y2Rs.

Elevated levels of neuropeptide Y in preeclampsia: A pilot study implicating a role for stress in pathogenesis of the disease

OBJECTIVE

To determine if preeclampsia (PE) is associated with dysregulation of the neuropeptide Y (NPY) system.

METHODS

The study enrolled 114 subjects either with normal pregnancy (NP) or with PE. Systolic blood pressure (SBP) was collected from patients using a standard sphygmomanometer. The PE patients were divided into two groups based on the gestational age (GA) at delivery - placental PE (PLPE, GA <34 weeks) or maternal PE (MTPE, GA ≥34 weeks). NPY was measured in platelet rich plasma (PRP), platelet poor plasma (PPP) and in the serum of NP and PE patients utilizing radioimmunoassay. Serum levels of soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) were measured in NP and PE subjects by ELISA.

RESULTS

SBP was higher in PE compared to NP. Circulating NPY in serum and PRP, as well as NPY content per 100,000 platelets, but not its concentrations in PPP, were elevated in PE, as compared to NP. The highest NPY concentrations were observed in sera and PRP of patients with MTPE. PE patients had also elevated levels of sFlt-1, as compared to NP, although no difference between PLPE and MTPL groups were observed. There was no increase in P1GF in PE patients.

CONCLUSION

Systemic NPY is elevated in PE patients, as compared to NP. This increase is observed in blood fractions containing platelets, suggesting accumulation of the peptide in these cells. NPY concentrations are particularly high in patients with MTPE, underlying differences in etiology between PLPE and MTPE. Our study implicates NPY as a potential target in antihypertensive therapies for PE patients.

Over-expression of either MECP2_e1 or MECP2_e2 in neuronally differentiated cells results in different patterns of gene expression

Mutations in MECP2 are responsible for the majority of Rett syndrome cases. MECP2 is a regulator of transcription, and has two isoforms, MECP2_e1 and MECP2_e2. There is accumulating evidence that MECP2_e1 is the etiologically relevant variant for Rett. In this study we aim to detect genes that are differentially transcribed in neuronal cells over-expressing either of these two MECP2 isoforms. The human neuroblastoma cell line SK-N-SH was stably infected by lentiviral vectors over-expressing MECP2_e1, MECP2_e2, or eGFP, and were then differentiated into neurons. The same lentiviral constructs were also used to infect mouse Mecp2 knockout (Mecp2^tm1.1Bird) fibroblasts. RNA from these cells was used for microarray gene expression analysis. For the human neuronal cells, ∼800 genes showed >three-fold change in expression level with the MECP2_e1 construct, and ∼230 with MECP2_e2 (unpaired t-test, uncorrected p value <0.05). We used quantitative RT-PCR to verify microarray results for 41 of these genes. We found significant up-regulation of several genes resulting from over-expression of MECP2_e1 including SRPX2, NAV3, NPY1R, SYN3, and SEMA3D. DOCK8 was shown via microarray and qRT-PCR to be upregulated in both SK-N-SH cells and mouse fibroblasts. Both isoforms up-regulated GABRA2, KCNA1, FOXG1 and FOXP2. Down-regulation of expression in the presence of MECP2_e1 was seen with UNC5C and RPH3A. Understanding the biology of these differentially transcribed genes and their role in neurodevelopment may help us to understand the relative functions of the two MECP2 isoforms, and ultimately develop a better understanding of RTT etiology and determine the clinical relevance of isoform-specific mutations.

Neuropeptide Y receptors: ligand binding and trafficking suggest novel approaches in drug development

NPY, PYY and PP constitute the so-called NPY hormone family, which exert its biological functions in humans through YRs (Y₁, Y₂, Y₄ and Y₅). Systematic modulation of YR function became important as this multireceptor/multiligand system is known to mediate various essential physiological key functions and is involved in a variety of major human diseases such as epilepsy, obesity and cancer. As several YRs have been found to be overexpressed on different types of malignant tumors they emerge as promising target in modern drug development. Here, we summarize the current understanding of YRs function and the molecular mechanisms of ligand binding and trafficking. We further address recent advances in YR-based drug design, the development of promising future drug candidates and novel approaches in YR-targeted tumor diagnostics and therapy opportunities.

Design, synthesis and SAR of a novel series of benzimidazoles as potent NPY Y5 antagonists

A novel class of benzimidazole NPY Y5 receptor antagonists was prepared exploiting a privileged spirocarbamate moiety. The structure-activity relationship of this series and efforts to achieve a profile suitable for further development and an appropriate pharmacokinetic profile in rat are described. Optimisation led to the identification of the brain penetrant, orally bioavailable Y5 antagonist 9b which significantly inhibited the food intake induced by a Y5 selective agonist with a minimal effective dose of 30mg/kg po.

Neuropeptide Y and alpha-melanocyte-stimulating hormone: interaction in obesity and possible role in the development of hypertension

AIM

Obesity and hypertension frequently coexist and both represent important risk factors for cardiovascular disease. The mechanisms implicated in the regulation of food intake have not been completely elucidated. Recent data suggests that peripheral and central neuropeptides play an important role in the maintenance of energy balance. More specifically, leptin, neuropeptide Y (NPY) and alpha-melanocyte-stimulating hormone (a-MSH) appear to be implicated in the pathogenesis of obesity and also contribute to the development of hypertension in obesity.

METHODS

Analysis of the pertinent bibliography published in PubMed database.

RESULTS

Leptin is produced in the adipose tissue directly correlated with fat tissue mass. Leptin acts on two distinct neural populations in the hypothalamus: the first expresses the orexigenic peptides NPY and agouti-related protein (AgRP), the second pro-opiomelanocortin (POMC). The activation of POMC neurons increases the production of the anorexigenic hormone a-MSH and inhibits the release of NPY and AgRP. In addition, the hypothalamus integrates the neuroendocrine systems with the autonomic nervous system and controls the activity of the latter. Stimulation of hypothalamic nuclei elicits sympathetic responses including blood pressure elevation. Both NPY and a-MSH appears to be implicated in the hypothalamic regulation of sympathetic nervous system (SNS) activity.

CONCLUSION

Alterations in leptin, NPY and a-MSH are frequently observed in obesity and might stimulate SNS activity, contributing to the development of hypertension in obese patients. These neuropeptides might provide a pathophysiologic link between excess weight and hypertension. However, more research is needed before the pharmacologic manipulation of these complex neuroendocrine systems can be applied in the treatment of obesity and hypertension.

Exposure to acute physical and psychological stress alters the response of rat macrophages to corticosterone, neuropeptide Y and beta-endorphin

The objective of the present study was to investigate the effect of acute exposure to electric tail shock stress (ES) and a stress witnessing procedure (SW), as models for physical and psychological stress paradigms, respectively on adherence, phagocytosis and hydrogen peroxide (H(2)O(2)) release from rat peritoneal macrophages. In addition, we studied the in vitro effects of corticosterone (CORT), neuropeptide Y (NPY) and beta-endorphin (BE) on adherence, phagocytosis and H(2)O(2) release from macrophages isolated from control rats and from rats that had been exposed to ES or SW procedures 24 h earlier. ES and SW comparably diminished phagocytosis and H(2)O(2) release, but did not influence macrophage adherence. In vitro treatment with CORT and NPY notably suppressed phagocytosis and potentiated H(2)O(2) release from macrophages. BE suppressed both phagocytosis and H(2)O(2) release from macrophages. Previous exposure to ES and SW altered the responsiveness of the isolated macrophages to their in vitro treatment with mediators of stress, making the cells less sensitive to the influence of CORT and NPY and to a lesser extent to BE. It could be concluded that changes in the local macrophage milieu induced by ES and SW 24 h earlier modify macrophage responses to subsequent in vitro exposure to the stress mimics, CORT, NPY and BE.

Central control of atrio-ventricular conduction and left ventricular contractility in the cat heart: Synaptic interactions of vagal preganglionic neurons in the nucleus ambiguus with neuropeptide Y-immunoreactive nerve terminals

In the cat, vagal postganglionic controls of heart rate, atrio-ventricular (AV) conduction and left ventricular contractility are mediated by three separate intrinsic cardiac ganglia, the sinoatrial (SA), AV and cranioventricular (CV) ganglia, respectively. The vagal preganglionic neurons (VPNs) that project to these ganglia are located in the ventrolateral nucleus ambiguus (NA-VL). We have previously shown that the VPNs projecting to the SA, AV and CV ganglia are distinct from one another. We have also demonstrated that neuropeptide Y-immunoreactive (NPY-IR) axon terminals synapse upon VPNs projecting to the SA ganglion. In the present study, we test the hypothesis that those VPNs projecting to the AV ganglion (negative dromotropic VPNs) and those projecting to the CV ganglion (negative inotropic VPNs) are innervated by NPY-IR terminals in NA-VL. A retrograde tracer was injected into the AV or CV ganglion of the cat, and the brains subsequently processed for visualization of tracer and the immunocytochemical visualization of NPY by dual labeling electron-microscopic methods. We observed that 11+/-5% of all axodendritic synapses and 8+/-6% of all axosomatic synapses upon negative inotropic VPNs were NPY-IR. Furthermore, 19+/-14% of all axodendritic synapses upon negative dromotropic VPNs were NPY-IR. A few NPY-IR axosomatic synapses upon negative dromotropic neurons were also observed. NPY-IR terminals in NA-VL occasionally formed axosomatic synapses with NPY-IR neurons and axoaxonic synapses with unlabeled terminals. These results suggest that central NPY afferents to the NA-VL modulate the vagal preganglionic control of AV conduction and left ventricular contractility.

Synthesis of new benzoxazinone derivatives as neuropeptide Y5 antagonists for the treatment of obesity

Screening of our internal chemical collection against the neuropeptide Y5 (NPY Y5) receptor allowed the identification of a benzoxazine derivative 5f as a hit that showed moderate affinity (IC(50) = 300 nM). With the aim of improving the in vitro potency, a series of 2-benzoxazinone derivatives have been synthesized and tested for NPY Y5 activity. Most of the compounds were found to be potent and selective NPY Y5 antagonists having nanomolar binding affinities for the NPY Y5 receptor and showing functional antagonism in the forskolin-induced cyclic AMP test. Prelimminary studies in order to understand the structure-activity relationship were undertaken. Selected compounds were further evaluated for in vivo efficacy, affording the lead compound 2-[4-(8-methyl-2-oxo-4H-benzo[d][1,3]oxazin-1-yl)piperidin-1-yl]-N-(9-oxo-9H-fluoren-3-yl)acetamide 5p, which displayed in vivo activity reducing food intake in rodents.

Central NPY receptor-mediated alteration of heart rate dynamics in mice during expression of fear conditioned to an auditory cue

Neuropeptide Y (NPY) is involved in the regulation of emotionality including fear and anxiety, which modulate autonomic control of cardiovascular function. We therefore investigated the central effects of porcine NPY, selective Y1, Y2 and Y5 receptor agonists and a Y1 receptor antagonist on heart rate (HR) and HR variability in freely moving mice using auditory fear conditioning. Intracerebroventricular (i.c.v.) injections were applied 15 min before the tone-dependent memory test. NPY dose-dependently induced bradycardia associated with decreased HR variability, and blunted the stress-induced tachycardic response. The selective Y1 receptor antagonist BIBO 3304 blocked the NPY- and Y1-receptor agonist-induced suppression of conditioned tachycardia without affecting basal HR. The tachycardia elicited by both conditioned and unconditioned stressor was effectively attenuated by the Y1 receptor agonist. These results suggest a specific contribution of Y1, but not Y2 and Y5 receptors, to modulation of emotional responses most likely unrelated to impairment or modulation of memory. The NPY-induced bradycardia is attributed to not yet characterized NPY receptor subtypes other than Y1, Y2 and Y5, or a complex receptor interaction. In conclusion, NPY mediates central inhibition of sympathetic outflow, potentially coupled with attenuation of parasympathetic tone, i.e., mechanisms that may be associated with the reported anxiolytic action.

Selective activation of central NPY Y1 vs. Y5 receptor elicits hyperinsulinemia via distinct mechanisms

Central administration of neuropeptide Y (NPY) stimulates hyperphagia and hyperinsulinemia. Recent evidence has suggested that the Y1 and Y5 receptor subtypes may both mediate NPY-stimulated feeding. The present study attempts to further characterize the role of central NPY receptor subtypes involved in hyperinsulinemia. NPY and peptide analogs of NPY that selectively activated the NPY Y1 or Y5 receptor subtype induced feeding and hyperinsulinemia in satiated Long Evans rats, whereas NPY analogs that selectively activated the NPY Y2 or Y4 receptor subtype did not. To determine whether NPY-induced hyperinsulinemia is secondary to its hyperphagic effect, we compared the plasma insulin levels in the presence and absence of food after a 1-min central infusion of NPY and its analogs at 15, 60, and 120 min postinfusion. Our data suggest that selective activation of central NPY Y1 receptor subtype induced hyperinsulinemia independent of food ingestion, whereas the NPY Y5 receptor-induced hyperinsulinemia was dependent on food ingestion. Central administration of the selective Y1 receptor agonist D-Arg25 NPY eventually decreased plasma glucose levels 2 h postinfusion in Long Evans rats.

In vitro effects of mammalian leptin, neuropeptide-Y, β-endorphin and galanin on transcript levels of thyrotropin β and common α subunit mRNAs in the pituitary of bighead carp (aristichthys nobilis)

Thyrotropin (thyroid stimulating hormone, TSH) is a member of the pituitary glycoprotein hormones, consisting of two dissimilar subunits, alpha and beta. The two subunits are produced by different genes and are regulated independently. We have previously cloned a TSHbeta cDNA from bighead carp pituitary and investigated its gene regulation. We report here the direct effects of mammalian TSH-releasing hormone (TRH), leptin, neuropeptide-Y (NPY), beta-endorphin and galanin on mRNA levels of both TSHbeta and alpha-subunits in the pituitary of bighead carp in vitro. The dispersed pituitary cells of bighead carp were incubated at 25 degrees C for 6 h with different doses of these factors. The relative mRNA levels of TSHbeta and alpha-subunits were estimated by traditional polymerase chain reaction (PCR) analysis and fluorescence real-time PCR analysis. The results revealed that mammalian TRH, leptin and beta-endorphin produced dose-dependent stimulatory effects on mRNA levels of both TSHbeta and alpha-subunits while thyroxine (T4) and mammalian galanin suppressed mRNA levels of both TSHbeta and alpha-subunits. NPY suppressed TSHbeta mRNA level, but stimulated alpha-subunit mRNA level. This study has demonstrated that mammalian TRH, leptin, NPY, beta-endorphin and galanin were active in modulating the steady-state mRNA levels of TSHbeta and alpha-subunits of bighead carp pituitary in vitro. The results suggest that endogenous TRH, leptin, NPY, beta-endorphin and galanin may modulate transcript levels of TSHbeta and alpha-subunits in pituitary of bighead carp.

Functional autoradiography of neuropeptide Y Y1 and Y2 receptor subtypes in rat brain using agonist stimulated [35S]GTPgammaS binding

Neuropeptide Y, one of the most abundant brain peptides, has been found to modulate several important biological functions via a family of G-protein coupled receptors. To investigate the localization of functional NPY receptor subtypes in the rat brain, we performed agonist-induced [35S]GTPgammaS autoradiography. The Y1/Y4/Y5 agonist Leu(31), Pro(34)-NPY increased [35S]GTPgammaS binding in several brain areas with a regional distribution consistent with that produced when labeling adjacent sections with [125I]-Leu(31), Pro(34)-PYY. The Y1 selective antagonist BIBP3226 antagonized the Leu(31), Pro(34)-NPY stimulated increase in [35S]GTPgammaS binding in all areas examined. The Y2 agonist C2-NPY stimulated [35S]GTPgamma binding in numerous brain areas with a regional distribution similar to the binding observed with [125I]-PYY 3-36. No increase in [35S]GTPgammaS binding above basal was observed in any brain area evaluated using Y4 and Y5 selective agonists. This study demonstrates abundant Y1 and Y2 receptor activation in the rat brain, while evidence for functional Y4 and Y5 receptors was not observed.

Neuroendocrine pharmacology of stress

Exposure to hostile conditions initiates responses organized to enhance the probability of survival. These coordinated responses, known as stress responses, are composed of alterations in behavior, autonomic function and the secretion of multiple hormones. The activation of the renin-angiotensin system and the hypothalamic-pituitary-adrenocortical axis plays a pivotal role in the stress response. Neuroendocrine components activated by stressors include the increased secretion of epinephrine and norepinephrine from the sympathetic nervous system and adrenal medulla, the release of corticotropin-releasing factor (CRF) and vasopressin from parvicellular neurons into the portal circulation, and seconds later, the secretion of pituitary adrenocorticotropin (ACTH), leading to secretion of glucocorticoids by the adrenal gland. Corticotropin-releasing factor coordinates the endocrine, autonomic, behavioral and immune responses to stress and also acts as a neurotransmitter or neuromodulator in the amygdala, dorsal raphe nucleus, hippocampus and locus coeruleus, to integrate brain multi-system responses to stress. This review discussed the role of classical mediators of the stress response, such as corticotropin-releasing factor, vasopressin, serotonin (5-hydroxytryptamine or 5-HT) and catecholamines. Also discussed are the roles of other neuropeptides/neuromodulators involved in the stress response that have previously received little attention, such as substance P, vasoactive intestinal polypeptide, neuropeptide Y and cholecystokinin. Anxiolytic drugs of the benzodiazepine class and other drugs that affect catecholamine, GABA(A), histamine and serotonin receptors have been used to attenuate the neuroendocrine response to stressors. The neuroendocrine information for these drugs is still incomplete; however, they are a new class of potential antidepressant and anxiolytic drugs that offer new therapeutic approaches to treating anxiety disorders. The studies described in this review suggest that multiple brain mechanisms are responsible for the regulation of each hormone and that not all hormones are regulated by the same neural circuits. In particular, the renin-angiotensin system seems to be regulated by different brain mechanisms than the hypothalamic-pituitary-adrenal system. This could be an important survival mechanism to ensure that dysfunction of one neurotransmitter system will not endanger the appropriate secretion of hormones during exposure to adverse conditions. The measurement of several hormones to examine the mechanisms underlying the stress response and the effects of drugs and lesions on these responses can provide insight into the nature and location of brain circuits and neurotransmitter receptors involved in anxiety and stress.

Differential effects of carvedilol and atenolol on plasma noradrenaline during exercise in humans

AIMS

Evidence of long-term beneficial effects of beta-blockers on mortality and morbidity in patients with heart failure has been demonstrated in recent randomized trials. However, not all beta-blockers are identical. Carvedilol, a nonselective beta- and alpha-adrenergic blocker, can potentially blunt the release of noradrenaline by blocking presynaptic beta2-adrenergic receptors. To test this hypothesis, we have compared the effects of carvedilol and atenolol on plasma noradrenaline during exercise in healthy young volunteers.

METHODS

This study investigated the differential effects of 2 weeks pretreatment with carvedilol 25 mg day(-1) and atenolol 50 mg day(-1) on plasma noradrenaline at rest and during exercise on a treadmill in a double-blind randomized crossover study, involving 12 healthy male volunteers (mean age 21.6 +/- 0.3 years).

RESULTS

Haemodynamic parameters at rest and during exercise were not significantly different in either carvedilol or atenolol pretreatment groups. However, carvedilol pretreatment significantly blunted the increase in plasma noradrenaline during exercise [393.8 +/- 51.7 pg ml(-1) (pretreatment) to 259.7 +/- 21.2 pg ml(-1) (post-treatment)], when compared with atenolol [340.4 +/- 54.6 pg ml(-1) (pretreatment) to 396.2 +/- 32.0 pg ml(-1) (post-treatment)]. The difference between carvedilol and atenolol (95% confidence interval) was -145.2, -351.0, P < 0.05.

CONCLUSIONS

We have demonstrated that carvedilol but not atenolol significantly blunted the increase in plasma noradrenaline during exercise. These findings may suggest a sympathoinhibitory effect of carvedilol that may enhance its ability to attenuate the cardiotoxicity associated with adrenergic stimulation in patients with heart failure.

Distribution of neuropeptide Y Y1 receptors in rodent peripheral tissues

Using a sensitive immunohistochemical technique, the localization of neuropeptide Y (NPY) Y1-receptor (Y1R)-like immunoreactivity (LI) was studied in various peripheral tissues of rat. Wild-type (WT) and Y1R-knockout (KO) mice were also analyzed. Y1R-LI was found in small arteries and arterioles in many tissues, with particularly high levels in the thyroid and parathyroid glands. In the thyroid gland, Y1R-LI was seen in blood vessel walls lacking alpha-smooth muscle actin, i.e., perhaps in endothelial cells of capillaries. Larger arteries lacked detectable Y1R-LI. A distinct Y1R-immunoreactive (IR) reticulum was seen in the WT mouse spleen, but not in Y1R-KO mouse or rat. In the gastrointestinal tract, Y1R-positive neurons were observed in the myenteric plexus, and a few enteroendocrine cells were Y1R-IR. Some cells in islets of Langerhans in the pancreas were Y1R-positive, and double immunostaining showed coexistence with somatostatin in D-cells. In the urogenital tract, Y1R-LI was observed in the collecting tubule cells of the renal papillae and in some epithelial cells of the seminal vesicle. Some chromaffin cells of adrenal medulla were positive for Y1R. The problem of the specificity of the Y1R-LI is evaluated using adsorption tests as well as comparisons among rat, WT mouse, and mouse with deleted Y1R. Our findings support many earlier studies based on other methodologies, showing that Y1Rs on smooth muscle cells of blood vessels mediate NPY-induced vasoconstriction in various organs. In addition, Y1Rs in other cells in parenchymal tissues of several organs suggest nonvascular effects of NPY via the Y1R.

The neuropeptide Y monomer in solution is not folded in the pancreatic-polypeptide fold

Fluorescence-labelled analogs of NPY, a 36-amino acid peptide amide, were synthesized by solid-phase peptide synthesis and used for fluorescence-resonance energy transfer studies to investigate the conformation. Energy-transfer efficiency measurements in different media at the concentration of 10 microM are in agreement with a model of the NPY structure proposed by NMR studies (performed at millimolar concentration) in which the C-terminal part of the molecule adopts an alpha-helical conformation while the N-terminal part is flexible. According to this model, the alpha-helix is stabilized by intermolecular hydrophobic interactions because of the formation of dimers. The decrease of the peptide concentration causes a shift of the dimerization equilibrium toward the monomeric form. Energy-transfer efficiency measurements performed at lower concentrations do not support the hypothesis of the folding back of the N-terminal tail onto the C-terminal alpha-helix to yield the so-called "PP-fold" conformation. This structure is observed in the crystal structure of avian pancreatic polypeptide, a member of the NPY peptide hormone family, and it has been considered to be the bioactive one. Our results complete the structural characterization of NPY in solution at concentration ranges in which NMR experiments are not feasible. Furthermore, these results open the way to study the conformation of the receptor-bound ligand.

Neuropeptide Y receptors as targets for anti-obesity drug development: perspective and current status

Neuropeptide Y is a widely distributed neuropeptide that elicits a plethora of physiological effects via interaction with six different receptors (Y(1)-y(6)). Recent attention has focused on the role of neuropeptide Y in the regulation of energy homeostasis. Neuropeptide Y stimulates food intake, inhibits energy expenditure, increases body weight and increases anabolic hormone levels by activating the neuropeptide Y Y(1) and Y(5) receptors in the hypothalamus. Based on these findings, several neuropeptide Y Y(1) and Y(5) receptor antagonists have been developed recently as potential anti-obesity agents. In addition, mice lacking neuropeptide Y, the neuropeptide Y Y(1) receptor or the neuropeptide Y Y(5) receptor have been generated. The data obtained to date with these newly developed tools suggests that neuropeptide Y receptor antagonists, particularly neuropeptide Y Y(1) receptor antagonists, may be useful anti-obesity agents. However, the redundancy of the neurochemical systems regulating energy homeostasis may limit the effect of ablating a single pathway. In addition, patients in whom the starvation response is activated, such as formerly obese patients who have lost weight or patients with complete or partial leptin deficiency, may be the best candidates for treatment with a neuropeptide Y receptor antagonist.

Diverse functions of neuropeptide Y revealed using genetically modified animals

Neuropeptide Y (NPY), a peptide abundantly expressed in the mammalian nervous system, has been extensively studied using traditional pharmacological and behavioral models. Central administration of NPY or synthetic ligands for its receptors has indicated a role of NPY in anxiety-related behaviors, feeding, regulation of blood pressure, circadian rhythm and other functions. Some limitations inherent in pharmacological approaches, such as lack of selectivity of receptor antagonists, can be elegantly circumvented using genetically modified animals. For NPY, mice lacking NPY, the Y1, the Y2 or the Y5 receptors have been generated. In addition, both mice and rats overexpressing NPY in the central nervous system are available. Here, we review the research carried out so far in the NPY-field using genetically modified animals. Together, these models indicate that stress-related behaviors and regulation of voluntary alcohol intake perhaps are among the most important functions of central NPY, and may provide attractive targets for developing novel therapies in depression, anxiety disorders and alcohol dependence.

Increased insulin concentrations and glucose storage in neuropeptide Y Y1 receptor-deficient mice

Mice lacking NPY Y1 receptors develop obesity without hyperphagia indicating increased energy storage and/or decreased energy expenditure. Then, we investigated glucose utilization in these animals at the onset of obesity. Fasted NPY Y1 knockouts showed hyperinsulinemia associated with increased whole body and adipose tissue glucose utilization and glycogen synthesis but normal glycolysis. Since leptin modulates NPY actions, we studied whether the lack of NPY Y1 receptor affected leptin-mediated regulation of glucose metabolism. Leptin infusion normalized hyperinsulinemia and glucose turnover. These results suggest a possible mechanism for the development of obesity without hyperphagia via dysfunction in regulatory loops involving NPY, leptin and insulin.

Effects of BIBP3226 and BIBP3435 on cytosolic calcium in neuropeptide Y Y1 receptor-transfected Chinese hamster ovary cells and wild type CHO-K1 cells

The NPY Y1-receptor selective antagonist BIBP3226 exerts a dual control on the cytosolic free calcium concentration ([Ca2+]i) in NPY Y1 receptor-transfected Chinese Hamster Ovary Cells (CHO-Y1 cells). It is a potent inhibitor of the NPY-evoked increase in [Ca2+]i. This can be ascribed to its antagonistic properties for the NPY Y, receptor since its less active stereoisomer, BIBP3435, is much less potent. However, when its concentration exceeds 1 microM, BIBP3226 produces a large increase in [Ca2+]i on its own. This effect is mimicked by BIBP3435 and it also occurs in wild type CHO-K1 cells. These latter cells do not contain high affinity binding sites for [3H]NPY and [3H]BIBP3226 and, hence, no endogenous NPY Y1 receptors. It is concluded that, at moderately high concentrations, the NPY Y1 receptor antagonist BIBP3226 and its entantiomer BIBP3435 are able to increase the [Ca2+ ]i in CHO cells either by stimulating another receptor or by directly affecting cellular mechanisms that are involved in calcium homeostasis.

Structure and dynamics of micelle-bound neuropeptide Y: comparison with unligated NPY and implications for receptor selection

The biological importance of the neuropeptide Y (NPY) has steered a number of investigations about its solution structure over the last 20 years. Here, we focus on the comparison of the structure and dynamics of NPY free in solution to when bound to a membrane mimetic, dodecylphosphocholine (DPC) micelles, as studied by 2D (1)H NMR spectroscopy. Both, free in solution and in the micelle-bound form, the N-terminal segment (Tyr1-Glu15) is shown to extend like a flexible tail in solution. This is not compatible with the PP-fold model for NPY that postulates backfolding of the flexible N terminus onto the C-terminal helix. The correlation time (tau(c)) of NPY in aqueous solution, 5.5 (+/-1.0) ns at 32 degrees C, is only consistent with its existence in a dimeric form. Exchange contributions especially enhancing transverse relaxation rates (R(2)) of residues located on one side of the C-terminal helix of the molecule are supposed to originate from dimerization of the NPY molecule. The dimerization interface was directly probed by looking at (15)N-labeled NPY/spin-labeled [TOAC34]-[(14)N]-NPY heterodimers and revealed both parallel and anti-parallel alignment of the helices. The NMR-derived three-dimensional structure of micelle-bound NPY at 37 degrees C and pH 6.0 is similar but not identical to that free in solution. The final set of 17 lowest-energy DYANA structures is particularly well defined in the region of residues 21-31, with a mean pairwise RMSD of 0.23 A for the backbone heavy atoms and 0.85 A for all heavy atoms. The combination of NMR relaxation data and CD measurements clearly demonstrates that the alpha-helical region Ala18-Thr32 is more stable, and the C-terminal tetrapeptide becomes structured only in the presence of the phosphocholine micelles. The position of NPY relative to the DPC micelle surface was probed by adding micelle integrating spin labels. Together with information from (1)H,(2)H exchange rates, we conclude that the interaction of NPY with the micelle is promoted by the amphiphilic alpha-helical segment of residues Tyr21-Thr32. NPY is located at the lipid-water interface with its C-terminal helix parallel to the membrane surface and penetrates the hydrophobic interior only via insertions of a few long aliphatic or aromatic side-chains. From these data we can demonstrate that the dimer interface of neuropeptide Y is similar to the interface of the monomer binding to DPC-micelles. We speculate that binding of the NPY monomer to the membrane is an essential key step preceeding receptor binding, thereby pre-orientating the C-terminal tetrapeptide and possibly inducing the bio-active conformation.

Dissociation of potentiation of Leu31 Pro34 neuropeptide Y on adrenergic and purinergic transmission in isolated canine splenic artery

The present study observed the effects of an activation of neuropeptide Y (NPY) Y1 receptors on adrenergic and purinergic components of double-peaked vasoconstrictor responses to periarterial nerve stimulation in the isolated, perfused canine splenic arteries. The results showed that 3-30 nM Leu31 Pro34 neuropeptide Y (LP-NPY) produced a dose-dependent potentiation of double-peaked vasoconstrictor responses to trains of 30-s pulses at 1, 4 or 10 Hz of stimulation. The potentiation of LP-NPY of the nerve-stimulated vasoconstrictions were completely inhibited by subsequent blockade of alpha1-adrenoceptors or Y1 receptors with 0.1 microM prazosin or with 1 microM BIBP 3226 ((R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-argininami de), respectively. The remaining responses in the presence of LP-NPY and prazosin were abolished by P2X receptor desensitization with 1 microM alpha,beta-methylene ATP. Moreover, 30 nM LP-NPY failed to modify the vasoconstrictor responses to nerve stimulation after treatment with prazosin. A subsequent administration of alpha,beta-methylene ATP completely suppressed the remaining responses after prazosin and LP-NPY. The vasoconstrictions induced by 0.003-1 nmol noradrenaline and 0.003-1 micromol ATP were slightly, but not significantly enhanced by 30 nM LP-NPY. The observations indicated that activation of postjunctional NPY Y1 receptors may have an important role in the modulation of adrenergic rather than purinergic transmission of the sympathetic co-transmission.

Neuropeptide Y (NPY) potentiates phenylephrine-induced mitogen-activated protein kinase activation in primary cardiomyocytes via NPY Y5 receptors

Neuropeptide Y (NPY) has been shown to participate in the cardiovascular response mediated by the sympathetic system. In this report, we investigate the growth factor properties of NPY on cardiac myocytes. Mitogen-activated protein kinases (MAPK) are key signaling molecules in the transduction of trophic signals. Therefore, the role of NPY in inducing MAPK activation was studied in mouse neonatal cardiomyocytes. Exposure of neonatal cardiomyocytes to either NPY, phenylephrine, or angiotensin II induces a rapid phosphorylation of the extracellular responsive kinase, the c-jun N-terminal kinase, and the p38 kinase as well as an activation of protein kinase C (PKC). Moreover, NPY potentiates phenylephrine-induced MAPK and PKC stimulation. In contrast, NPY has no synergistic effect on angiotensin II-stimulated MAPK phosphorylation or PKC activity. NPY effects are pertussis toxin-sensitive and calcium-independent and are mediated by NPY Y5 receptors. Taken together, these results suggest that NPY, via G(i) protein-coupled NPY Y5 receptors, could participate in the development of cardiac hypertrophy during chronic sympathetic stimulation by potentiating alpha-adrenergic signals.

Neuropeptide Y induced increase of cytosolic and nuclear Ca2+ in heart and vascular smooth muscle cells

It was reported that neuropeptide Y (NPY) affects cardiac and vascular smooth muscle (VSM) function probably by increasing intracellular Ca2+. In this study, using fura-2 microfluorometry and fluo-3 confocal microscopy techniques for intracellular Ca2+ measurement, we attempted to verify whether the action of NPY receptor's stimulation in heart and VSM cells modulates intracellular Ca2+ and whether this effect is mediated via the Y1 receptor type. Using spontaneously contracting single ventricular heart cells of 10-day-old embryonic chicks and the fluo-3 confocal microscopy Ca2+ measurement technique to localize cytosolic ([Ca]c) and nuclear ([Ca]n) free Ca2+ level and distribution, 10-10 M of human (h) NPY significantly (P < 0.05) increased the frequency of cytosolic and nuclear Ca2+ transients during spontaneous contraction. Increasing the concentration of hNPY (10-9 M) did not further increase the frequency of Ca2+ transients. The L-type Ca2+ channel blocker, nifedipine (10-5 M), significantly (P < 0.001) blocked the spontaneous rise of intracellular Ca2+ in the absence and presence of hNPY (10-10 and 10-9 M). However, the selective Y1 receptor antagonist, BIBP3226 (10-6 M), significantly decreased the hNPY-induced (10-10 and 10-9 M) increase in the frequency of Ca2+ transients back to near the control level (P < 0.05). In resting nonworking heart and human aortic VSM cells, hNPY induced a dose-dependent sustained increase of basal resting intracellular Ca2+ with an EC50 near 10-9 M. This sustained increase was cytosolic and nuclear and was completely blocked by the Ca2+ chelator EGTA, and was significantly decreased by the Y1 receptor antagonist BIBP3226 in both heart (P < 0.05) and VSM (P < 0.01) cells. These results strongly suggest that NPY stimulates the resting basal steady-state Ca2+ influx through the sarcolemma and induces sustained increases of cytosolic and nuclear calcium, in good part, via the activation of the sarcolemma membrane Y1 receptor type in both resting heart and VSM cells. In addition, NPY also increased the frequency of Ca2+ transients during spontaneous contraction of heart cells mainly via the activation of the Y1 receptor type, which may explain in part the active cardiovascular action of this peptide.Key words: heart, vascular smooth muscle, neuropeptide Y, BIBP3226, calcium, nucleus.

The molecular basis of penile erection

Over the past two decades our understanding of the physiology and the various mediators involved in the pathway of penile erection has greatly increased. This has enabled us to develop effective pharmacological treatments for ED.

Molecular dynamics of NPY Y1 receptor activation

A three-dimensional model of the human neuropeptide Y(NPY)Y1 receptor (hY1) was constructed, energy refined and used to simulate molecular receptor interactions of the peptide ligands NPY, [L31, P34]NPY, peptide YY (PYY) and pancreatic polypeptide (PP), and of the nonpeptide antagonist R-N2-(diphenylacetyl)-N-(4-hydroxyphenyl)methyl-argininamide (BIBP3226) and its S-enantiomer BIBP3435. The best complementarity in charges between the receptor and the peptides, and the best structural accordance with experimental studies, was obtained with amino acid 1-4 of the peptides interacting with Asp194, Asp200, Gln201, Phe202 and Trp288 in the receptor. Arg33 and Arg35 of the peptides formed salt bridges with Asp104 and Asp287, respectively, while Tyr36 interacted in a binding pocket formed by Phe41, Thr42, Tyr100, Asn297, His298 and Phe302. Calculated electrostatic potentials around NPY and hY1 molecules indicated that ligand binding is initiated by electrostatic interactions between a highly positive region in the N- and C-terminal parts of the peptides, and a negative region in the extracellular receptor domains. Molecular dynamics simulations of NPY and BIBP3226 interactions with the receptor indicated rigid body motions of TMH5 and TMH6 upon NPY binding as mechanisms of receptor activation, and that BIBP3226 may act as an antagonist by constraining these motions.

Role of hypothalamic neuropeptide Y in feeding and obesity

The 36-amino-acid peptide, neuropeptide Y (NPY), is the most abundant peptide in the rat brain. When administered into the brain, NPY produces a variety of physiological actions including a pronounced stimulation of feeding in satiated rats. Elevations in hypothalamic NPY have been reported after food deprivation and in genetically obese rodents. NPY is believed to produce its actions through a portfolio of G-protein coupled receptors, Y1, Y2, Y4 and Y5. Studies using peptide analogs, receptor knockout animals and specific receptor antagonists suggest the Y1 and Y5 receptors are important in mediating the effects of NPY on food intake in rats. Development of specific receptor antagonists with improved pharmacokinetic properties will be required to determine the importance of NPY in human obesity and appetite disorders.

Labelling of peptides with 1.4-nm gold particles to demonstrate their binding sites in the rat spinal cord

Recently we presented a method to label the neuropeptide substance P with a 1.4-nm gold particle covalently bound at the N-terminus that can be used for demonstrating its binding sites in histological sections. In this study we examined whether the peptides neuropeptide Y, somatostatin, calcitonin gene-related peptide and bradykinin can be labelled in the same way. Polyacrylamide gel electrophoresis revealed a reduction in mobility for peptide-gold conjugates over gold particles alone consistent with peptide binding. In cryostat sections of the rat lumbar spinal cord, the peptides showed a distinct binding pattern in the grey matter corresponding to data of studies using autoradiographic methods. Therefore, we conclude that this simple and fast method can be used for labelling peptides in general to demonstrate their binding sites in histological sections, provided the peptide binds by its C-terminus.

Comparative vascular responses in elasmobranchs to different structures of neuropeptide Y and peptide YY

The vascular responses to neuropeptide Y (NPY) and peptide YY (PYY) were tested in several species of elasmobranchs to assess whether changes in sequence in these neuropeptides from elasmobranchs to mammals are associated with different physiological responses. NPY-like immunoreactivity was detected in the gut and in nerve fibres surrounding some, but not all, blood vessels of six species. Intravenous injection of dogfish, frog and human NPY in anaesthetised fish caused similar vasopressor effects in the three species tested, except human NPY which lowered blood pressure in one of the three. Dogfish NPY and PYY were equipotent pressor agents in two species, but PYY was significantly more potent than NPY in one species. NPY and PYY both contracted isolated gut arteries from three species, but had no effect on isolated efferent arteries tested. In conclusion, differential vascular responses in elasmobranchs are not associated with changes in NPY sequence across vertebrates, but may be with changes in PYY in some species.

Altered neuropeptide Y Y1 responses in mesenteric arteries in rats with congestive heart failure

The aim of the present study was to elucidate if the potentiating effect of neuropeptide Y on various vasoactive agents in vitro is (1) altered in mesenteric arteries from rats with congestive heart failure and (2) mediated by the neuropeptide Y Y1 receptor. The direct vascular effects of neuropeptide Y and its modulating effects on the contractions induced by endothelin-1-, noradrenaline-, 5-hydroxytryptamine (5-HT)-, U46619-(9,11-dideoxy-11alpha, 9alpha-epoxymethano-prostaglandin F2alpha) and ATP, and acetylcholine-induced dilatations were studied in the presence and absence of the neuropeptide Y Y1 antagonist, BIBP3226 (BIBP3226¿(R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl ]-D-arginine-amide¿). Neuropeptide Y, per se, had no vasoactive effect in the arteries. The potency of endothelin-1 was significantly decreased in congestive heart failure rats. Neuropeptide Y and neuropeptide Y-(13-36) potentiated the endothelin-1-induced contraction in congestive heart failure mesenteric arteries. In 20% of the congestive heart failure rats, sarafotoxin 6c induced a contraction of 31+/-4%. Neuropeptide Y also potentiated U46619- and noradrenaline-induced contractions but not 5-HT-induced contractions in congestive heart failure arteries. In sham-operated animals neuropeptide Y potentiated noradrenaline- and 5-HT-induced contractions. These potentiations were inhibited by BIBP3226. Acetylcholine induced an equipotent relaxation in both groups which was unaffected by neuropeptide Y. In conclusion, neuropeptide Y responses are altered in congestive heart failure rats. The potentiating effect differs between vasoactive substances. Neuropeptide Y Y1 and non-neuropeptide Y1 receptors are involved.

Endogenous neuropeptide Y mediates vasoconstriction during endotoxic and hemorrhagic shock

Neuropeptide Y (1-36), NPY, is a sympathetic vasoconstrictor whose activities in blood vessels is determined by the presence of vasoconstrictive Y1 receptors and the enzyme dipeptidyl peptidase IV (DPPIV), which converts NPY to non-vasoconstrictive peptides. While the role of the NPY system has been established during cold water stress, its role in hypotensive conditions has not; yet, exogenous NPY improves hemodynamics and survival in rats with endotoxic shock. We used a new selective non-peptidergic Y1 receptor antagonist, BIBP-3226, to determine the role of the endogenous NPY/Y1 system in endotoxic shock (induced by i.v. injection of 10 mg/kg of Escherichia coli lipopolysaccharide 0127:B8, LPS) and hemorrhagic shock (bleeding of 15 ml/kg over 1.5 min). Conscious rats received a bolus of BIBP-3226 or the vehicle 5 min before endotoxin challenge or induction of hemorrhage, followed by continuous infusion. Mean arterial pressure (MAP) at 5 min after LPS administration dropped in the control group by 15%, compared to 36% in the BIBP-3226-treated group (p < 0.01). Similarly, the hemorrhage-induced drop in MAP in the control group was 32% at 5 min, compared to 53% in the BIBP-treated rats (p < 0.01). Plasma NPY levels were unchanged in the endotoxic shock group, but were significantly elevated in the hemorrhagic shock group. BIBP-3226 pretreatment abrogated the increased plasma NPY levels after hemorrhagic shock. Endogenous NPY contributes to blood pressure recovery during endotoxic and hemorrhagic shock.

Mechanisms of vascular growth-promoting effects of neuropeptide Y: role of its inducible receptors

We have previously reported that neuropeptide Y (NPY), a sympathetic cotransmitter and vasoconstrictor, is mitogenic for vascular smooth muscle cells (VSMCs), and now report on the mechanisms mediating these effects. In rat aortic A10 cell line, NPY's potency was greater than that of norepinephrine, and efficacy similar to that of platelet-derived growth factor, but less than that of the full serum, in stimulating cell proliferation; this effect was optimal in cell 60-80% cell density. At lower cell density and serum content, NPY stimulated DNA fragmentation/apoptosis. In rat aortic primary VSMCs (RASMCs), mitogenic effect of NPY was bimodal with the first peak at 1 pM, a decline at 1 nM, and a second peak at 10-100 nM; peptide YY had similar but less efficacious effects. The first NPY's peak was mimicked by Y2 agonists, and blocked by Y2 antagonist (T4-[NPY(33-36]4), and the second mimicked by Y1 agonist and partially blocked by Y1 antagonist, BIBP3226, suggesting a multireceptor mode of action. In A10 and in RASMCs, the expression of NPY receptors, Y1, Y2 and Y5, using RT-PCR was undetectable in quiescent cells but detected after pre-treatment with NPY. The receptor induction was NPY dose-dependent and also affected by incubation time and presence of serum. The NPY mitogenic effects were attenuated by calcium channel blockers, particularly verapamil. In primary cultures of rat coronary endothelial cells (where NPY is also mitogenic), NPY stimulated mitogen-activated protein kinase (MAPK) activity. Thus, the growth-promoting effects of NPY in vascular cells occur at concentrations lower than vasoconstrictive, and appear to be mediated by inducible Y1, Y2, and Y5 receptors, calcium entry and possibly MAPK activation.

Is there really an NPY Y3 receptor?

NPY is an abundant neuropeptide that is widely distributed throughout the central and peripheral nervous systems. Based on pharmacological and cloning data, there are believed to be six different types of NPY receptors. The Y3 receptor is the only one of the six that has not been cloned or well characterized. Y3 receptors have been shown to be important in the regulation of visceral afferents within the nucleus tractus solitarius (NTS). In the present experiments, we have compared the effects of NPY and various analogs on Ba2+ currents in acutely dissociated neurons from the NTS and the neighboring area postrema (AP). No neurons from either NTS or AP responded to [D-Trp32]NPY suggesting that these areas lack Y5 receptors. However, we found a group of NTS neurons that only responded to NPY and not PYY or any other analogs. This agonist profile corresponds to that described for NPY Y3 receptors. No AP neurons showed this type of agonist profile. Other neurons responded to a variety of NPY analogs indicating the presence of Y1, Y2, and Y4 receptors in both nuclei.

Regional distribution of neuropeptide Y Y2 receptor messenger RNA in the human post mortem brain

The neuropeptide Y Y2 receptor is one of six receptor subtypes mediating the multiform physiological actions of neuropeptide Y. The Y2 receptor has been demonstrated to be the most predominant receptor subtype in the human brain and appears to be involved in many neuropeptide Y actions, such as the regulation of locomotor activity, cardiovascular functions, memory processing, circadian rhythms and release of other neurotransmitters. We have recently demonstrated the widespread and abundant distribution of neuropeptide Y Y1 receptor messenger RNA in the human cerebral cortex (different laminar patterns within distinct cortical regions), hippocampal dentate gyrus and striatum. To assess a possible differential distribution of Y1 and Y2 receptor messenger RNAs, the regional expression of neuropeptide Y Y2 messenger RNA-containing cells in the human brain was analysed, in particular within the cerebral cortex and striatum. In situ hybridization experiments revealed the localization of the Y2 messenger RNA signal throughout all cortical regions, with the highest intensity per cell apparent in lamina IV, with the exception of the striate cortex, which showed an intense labelling primarily in layer VI. The striatum expressed low to undetectable levels of the Y2 receptor messenger RNA. The dentate gyrus and the CA2 region presented the highest hybridization signals, while a very weak Y2 messenger RNA expression was found in the CA1 region and subiculum. Positive Y2 messenger RNA hybridization signals were also detected in the lateral geniculate nucleus, amygdala, substantia nigra, hypothalamus, cerebellum and choroid plexus. These results demonstrate the widespread distribution of neuropeptide Y Y2 receptor messenger RNA in the human brain, with a pattern of expression distinct from the Y1 subtype, suggesting that these two receptor subtypes may mediate different neuropeptide Y functions in the human brain, mainly through actions on different neuronal systems.

The distribution of nitric oxide synthase-, adenosine deaminase- and neuropeptide Y-immunoreactivity through the entire rat nucleus tractus solitarius: Effect of unilateral nodose ganglionectomy

The present study has employed immunocytochemistry on free-floating sections of adult rat medulla oblongata to characterise the distribution of nitric oxide synthase- (NOS), adenosine deaminase- (ADA) and neuropeptide Y- (NPY) immunoreactivity (IR) throughout the entire rostro-caudal axis of the nucleus tractus solitarius (NTS). In addition, unilateral nodose ganglionectomy was performed in a group of rats to determine whether any observed immunoreactivity was associated with central vagal afferent terminals. NOS-IR was found throughout the entire NTS, in cells, and both varicose and non-varicose fibres. Furthermore, unilateral nodose ganglionectomy resulted in a clear reduction in NOS-IR (visualised with diaminobenzidine) in a highly restricted portion of the ipsilateral medial NTS. Similarly, ADA- and NPY-containing cells, fibres and terminals were also found throughout the adult rat NTS. However, following unilateral nodose ganglionectomy, there was no apparent reduction in either ADA-IR or NPY-IR on the denervated side of the NTS. These data indicate a role for nitric oxide, purines and neuropeptide Y as neuromodulators within the rat NTS, although only nitric oxide appears to be primarily associated with vagal afferent input. Adenosine deaminase and neuropeptide Y-containing neurons appear to be predominantly postsynaptic to vagal input, although their possible association with vagal afferents cannot be completely excluded.

Cardiovascular response, feeding behavior and locomotor activity in mice lacking the NPY Y1 receptor

Neuropeptide Y (NPY) is a 36-amino-acid neurotransmitter which is widely distributed throughout the central and peripheral nervous system. NPY involvement has been suggested in various physiological responses including cardiovascular homeostasis and the hypothalamic control of food intake. At least six subtypes of NPY receptors have been described. Because of the lack of selective antagonists, the specific role of each receptor subtype has been difficult to establish. Here we describe mice deficient for the expression of the Y1 receptor subtype. Homozygous mutant mice demonstrate a complete absence of blood pressure response to NPY, whereas they retain normal response to other vasoconstrictors. Daily food intake, as well as NPY-stimulated feeding, are only slightly diminished, whereas fast-induced refeeding is markedly reduced. Adult mice lacking the NPY Y1 receptor are characterized by increased body fat with no change in protein content. The higher energetic efficiency of mutant mice might result, in part, from the lower metabolic rate measured during the active period, associated with reduced locomotor activity. These results demonstrate the importance of NPY Y1 receptors in NPY-mediated cardiovascular response and in the regulation of body weight through central control of energy expenditure. In addition, these data are also indicative of a role for the Y1 receptor in the control of food intake.

Neuropeptide Y: some viewpoints on a multifaceted peptide in the normal and diseased nervous system

Using immunohistochemical and in situ hybridization methodologies the localization of neuropeptide tyrosine (NPY) and two of its receptors, the Y1- and the Y2-receptor (R), has been analysed in various tissues in normal animals and animals subjected to different experimental procedures as well as animals with a genetic and an acquired disease. (1) Dorsal root ganglion (DRG) neurons are discussed with special focus on the effect of peripheral nerve injury. In normal DRG neurons NPY cannot be detected, whereas Y1-R mRNA and Y1-R-like immunoreactivity (LI) are strongly expressed. The Y1-Rs decorate the membrane of the cell soma and are not transported peripherally into the axonal branches. Y2-R mRNA levels are low. After axotomy there is a marked increase in NPY, a decrease in Y1-Rs and an increase in Y2-Rs. The Y2-R is transported centrifugally. These findings suggest that NPY-ergic mechanisms participate in the adaptive changes of sensory neurons in response to injury. (2) Using specific antibodies the cellular and subcellular localization of the Y1-R protein have been analysed in cerebral blood vessels. The results demonstrate high concentrations of receptors in smooth muscle cells around pial arterioles with lower numbers in large vessels on the basal surface of the brain. In many regions the receptors 'disappear' after the arterioles have entered the brain tissue. At the ultrastructural level the receptors are found both on the endothelial and peripheral side of the muscle cells as well as laterally, where muscle cells oppose each other. The receptor protein is often associated with small vesicles. No NPY-positive nerve fibers were found around the Y1-R-rich arterioles, but they were only seen around the arteries with low Y1-R levels. The Y1-R-rich arterioles were, however, seen close to numerous NPY-positive fibers originating from central interneurons. These findings raise the possibility that centrally originating NPY can influence cerebral blood flow, possibly by stimulating NPY-Rs on the peripheral side of the muscle cells. However, also blood borne NPY, released under special conditions, such as stress from sympathetic nerves and the adrenal medulla and transported with blood, may stimulate receptors on the endothelial side of the smooth muscle cells. (3) In the arcuate nucleus Y1- and Y2-Rs are found, whereby the Y1-Rs are located in its ventro-medial portion and co-localized with POMC peptides, and the Y2-R in its ventromedial part, partly co-localized with NPY. NPY nerve endings makes synaptic contact with the POMC/Y1-R-positive neurons. In a mouse model for genetic anorexia very high levels of NPY were observed in arcuate neurons as compared to control mice. However, NPY mRNA levels were not different between the two groups. Taken together these findings are in good agreement with the view that NPY in the arcuate nucleus plays an important role in regulating feeding behaviour. (4) After intracerebral prion inoculation in mice an upregulation of NPY mRNA levels was observed in CA3 pyramidal neurons, and this effect was seen at a time point just before the first behavioural symptoms were manifested. At approximately the same time there was a dramatic decrease in Y2-R binding in strata oriens and radiatum of the CA1 region of the hippocampus, whereas in other regions no changes or much smaller changes were observed. Also, there was only a very slight decrease in Y2-R mRNA levels in CA3 neurons. It thus appears as if the prion disease prevents ligand binding to the Y2-R, perhaps by influencing traffic of receptor proteins, possibly at the level of cell membrane-associated caveolae, which have been implicated in the conversion of normal protein to scrapie protein. It is possible that these changes in NPY-ergic mechanisms may underlie some of the central symptoms associated with the prion disease. (ABSTRACT TRUNCATED)