Neuropeptide Y (NPY) modulates oxidative burst and nitric oxide production in carrageenan-elicited granulocytes from rat air pouch

We studied the effects of neuropeptide Y (NPY) and NPY-related receptor specific peptides on functions of carrageenan-elicited granulocytes in vitro and ability of NPY to modulate carrageenan-induced air pouch inflammation in rats in vivo. Anti-inflammatory effect of NPY comprises reduced granulocyte accumulation into the air pouch, to some extent attenuation of phagocytosis, attained via Y1 receptor, and considerable decrease in peroxide production, albeit mediated via Y2 and Y5 receptors activation. Conversely, NPY increases nitric oxide production and this potentiation is mediated via Y1 receptor. It is concluded that NPY Y1 and Y2/Y5 receptors’ interaction participates in NPY-induced modulation of granulocyte functions related to inflammation.     

Receptor binding profiles of NPY analogues and fragments in different tissues and cell lines

To investigate receptor selectivity and possible species selectivity of a number of NPY analogues and fragments, receptor binding studies were performed using cell lines and membranes of several species. NPY displays 4–25-fold higher affinity for the Y₂ receptor than for the Y₁ receptor. The affinity of [Leu³¹,Pro³⁴]NPY is 7–60-fold higher for the Y₁ receptor when compared with the Y₂ subtype. Species selectivity within the Y₂ receptors is demonstrated by PYY(3–36), NPY(2–36), NPY(22–36), and NPY(26–36). It is shown that NPY(22–36) is species selective for the human Y₂ subtype (K_i of 0.3 nM) compared with the rabbit and rat Y₂ receptor (K_i of 2 and 10 nM, respectively). PYY(3–36) displays highest affinity for the human and rabbit Y₂ subtype (K_i of 0.03 and 0.17 nM). The screening of NPY analogues and fragments revealed that highest affinity for the human Y₂ receptor is shown by NPY(2–36) and PYY(3–36). In addition, PYY(3–36) and NPY(2–36) are not only subtype selective, but also species selective.     

Unexpected high density of neuropeptide Y Y1 receptors in the guinea pig spleen

Receptors for neuropeptide Y (NPY) and peptide YY (PYY) have been extensively characterized in the brain. Less is known about NPY receptor subtypes in the spleen, though it is well established that NPY produces vascular contraction in this tissue. In the present study, we found an unusually high density of Y₁ receptors in the guinea pig spleen. These receptors are localized to the red pulp and exhibit a pharmacology that is consistent with the Y₁ receptor. On the other hand, only very low densities for Y₂ receptors were observed. Therefore, the guinea pig spleen may be a ideal tissue for further study of the role of Y₁ receptors in cardiovascular and immune function.     

Autoradiographic reevaluation of the binding properties of 125I-[Leu31,Pro34]peptide YY and 125I-peptide YY3-36 to neuropeptide Y receptor subtypes in rat forebrain

125I-[Leu31,Pro34]peptide YY (PYY) and 125I-PYY3-36, initially described as selective neuropeptide Y Y1 and Y2 receptor ligands, respectively, were recently shown to label also Y4 and Y5 receptors. We used receptor autoradiography to assess whether these ligands can be reliably used to investigate the various neuropeptide Y receptors in rat forebrain. In most of the brain regions examined (in coronal sections at the level of dorsal hippocampus), specific 125I-[Leu31,Pro34]PYY binding was completely inhibited by 1 microM BIBP-3226, a selective Y1 receptor ligand, but unaffected by 10 nM rat pancreatic polypeptide, selectively inhibiting Y4 receptors, suggesting that Y4 receptors are present in negligible numbers compared with Y1 receptors in the areas examined. Significant numbers of BIBP-3226-insensitive 125I-[Leu31,Pro34]PYY binding sites were measured in the CA3 subfield of the hippocampus only, possibly representing Y5 receptors. 125I-PYY3-36 binding was unchanged by 1 microM BIBP-3226, whereas a population of 125I-PYY3-36 binding sites was sensitive to 100 nM [Leu31,Pro34]neuropeptide Y, likely representing Y5 receptors. The possibility of distinguishing between Y2 and Y5 receptors using 125I-PYY3-36 as radioligand was validated by their different regional distribution and their distinct changes 24 h after kainate seizures, i.e., binding to Y5 receptors was selectively decreased in the outer cortex, whereas binding to Y2 receptors was enhanced in the hippocampus. Thus, the use of selective unlabeled compounds is required for distinguishing the various receptor subtypes labeled by 125I-[Leu31,Pro34]PYY and 125I-PYY3-36 in rat brain tissue.     

Modeling of Neuropeptide Receptors Y1, Y4, Y5, and Docking Studies with Neuropeptide Antagonist Analogues: Implications for Selectivity

Abstract

Neuropeptide Y (NPY), receptors belong to the G-protein coupled receptor superfamily. NPY mediates several physiological responses, such as blood pressure, food intake, sedation. These actions of NPY are mediated by six receptor subtypes denoted as Y₁-Y₅ and y₆. Modeling of receptor subtypes and binding site identification is an important step in developing new therapeutic agents. We have attempted to model the three NPY receptor types, Y1, Y4, and Y5 using homology modeling and threading methods. The models are consistent with previously reported experimental evidence. To understand the interaction and selectivity of NPY analogues with different neuropeptide receptors, docking studies of two neuropeptide analogues (BVD10 and BVD15) with receptors Y1 and Y4 were carried out. Results of the docking studies indicated that the interaction of ligands BVD10 and BVD15 with Y1 and Y4 receptors are different. These results were evaluated for selectivity of peptide analogues BVD10 and BVD15 towards the receptors.     

Identification of positron emission tomography ligands for NPY Y5 receptors in the brain

A series of trans-3-oxospiro[(aza)isobenzofuran-1(3H),1′-cyclohexane]-4′-carboxamide derivatives were synthesized and profiled for NPY Y5 binding affinity, brain and CSF penetrability in rats, and susceptibility to human and mouse P-glycoprotein transporters in order to develop a PET ligand. Compound 12b exhibited an acceptable profile for a PET ligand, and [¹¹C]12b was successfully utilized in clinical settings as a Y5 PET ligand.     

神经肽Y及其受体Y1、Y2对痛觉调制的研究进展

神经肽Y（neuropeptide Y,NPY）是一种由36个氨基酸残基组成的肽类激素,属胰多肽家族,广泛分布于中枢及外周神经组织的神经元中。NPY主要参与摄食行为、心血管活动、垂体分泌等生理功能的调节。NPY还参与了痛觉调制。NPY受体有Y1、Y2、Y3、Y4、Y5和Y6六种亚型。目前对Y1受体和Y2受体的研究较多,显示Y1受体和Y2受体参与痛觉调制。但现在对NPY在痛觉中的具体作用机制还不清楚。该文对NPY及其Y1受体、Y2受体在痛觉调制中的作用作一概述。     

Regulation of Neuropeptide Y Release by Neuropeptide Y Receptor Ligands and Calcium Channel Antagonists in Hypothalamic Slices

Neuropeptide Y (NPY) is an important regulator of energy balance in mammals through its orexigenic, antithermogenic, and insulin secretagogue actions. We investigated the regulation of endogenous NPY release from rat hypothalamic slices by NPY receptor ligands and calcium channel antagonists. High-potassium stimulation (60 mM) of the slices produced a calcium-dependent threefold increase in NPY release above basal release. The Y2 receptor agonists NPY(13-36) and N-acetyl[Leu28,Leu31]NPY(24-36), the Y4 agonist rat pancreatic polypeptide (rPP), and the Y4/Y5 agonist human pancreatic polypeptide (hPP) significantly reduced both basal and stimulated NPY release. NPY(13-36)-induced reduction of NPY release could be partially prevented in the presence of the weak Y2 antagonist T4-[NPY(33-36)]4, whereas the hPP- and rPP-induced inhibition of release was not affected by the Y5 antagonist CGP71683A or the Y1 antagonist BIBP3226. The selective Y1, Y2, and Y5 antagonists had no effect on either basal or potassium-stimulated release when administered alone. The calcium channel inhibitors omega-conotoxin GVIA (N-type), omega-agatoxin TK (P/Q-type), and omega-conotoxin MVIIC (Q-type) all significantly inhibited potassium-stimulated NPY release, without any effect on basal release, whereas nifedipine had no effect on either basal or stimulated release. Addition of both omega-conotoxin GVIA and omega-agatoxin TK together completely inhibited the potassium-stimulated release. In conclusion, we have demonstrated that NPY release from hypothalamic slices is calcium-dependent, involving N-, P-, and Q-type calcium channels. NPY release is also inhibited by Y2 agonists and rPP/hPP, suggesting that Y2 and Y4 receptors may act as autoreceptors on NPY-containing nerve terminals.     

Reduced Neuropeptide Y Concentrations in Suicide Brain

Neuropeptide Y (NPY) was measured in postmortem brain tissue from victims of suicide and from individuals dying a sudden natural or accidental death (controls). Concentrations of NPY-immunoreactivity were measured by radioimmunoassay in frontal cortex (BA 10), temporal cortex (BA 22), caudate nucleus, and cerebellum. Concentrations of NPY-immunoreactivity were significantly lower in postmortem frontal cortex (-14%) and caudate nucleus (-27%) from suicide victims compared with age-matched controls. A subgroup of suicides with evidence of a history of depression revealed more robust reductions in concentrations of NPY-immunoreactivity in frontal cortex and caudate nucleus, as did four individuals who died from natural causes and also were described as having a possible history of depression. Concentrations of NPY-immunoreactivity in temporal cortex and cerebellum from victims of suicide or from the subgroup of subjects with a possible history of depression were not significantly different from those of age-matched controls. We suggest there is a deficit in the brain NPY system leading to region-specific reductions in peptide concentrations in subjects who have a history of depression.     

下丘脑腹内侧核Orexin-1及其受体对大鼠胃酸分泌的影响及其机制

目的:探讨下丘脑腹内侧核Orexin-1及其受体对大鼠胃酸分泌的影响及其机制。方法:大鼠麻醉后侧脑室及VMH置管,大鼠分组后分别VMH注射orexin-A、[Pro~(34)]-酪酪肽、[c PP1-7、NPY~(19-23)、Ala~(31)、Aib~(32)、Gln~(34)]胰多肽;腹腔注射SB-334867;皮下注射阿托品;侧脑室微量注射GR-231118、CGP-71683。给药结束后使用幽门结扎模型检测大鼠的胃酸分泌。结果:OXA能够促进胃酸分泌,且呈量效依赖关系。腹腔注射SB-334867能够抑制胃酸分泌,且呈量效依赖关系;SB-334867能够抑制orexin-A对胃酸分泌的促进作用;阿托品不但能够抑制胃酸分泌并且还能够完全阻断OXA的促胃酸分泌作用。侧脑室微量注射GR-231118或CGP-71683胃酸及胃液量减少,呈量效依赖关系,并且能够完全阻断OXA的促胃酸分泌作用。VMH内微量注射[cPP~(1-7),NPY~(19-23),Ala~(31),Aib~(32),Gln~(34)]胰多肽胃酸分泌增多,且呈量效依赖关系。结论:Orexin-A能够作用于下丘脑VMH促进胃酸分泌,orexin受体、Y1和Y5受体以及迷走神经系统均参与该过程。     

Increased food intake by neuropeptide Y is due to an increased motivation to eat

Neuropeptide Y (NPY), administered intracerebroventricularly, is a potent orexigenic agent. To determine if NPY-induced eating represented an increase in motivation to eat (e.g., hunger) rather than pathological or stimulus-bound eating, we determined its effect on eating in three paradigms, including lever press, appetitive passive avoidance and quinine-adulterated milk. NPY-injected mice consumed more milk when required to work for it in a lever press apparatus and tolerated shock to the tongue for drinking milk. Increasing the dose of NPY also allowed mice to overcome a taste aversion for quinine-adulterated milk. Overall, these studies support the hypothesis that NPY causes a specific increase in the motivation to eat, rather than nonspecific or stimulus-bound behavior.     

Neuropeptide Y (NPY) and depression: from animal studies to the human condition

Neuropeptide Y (NPY) is widely distributed throughout the central nervous system (CNS) and is one of the most conserved peptides in evolution, suggesting an important role in the regulation of basic physiological functions. In addition, both pre-clinical and clinical evidence have suggested that NPY, together with its receptors, may have a direct implication in several psychiatric disorders, including depression and related illnesses. NPY-like immunoreactivity and NPY receptors are expressed throughout the brain, with varying concentrations being found throughout the limbic system. Such brain structures have been repeatedly implicated in the modulation of emotional processing, as well as in the pathogenesis of depressive disorders. This review will concentrate on the distribution of NPY, its receptors, and the putative role played by this peptide in depressive illness based on both pre-clinical and clinical evidence.     

CGRP和NPY 在大鼠股骨闭合骨折愈合不同阶段的变化及意义

目的:探讨交感神经分泌的神经肽Y(NPY)和感觉神经分泌的钙基因相关肽(CGRP)在体内骨折愈合的不同阶段的变化及意义。方法:选择6-8月龄的雄性大鼠,建立大鼠的股骨闭合骨折模型,术后2、4、8、12周取材。进行扫描电镜,免疫组织荧光染色和血清Elisa检测。结果:1骨折愈合不同时期感觉神经肽类物质CGRP和交感神经肽类物质NPY都有表达,且其含量有先增加后减少的趋势,并在骨折后8周含量达到最高。2骨折愈合不同阶段的大鼠血清感觉神经肽类物质CGRP和交感神经肽类物质NPY均呈上升趋势,差异有统计学意义(P0.05),且NPY的含量比CGRP的含量高。骨折后2-4周,CGRP含量增加较快;骨折后4-8周NPY含量增加较快。结论:骨折愈合的不同阶段,感觉神经肽类物质CGRP和交感神经肽类物质NPY含量先升后降,对不同阶段的骨形成及骨吸收产生影响。     

Neuropeptide Y receptors activation protects rat retinal neural cells against necrotic and apoptotic cell death induced by glutamate

It has been claimed that glutamate excitotoxicity might have a role in the pathogenesis of several retinal degenerative diseases, including glaucoma and diabetic retinopathy. Neuropeptide Y (NPY) has neuroprotective properties against excitotoxicity in the hippocampus, through the activation of Y₁, Y₂ and/or Y₅ receptors. The principal objective of this study is to investigate the potential protective role of NPY against glutamate-induced toxicity in rat retinal cells (in vitro and in an animal model), unraveling the NPY receptors and intracellular mechanisms involved. Rat retinal neural cell cultures were prepared from newborn Wistar rats (P3-P5) and exposed to glutamate (500 μM) for 24 h. Necrotic cell death was evaluated by propidium iodide (PI) assay and apoptotic cell death using TUNEL and caspase-3 assays. The cell types present in culture were identified by immunocytochemistry. The involvement of NPY receptors was assessed using selective agonists and antagonists. Pre-treatment of cells with NPY (100 nM) inhibited both necrotic cell death (PI-positive cells) and apoptotic cell death (TUNEL-positive cells and caspase 3-positive cells) triggered by glutamate, with the neurons being the cells most strongly affected. The activation of NPY Y₂, Y₄ and Y₅ receptors inhibited necrotic cell death, while apoptotic cell death was only prevented by the activation of NPY Y₅ receptor. Moreover, NPY neuroprotective effect was mediated by the activation of PKA and p38K. In the animal model, NPY (2.35 nmol) was intravitreally injected 2 h before glutamate (500 nmol) injection into the vitreous. The protective role of NPY was assessed 24 h after glutamate (or saline) injection by TUNEL assay and Brn3a (marker of ganglion cells) immunohistochemistry. NPY inhibited the increase in the number of TUNEL-positive cells and the decrease in the number of Brn3a-positive cells induced by glutamate. In conclusion, NPY and NPY receptors can be considered potential targets to treat retinal degenerative diseases, such as glaucoma and diabetic retinopathy.     

Determination of agmatine in brain and plasma using high-performance liquid chromatography with fluorescence detection

Decarboxylated arginine, agmatine, is a neurotransmitter candidate for imidazoline receptors. A method is described to measure agmatine in rat brain and human plasma by isocratic high-performance liquid chromatography (HPLC) with flourescence detection and o-phthalaldehyde derivatization. Quantitation is based on the method of additions of internal agmatine spikes. This assay has sensitivity in the low picomole range and a detection limitof 100 fmol. The correlation coefficient for the agmatine standard curve was 0.999±0.001 S.D., and intra- and inter-assay C.V.s were less than 8%. The accuracy of our isocratic method compared favorably with a gradient HPLC protocol, originally developed for bacterial agmatine, which we modified for use with tissues. Agmatine concentrations in rat brain were proportioned similarly to the regional distribution of imidazoline-1 receptors. These methods can be used as reliable research tools in various biological samples.