Mitogenic actions of neuropeptide Y in vascular smooth muscle cells: synergetic interactions with the beta-adrenergic system

Neuropeptide Y in cancer-biological functions and potential clinical implications

Neuropeptide Y (NPY) is a sympathetic neurotransmitter widely distributed in the peripheral and central nervous system, affecting many physiological functions. Consequently, dysregulation of the NPY system contributes to numerous pathological disorders, including stress, obesity, and cancer. The pleiotropic functions of NPY in humans are mediated by G protein-coupled receptors (Y1R, Y2R, Y5R), which activate several signaling pathways and thereby regulate cell growth, differentiation, apoptosis, proliferation, angiogenesis, and metabolism. These activities of NPY are highly relevant to tumor biology and known hallmarks of cancer, including sustained proliferative potential, resisting cell death, angiogenesis, invasion, and metastases. In this comprehensive review, we describe the cellular functions of NPY and discuss its role in cancer pathobiology, as well as provide the current state of knowledge pertaining to NPY and its receptors in various cancer types. Moreover, we focus on potential clinical applications targeting the NPY system, such as its role as a prognostic and predictive factor, as well as its utility in cancer diagnostics, imaging, and treatment. Altogether, growing evidence supports the significant role of the NPY system in tumor pathobiology and implicates its potential therapeutic and diagnostic value in modern oncology.

Neuropeptides in Cancer: Friend and Foe?

Neuropeptides are small regulatory molecules found throughout the body, most notably in the nervous, cardiovascular, and gastrointestinal systems. They serve as neurotransmitters or hormones in the regulation of diverse physiological processes. Cancer cells escape normal growth control mechanisms by altering their expression of growth factors, receptors, or intracellular signals, and neuropeptides have recently been recognized as mitogens in cancer growth and development. Many neuropeptides and their receptors exist in multiple subtypes, coupling with different downstream signaling pathways and playing distinct roles in cancer progression. The consideration of neuropeptide/receptor systems as anticancer targets is already leading to new biological and diagnostic knowledge that has the potential to enhance the understanding and treatment of cancer. In this review, recent discoveries regarding neuropeptides in a wide range of cancers, emphasizing their mechanisms of action, signaling cascades, regulation, and therapeutic potential, are discussed. Current technologies used to manipulate and analyze neuropeptides/receptors are described. Applications of neuropeptide analogs and their receptor inhibitors in translational studies and radio-oncology are rapidly increasing, and the possibility for their integration into therapeutic trials and clinical treatment appears promising.

Immunomodulatory Role of Neuropeptides in the Cornea

The transparency of the cornea along with its dense sensory innervation and resident leukocyte populations make it an ideal tissue to study interactions between the nervous and immune systems. The cornea is the most densely innervated tissue of the body and possesses both immune and vascular privilege, in part due to its unique repertoire of resident immune cells. Corneal nerves produce various neuropeptides that have a wide range of functions on immune cells. As research in this area expands, further insights are made into the role of neuropeptides and their immunomodulatory functions in the healthy and diseased cornea. Much remains to be known regarding the details of neuropeptide signaling and how it contributes to pathophysiology, which is likely due to complex interactions among neuropeptides, receptor isoform-specific signaling events, and the inflammatory microenvironment in disease. However, progress in this area has led to an increase in studies that have begun modulating neuropeptide activity for the treatment of corneal diseases with promising results, necessitating the need for a comprehensive review of the literature. This review focuses on the role of neuropeptides in maintaining the homeostasis of the ocular surface, alterations in disease settings, and the possible therapeutic potential of targeting these systems.

Hypoxia-activated neuropeptide Y/Y5 receptor/RhoA pathway triggers chromosomal instability and bone metastasis in Ewing sarcoma

Adverse prognosis in Ewing sarcoma (ES) is associated with the presence of metastases, particularly in bone, tumor hypoxia and chromosomal instability (CIN). Yet, a mechanistic link between these factors remains unknown. We demonstrate that in ES, tumor hypoxia selectively exacerbates bone metastasis. This process is triggered by hypoxia-induced stimulation of the neuropeptide Y (NPY)/Y5 receptor (Y5R) pathway, which leads to RhoA over-activation and cytokinesis failure. These mitotic defects result in the formation of polyploid ES cells, the progeny of which exhibit high CIN, an ability to invade and colonize bone, and a resistance to chemotherapy. Blocking Y5R in hypoxic ES tumors prevents polyploidization and bone metastasis. Our findings provide evidence for the role of the hypoxia-inducible NPY/Y5R/RhoA axis in promoting genomic changes and subsequent osseous dissemination in ES, and suggest that targeting this pathway may prevent CIN and disease progression in ES and other cancers rich in NPY and Y5R.

Ewing sarcoma tumour cells frequently metastasize to the bone but the molecular mechanisms governing this process are not well understood. Here, the authors show that neuropeptide Y/Y5 receptor pathway is activated in the hypoxic tumour microenvironment, which results in cytokinesis defects and chromosomal instability, leading to bone invasion.

Current Insights Into the Role of Neuropeptide Y in Skin Physiology and Pathology

Neuropeptide Y is widely distributed within the body and has long been implicated as a contributor to skin disease based on the correlative clinical data. However, until recently, there have been few empirical investigations to determine whether NPY has a pathophysiological role in the skin. Due to appearance-altering phenotypes of atopic dermatitis, psoriasis, and vitiligo, those suffering from these diseases often face multiple forms of negative social attention. This often results in psychological stress, which has been shown to exacerbate inflammatory skin diseases - creating a vicious cycle that perpetuates disease. This has been shown to drive severe depression, which has resulted in suicidal ideation being a comorbidity of these diseases. Herein, we review what is currently known about the associations of NPY with skin diseases and stress. We also review and provide educated guessing what the effects NPY can have in the skin. Inflammatory skin diseases can affect physical appearance to have significant, negative impacts on quality of life. No cure exists for these conditions, highlighting the need for identification of novel proteins/neuropetides, like NPY, that can be targeted therapeutically. This review sets the stage for future investigations into the role of NPY in skin biology and pathology to stimulate research on therapeutic targeting NPY signaling in order to combat inflammatory skin diseases.

Regulation of neuropeptide Y in body microenvironments and its potential application in therapies: a review

Neuropeptide Y (NPY), one of the most abundant neuropeptides in the body, is widely expressed in the central and peripheral nervous systems and acts on the cardiovascular, digestive, endocrine, and nervous systems. NPY affects the nutritional and inflammatory microenvironments through its interaction with immune cells, brain-derived trophic factor (BDNF), and angiogenesis promotion to maintain body homeostasis. Additionally, NPY has great potential for therapeutic applications against various diseases, especially as an adjuvant therapy for stem cells. In this review, we discuss the research progress regarding NPY, as well as the current evidence for the regulation of NPY in each microenvironment, and provide prospects for further research on related diseases.

Neuropeptide Y nerve paracrine regulation of prostate cancer oncogenesis and therapy resistance

BACKGROUND

Nerves are key factors in prostate cancer (PCa) progression. Here, we propose that neuropeptide Y (NPY) nerves are key regulators of cancer-nerve interaction.

METHODS

We used in vitro models for NPY inhibition studies and subsequent metabolomics, apoptotic and migration assays, and nuclear transcription factor-κB (NF-κB) translocation studies. Human naïve and radiated PCa tissues were used for NPY nerve density biomarker studies. Tissues derived from a Botox denervation clinical trial were used to corroborate metabolomic changes in humans.

RESULTS

Cancer cells increase NPY positive nerves in vitro and in preneoplastic human tissues. NPY-specific inhibition resulted in increased cancer apoptosis, decreased motility, and energetic metabolic pathway changes. A comparison of metabolomic response in NPY-inhibited cells with the transcriptome response in human PCa patients treated with Botox showed shared 13 pathways, including the tricarboxylic acid cycle. We identified that NF-κB is a potential NPY downstream mediator. Using in vitro models and tissues derived from a previous human chemical denervation study, we show that Botox specifically, but not exclusively, inhibits NPY in cancer. Quantification of NPY nerves is independently predictive of PCa-specific death. Finally, NPY nerves might be involved in radiation therapy (RT) resistance, as radiation-induced apoptosis is reduced when PCa cells are cocultured with dorsal root ganglia/nerves and NPY positive nerves are increased in prostates of patients that failed RT.

CONCLUSION

These data suggest that targeting the NPY neural microenvironment may represent a therapeutic approach for the treatment of PCa and resistance through the regulation of multiple oncogenic mechanisms.

Isolation, culturing and gene expression profiling of inner mass cells from stable and vulnerable carotid atherosclerotic plaques

The connective tissue components that form the atherosclerotic plaque body are produced by the plaque inner mass cells (PIMC), located inside the plaque. We report an approach to isolate and culture cells from the connective tissue of stable and vulnerable human atherosclerotic plaques based on elimination of non-connective tissue cells such as blood and non-plaque intima cells with a lysis buffer. The resulting plaque cells were characterized by growth capacity, morphology, transcriptome profiling and specific protein expression. Plaque cells slowly proliferated for up to three passages unaffected by the use of proliferation stimulants or changes of culture media composition. Stable plaques yielded more cells than vulnerable ones. Plaque cell cultures also contained several morphological cellular types. RNA-seq profiles of plaque cells were different from any of the cell types known to be involved in atherogenesis. The expression of the following proteins was observed in cultured plaque cells: smooth muscle cells marker α-SMA, macrophage marker CD14, extracellular matrix proteins aggrecan, fibronectin, neovascularisation markers VEGF-A, CD105, cellular adhesion receptor CD31 and progenitor/dedifferentiation receptor CD34. Differential expression of several notable transcripts in cells from stable and vulnerable plaques suggests the value of plaque cell culture studies for the search of plaque vulnerability markers.

Neuropeptide Y receptor interactions regulate its mitogenic activity

Neuropeptide Y (NPY) is a multifunctional neurotransmitter acting via G protein-coupled receptors - Y1R, Y2R and Y5R. NPY activities, such as its proliferative effects, are mediated by multiple receptors, which have the ability to dimerize. However, the role of this receptor interplay in NPY functions remains unclear. The goal of the current study was to identify NPY receptor interactions, focusing on the ligand-binding fraction, and determine their impact on the mitogenic activity of the peptide. Y1R, Y2R and Y5R expressed in CHO-K1 cells formed homodimers detectable on the cell surface by cross-linking. Moreover, Y1R and Y5R heterodimerized, while no Y2R/Y5R heterodimers were detected. Nevertheless, Y5R failed to block internalization of its cognate receptor in both Y1R/Y5R and Y2R/Y5R transfectants, indicating Y5R transactivation upon stimulation of the co-expressed receptor. These receptor interactions correlated with an augmented mitogenic response to NPY. In Y1R/Y5R and Y2R/Y5R transfectants, the proliferative response started at picomolar NPY concentrations, while nanomolar concentrations were needed to trigger proliferation in cells transfected with single receptors. Thus, our data identify direct and indirect heterotypic NPY receptor interactions as the mechanism amplifying its activity. Understanding these processes is crucial for the design of treatments targeting the NPY system.

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.

Neuropeptide Y and its receptors in ventricular endocardial endothelial cells

Endocardial endothelial cells (EECs) constitute an important component of the heart. These cells form a monolayer that covers the cavities of the right (EECRs) and left (EECLs) ventricles. They play an important role in cardiac excitation-contraction coupling via their secretion of cardioactive factors such as neuropeptide Y (NPY). They also contribute to cardiac pathology such as arrhythmia, hypertrophy, and heart failure. Differences between EECRs and EECLs contribute to tuning of circulating factors at the entry and exit of the ventricles. NPY, via activation of its receptors, modulates the excitation-secretion coupling of EECs, thus, indirectly modulating cardiac function and remodeling.

Different effects of neuropeptide Y on proliferation of vascular smooth muscle cells via regulation of Geminin

The proliferation-promoting effect of neuropeptide Y (NPY) always functions in low-serum-cultured vascular smooth muscle cells (VSMCs), and the phenotypic switch of VSMCs is regulated by concentrations of serum. Whether the property of the NPY proliferative effect in VSMCs relies on phenotype of VSMCs is unclear. We aimed to explore the role of NPY on proliferation of different VSMC phenotypes in the pathogenesis of atherosclerosis. By stimulating A10 cells with 200 nM NPY in 0.5 or 10% serum, 3H-thymidine and 5-ethynyl-2'-deoxyuridine (EdU) and CCK8 measurements were used to detect VSMC proliferation. RT-PCR and Flow cytometry were performed to detect the factors involved in different properties of the NPY proliferative effect in VSMCs. Instead of facilitating proliferation, NPY had no significant effect on the growth of VSMCs when cultured in 10% serum (VSMCs stayed at synthetic states). The underlying mechanism may be involved in down-regulation of Y1 receptor (P < 0.05 vs. Vehicle) and up-regulation of Geminin (P < 0.05 vs. Vehicle) in 10% serum-cultured VSMCs co-incubated with 200 nM NPY. Besides, modulation of Geminin was effectively blocked by the Y1 receptor antagonist. The stimulation of NPY on proliferation of VSMCs could be a double-edged sword in the development of atherosclerosis and thus provides new knowledge for therapy of atherosclerosis.

Neuropeptide Y as a Biomarker and Therapeutic Target for Neuroblastoma

Neuroblastoma (NB) is a pediatric malignant neoplasm of sympathoadrenal origin. Challenges in its management include stratification of this heterogeneous disease and a lack of both adequate treatments for high-risk patients and noninvasive biomarkers of disease progression. Our previous studies have identified neuropeptide Y (NPY), a sympathetic neurotransmitter expressed in NB, as a potential therapeutic target for these tumors by virtue of its Y5 receptor (Y5R)-mediated chemoresistance and Y2 receptor (Y2R)-mediated proliferative and angiogenic activities. The goal of this study was to determine the clinical relevance and utility of these findings. Expression of NPY and its receptors was evaluated in corresponding samples of tumor RNA, tissues, and sera from 87 patients with neuroblastic tumors and in tumor tissues from the TH-MYCN NB mouse model. Elevated serum NPY levels correlated with an adverse clinical presentation, poor survival, metastasis, and relapse, whereas strong Y5R immunoreactivity was a marker of angioinvasive tumor cells. In NB tissues from TH-MYCN mice, high immunoreactivity of both NPY and Y5R marked angioinvasive NB cells. Y2R was uniformly expressed in undifferentiated tumor cells, which supports its previously reported role in NB cell proliferation. Our findings validate NPY as a therapeutic target for advanced NB and implicate the NPY/Y5R axis in disease dissemination. The correlation between elevated systemic NPY and NB progression identifies serum NPY as a novel NB biomarker.

GPCRs of adrenal chromaffin cells & catecholamines: The plot thickens

The circulating catecholamines (CAs) epinephrine (Epi) and norepinephrine (NE) derive from two major sources in the whole organism: the sympathetic nerve endings, which release NE on effector organs, and the chromaffin cells of the adrenal medulla, which are cells that synthesize, store and release Epi (mainly) and NE. All of the Epi in the body and a significant amount of circulating NE derive from the adrenal medulla. The secretion of CAs from adrenal chromaffin cells is regulated in a complex way by a variety of membrane receptors, the vast majority of which are G protein-coupled receptors (GPCRs), including adrenergic receptors (ARs), which act as "presynaptic autoreceptors" in this regard. There is a plethora of CA-secretagogue signals acting on these receptors but some of them, most notably the α2ARs, inhibit CA secretion. Over the past few years, however, a few new proteins present in chromaffin cells have been uncovered to participate in CA secretion regulation. Most prominent among these are GRK2 and β-arrestin1, which are known to interact with GPCRs regulating receptor signaling and function. The present review will discuss the molecular and signaling mechanisms by which adrenal chromaffin cell-residing GPCRs and their regulatory proteins modulate CA synthesis and secretion. Particular emphasis will be given to the newly discovered roles of GRK2 and β-arrestins in these processes and particular points of focus for future research will be highlighted, as well.

Neuropeptide Y is an angiogenic factor in cardiovascular regeneration

In diabetic cardiomyopathy, there is altered angiogenic signaling and increased oxidative stress. As a result, anti-angiogenic and pro-inflammatory pathways are activated. These disrupt cellular metabolism and cause fibrosis and apoptosis, leading to pathological remodeling. The autonomic nervous system and neurotransmitters play an important role in angiogenesis. Therapies that promote angiogenesis may be able to relieve the pathology in these disease states. Neuropeptide Y (NPY) is the most abundantly produced and expressed neuropeptide in the central and peripheral nervous systems in mammals and plays an important role in promoting angiogenesis and cardiomyocyte remodeling. It produces effects through G-protein-coupled Y receptors that are widely distributed and also present on the myocardium. Some of these receptors are also involved in diseased states of the heart. NPY has been implicated as a potent growth factor, causing cell proliferation in multiple systems while the NPY3-36 fragment is selective in stimulating angiogenesis and cardiomyocyte remodeling. Current research is focusing on developing a drug delivery mechanism for NPY to prolong therapy without having significant systemic consequences. This could be a promising innovation in the treatment of diabetic cardiomyopathy and ischemic heart disease.

Neuropeptide Y (NPY) in tumor growth and progression: Lessons learned from pediatric oncology

Neuropeptide Y (NPY) is a sympathetic neurotransmitter with pleiotropic actions, many of which are highly relevant to tumor biology. Consequently, the peptide has been implicated as a factor regulating the growth of a variety of tumors. Among them, two pediatric malignancies with high endogenous NPY synthesis and release - neuroblastoma and Ewing sarcoma - became excellent models to investigate the role of NPY in tumor growth and progression. The stimulatory effect on tumor cell proliferation, survival, and migration, as well as angiogenesis in these tumors, is mediated by two NPY receptors, Y2R and Y5R, which are expressed in either a constitutive or inducible manner. Of particular importance are interactions of the NPY system with the tumor microenvironment, as hypoxic conditions commonly occurring in solid tumors strongly activate the NPY/Y2R/Y5R axis. This activation is triggered by hypoxia-induced up-regulation of Y2R/Y5R expression and stimulation of dipeptidyl peptidase IV (DPPIV), which converts NPY to a selective Y2R/Y5R agonist, NPY(3-36). While previous studies focused mainly on the effects of NPY on tumor growth and vascularization, they also provided insight into the potential role of the peptide in tumor progression into a metastatic and chemoresistant phenotype. This review summarizes our current knowledge of the role of NPY in neuroblastoma and Ewing sarcoma and its interactions with the tumor microenvironment in the context of findings in other malignancies, as well as discusses future directions and potential clinical implications of these discoveries.

ETA and ETB receptors contribute to neuropeptide Y-induced secretion of endothelin-1 in right but not left human ventricular endocardial endothelial cells

Our recent work showed that neuropeptide Y-induced secretion of endothelin-1 (ET-1) in left and right human ventricular endocardial endothelial cells (hLEECs or hREECs respectively) via the activation of neuropeptide Y2 or Y5 receptors depending on the cell type. The aim of this study was to verify whether hLEECs or hREECs secretion of ET-1 induced by NPY is due, in part, to the activation of ETA and/or ETB receptors by the secreted ET-1. Using the technique of indirect immunofluorescence coupled to real 3-D confocal microscopy, as well as ELISA, our results show that in hREECs, the NPY-induced release of ET-1 seems to be due, in part, to the activation of both ETA and ETB receptors. On the other hand, in hLEECs, ETA and ETB receptors do not contribute to the ET-1 released by NPY. Therefore, our results suggest that the NPY-induced release of ET-1 in EECRs is due to NPY receptor activation and the subsequent activation of the ETA and ETB receptors by the released ET-1. However, the release of ET-1 by NPY in hLEECs is mainly due to NPY receptor activation. Furthermore, this secretory process of ET-1 is different between the right and left ventricular cells and highlights the important tuning roles that right and left ventricular EECs possess as well as their contribution to the physiological and pathophysiological states of the underlying heart muscle.

High neuropeptide Y release associates with Ewing sarcoma bone dissemination - in vivo model of site-specific metastases

Ewing sarcoma (ES) develops in bones or soft tissues of children and adolescents. The presence of bone metastases is one of the most adverse prognostic factors, yet the mechanisms governing their formation remain unclear. As a transcriptional target of EWS-FLI1, the fusion protein driving ES transformation, neuropeptide Y (NPY) is highly expressed and released from ES tumors. Hypoxia up-regulates NPY and activates its pro-metastatic functions. To test the impact of NPY on ES metastatic pattern, ES cell lines, SK-ES1 and TC71, with high and low peptide release, respectively, were used in an orthotopic xenograft model. ES cells were injected into gastrocnemius muscles of SCID/beige mice, the primary tumors excised, and mice monitored for the presence of metastases. SK-ES1 xenografts resulted in thoracic extra-osseous metastases (67%) and dissemination to bone (50%) and brain (25%), while TC71 tumors metastasized to the lungs (70%). Bone dissemination in SK-ES1 xenografts associated with increased NPY expression in bone metastases and its accumulation in bone invasion areas. The genetic silencing of NPY in SK-ES1 cells reduced bone degradation. Our study supports the role for NPY in ES bone invasion and provides new models for identifying pathways driving ES metastases to specific niches and testing anti-metastatic therapeutics.

Neuropeptide Y Stimulates Proliferation and Migration of Vascular Smooth Muscle Cells from Pregnancy Hypertensive Rats via Y1 and Y5 Receptors

The increased proliferation and migration of vascular smooth muscle cells (VSMCs) play important roles in pathophysiological remodeling of arteries during hypertension in pregnancy. However, the mechanisms involved in this process remain unclear. We hypothesized that Neuropeptide Y (NPY), which is a potent mitogenic peptide, participates in modulating proliferation and migration of VSMCs during hypertension in pregnancy. Using pregnant hypertensive rats, induced by intraperitoneal injection of L-nitro-arginine methylester (L-NAME), the plasma concentration of NPY was detected. Open angle, which reflects the non-uniform remodeling with high sensitivity, was used to detect the pathophysiological vascular remodeling in vivo. The results revealed that NPY concentration and artery open angle were both significantly increased in rats with hypertension in pregnant. The underlying mechanism of elevated NPY on vascular remodeling were further analyzed by using cultured VSMCs in vitro. In cultured VSMCs, NPY most effectively stimulated the migration and proliferation of VSMCs at 10^-6 mol/L, similar to the plasma concentration in L-NAME hypertension in pregnant rats. NPY up-regulated the expressions of both Y1 and Y5 receptors, increased the phosphorylations of STAT3 on Tyr705 and Ser727 residues, and induced the expression of c-Fos. The NPY-induced VSMCs proliferation was reduced by Y5 receptor antagonist, and fully blocked by combinations with other antagonist, such as Y2+Y5, Y1+Y5, and Y1+Y2+Y5. In contrast, the NPY-induced VSMC migration was blocked by either Y receptor antagonist or any combination of Y receptor antagonists. These results suggest that the elevated plasma concentration of NPY during hypertension in pregnancy may induce VSMC proliferation mainly via Y5 receptor, which subsequently modulate STAT3 and c-Fos signaling pathways to result in the vascular remodeling. These results also suggest that NPY mainly acts on VSMCs in vitro via Y1, Y5 receptors and in vascular tissues in vivo via Y5 receptor.

Neuropeptide Y receptor Y5 as an inducible pro-survival factor in neuroblastoma: implications for tumor chemoresistance

Neuroblastoma (NB) is a pediatric tumor of neural crest origin with heterogeneous phenotypes. While low stage tumors carry a favorable prognosis, over 50% of high risk NB relapses after treatment with a fatal outcome. Thus, developing therapies targeting refractory NB remains an unsolved clinical problem. Brain-derived neurotrophic factor (BDNF) and its TrkB receptor are known to protect NB cells from chemotherapy-induced cell death, while neuropeptide Y (NPY), acting via its Y2 receptor (Y2R), is an autocrine proliferative and angiogenic factor crucial for maintaining NB tumor growth. Here, we show that in NB cells, BDNF stimulates the synthesis of NPY and induces expression of another one of its receptors, Y5R. In human NB tissues, the expression of NPY and Y5R positively correlated with the expression of BDNF and TrkB. Functionally, BDNF triggered Y5R internalization in NB cells, while Y5R antagonist inhibited BDNF-induced p44/42-MAPK activation and its pro-survival activity. These observations suggested TrkB-Y5R transactivation that resulted in cross-talk between their signaling pathways. Additionally, NPY and Y5R were up-regulated in a BDNF-independent manner in NB cells under pro-apoptotic conditions, such as serum deprivation and chemotherapy, as well as in cell lines and tissues derived from post-treatment NB tumors. Blocking Y5R in chemoresistant NB cells rich in this receptor sensitized them to chemotherapy-induced apoptosis and inhibited their growth in vivo by augmenting cell death. In summary, the NPY/Y5R axis is an inducible survival pathway activated in NB by BDNF or cellular stress. Upon such activation, Y5R augments the pro-survival effect of BDNF via its interactions with TrkB receptor and exerts an additional BDNF-independent anti-apoptotic effect, both of which contribute to NB chemoresistance. Therefore, the NPY/Y5R pathway may become a novel therapeutic target for patients with refractory NB, thus far an incurable form of this disease.

Platelet neuropeptide Y is critical for ischemic revascularization in mice

We previously reported that the sympathetic neurotransmitter neuropeptide Y (NPY) is potently angiogenic, primarily through its Y2 receptor, and that endogenous NPY is crucial for capillary angiogenesis in rodent hindlimb ischemia. Here we sought to identify the source of NPY responsible for revascularization and its mechanisms of action. At d 3, NPY(-/-) mice demonstrated delayed recovery of blood flow and limb function, consistent with impaired collateral conductance, while ischemic capillary angiogenesis was reduced (~70%) at d 14. This biphasic temporal response was confirmed by 2 peaks of NPY activation in rats: a transient early increase in neuronally derived plasma NPY and increase in platelet NPY during late-phase recovery. Compared to NPY-null platelets, collagen-activated NPY-rich platelets were more mitogenic (~2-fold vs. ~1.6-fold increase) for human microvascular endothelial cells, and Y2/Y5 receptor antagonists ablated this difference in proliferation. In NPY(+/+) mice, ischemic angiogenesis was prevented by platelet depletion and then restored by transfusion of platelets from NPY(+/+) mice, but not NPY(-/-) mice. In thrombocytopenic NPY(-/-) mice, transfusion of wild-type platelets fully restored ischemia-induced angiogenesis. These findings suggest that neuronally derived NPY accelerates the early response to femoral artery ligation by promoting collateral conductance, while platelet-derived NPY is critical for sustained capillary angiogenesis.

A new murine model of stress-induced complex atherosclerotic lesions

The primary purpose of this investigation was to determine whether ApoE^−/− mice, when subjected to chronic stress, exhibit lesions characteristic of human vulnerable plaque and, if so, to determine the time course of such changes. We found that the lesions were remarkably similar to human vulnerable plaque, and that the time course of lesion progression raised interesting insights into the process of plaque development. Lard-fed mixed-background ApoE^−/− mice exposed to chronic stress develop lesions with large necrotic core, thin fibrous cap and a high degree of inflammation. Neovascularization and intraplaque hemorrhage are observed in over 80% of stressed animals at 20 weeks of age. Previously described models report a prevalence of only 13% for neovascularization observed at a much later time point, between 36 and 60 weeks of age. Thus, our new stress-induced model of advanced atherosclerotic plaque provides an improvement over what is currently available. This model offers a tool to further investigate progression of plaque phenotype to a more vulnerable phenotype in humans. Our findings also suggest a possible use of this stress-induced model to determine whether therapeutic interventions have effects not only on plaque burden, but also, and importantly, on plaque vulnerability.

Neuropeptide Y (NPY): genetic variation in the human promoter alters glucocorticoid signaling, yielding increased NPY secretion and stress responses

OBJECTIVES

This study sought to understand whether genetic variation at the Neuropeptide Y (NPY) locus governs secretion and stress responses in vivo as well as NPY gene expression in sympathochromaffin cells.

BACKGROUND

The NPY is a potent pressor peptide co-released with catecholamines during stress by sympathetic axons. Genome-wide linkage on NPY secretion identified a LOD (logarithm of the odds ratio) peak spanning the NPY locus on chromosome 7p15.

METHODS

Our approach began with genomics (linkage and polymorphism determination), extended into NPY genetic control of heritable stress traits in twin pairs, established transcriptional mechanisms in transfected chromaffin cells, and concluded with observations on blood pressure (BP) in the population.

RESULTS

Systematic polymorphism tabulation at NPY (by re-sequencing across the locus: promoter, 4 exons, exon/intron borders, and untranslated regions; on 2n = 160 chromosomes of diverse biogeographic ancestries) identified 16 variants, of which 5 were common. We then studied healthy twin/sibling pairs (n = 399 individuals), typing 6 polymorphisms spanning the locus. Haplotype and single nucleotide polymorphism analyses indicated that proximal promoter variant ∇-880Δ (2-bp TG/-, Ins/Del, rs3037354) minor/Δ allele was associated with several heritable (h(2)) stress traits: higher NPY secretion (h(2) = 73 ± 4%) as well as greater BP response to environmental (cold) stress, and higher basal systemic vascular resistance. Association of ∇-880Δ and plasma NPY was replicated in an independent sample of 361 healthy young men, with consistent allelic effects; genetic variation at NPY also associated with plasma NPY in another independent series of 2,212 individuals derived from Australia twin pairs. Effects of allele -880Δ to increase NPY expression were directionally coordinate in vivo (on human traits) and in cells (transfected NPY promoter/luciferase reporter activity). Promoter -880Δ interrupts a novel glucocorticoid response element motif, an effect confirmed in chromaffin cells by site-directed mutagenesis on the transfected promoter, with differential glucocorticoid stimulation of the motif as well as alterations in electrophoretic mobility shifts. The same -880Δ allele also conferred risk for hypertension and accounted for approximately 4.5/approximately 2.1 mm Hg systolic BP/diastolic BP in a population sample from BP extremes.

CONCLUSIONS

We conclude that common genetic variation at the NPY locus, especially in proximal promoter ∇-880Δ, disrupts glucocorticoid signaling to influence NPY transcription and secretion, raising systemic vascular resistance and early heritable responses to environmental stress, eventuating in elevated resting BP in the population. The results point to new molecular strategies for probing autonomic control of the human circulation and ultimately susceptibility to and pathogenesis of cardiovascular and neuropsychiatric disease states.

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

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

Of mice and men: neuropeptide Y and its receptors are associated with atherosclerotic lesion burden and vulnerability

Neuropeptide Y (NPY), a sympathetic and platelet-derived vascular mitogen and angiogenic factor, has been implicated in atherosclerosis in animal and human genetic studies. Here we evaluate its association with human and murine atherosclerosis, and assess the role of platelet-derived NPY in lesion vulnerability. NPY immunoreactivity (NPY-ir) was measured in the platelet-poor and platelet-rich (PRP) plasmas, and NPY receptors (mitogenic Y1R and angiogenic Y2 and Y5Rs), CD26/DPPIV (a protease forming Y2/Y5-selective agonist), CD31-positive vascularity, and lesion morphology assessed by histo- and immunocyto-chemistry-in patients with peripheral artery disease (PAD) and healthy volunteers, and in lard-fed ApoE-/- mice. NPY and NPY-R immunostaining was greater in lesions from PAD patients compared to normal vessels of healthy volunteers (p < 0.001), and localized to smooth muscle cells, macrophages, and adventitial/neovascular endothelial cells. CD26/DPPIV staining co-localized with CD31-positive endothelial cells only in atherosclerotic lesions. NPY-ir in PRP (but not plasma) and vascular immunostaining was higher (p < 0.05 and 0.001, respectively) in men (not women) with PAD compared to healthy subjects. A similar gender specificity was observed in mice. PRP NPY-ir levels correlated with lesion area (p = 0.03), necrotic core area, and the necrotic core-to-lesion area ratio (p < 0.01) in male, but not female, mice. Also males with neovascularized lesions had higher PRP NPY-ir levels than those lacking lesion microvessels (p < 0.05). NPY and its Rs are up-regulated in human and murine atherosclerotic lesions suggesting pathogenic role. DPPIV expression by microvascular endothelium in atherosclerotic tissue may shift NPY's affinity toward angiogenic Y2/Y5Rs, and thus enhance angiogenesis and lesion vulnerability. Remarkably, plaque neovascularization was associated with increased NPY-ir in PRP in males but not females, suggesting that platelet NPY may be a novel mediator/marker of lesion vulnerability particularly in males, for reasons that remain to be determined. Both animal and human data suggest that NPY is an important contributor to, and platelet NPY-ir a marker of, atherosclerotic lesion burden and vulnerability but only in males, perhaps due to androgen-dependent up-regulation of NPY, previously shown in rats.

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.

Expression of trophic peptides and their receptors in chromaffin cells and pheochromocytoma

Pheochromocytomas are catecholamine-producing tumors arising from chromaffin cells of the adrenal medulla or extra-adrenal location. Along with catecholamines, tumoral cells produce and secrete elevated quantities of trophic peptides which are normally released in a regulated manner by the normal adrenal medulla. Among these peptides, the amounts of pituitary adenylate cyclase-activating polypeptide (PACAP), adrenomedullin (AM), and neuropeptide Y (NPY) are particularly high. These peptides can exert endocrine, paracrine or autocrine effects in numerous cell types. In particular, they have been shown to be involved in cell proliferation and survival, catecholamine production and secretion, and angiogenesis. Some of these processes are exacerbated in pheochromocytomas, raising the possibility of the involvement of trophic peptides. Here, we review the expression levels of NPY, PACAP, and AM and theirs receptors in chromaffin cells and pheochromocytomas, and address their possible implication in the adrenal medulla tumorigenesis and malignant development of pheochromocytomas.

Neuropeptide Y is a mediator of chronic vascular and metabolic maladaptations to stress and hypernutrition

Neuropeptide Y (NPY) is a central neuromodulator and peripheral sympathetic neurotransmitter that also has important regulatory roles in cardiovascular, neuroendocrine, immune and metabolic functions during stress. Focusing on the peripheral actions of the peptide in rodent models, we summarize recent studies from our laboratory demonstrating that stress-induced release of NPY mediates accelerated atherosclerosis/restenosis, obesity and metabolic-like syndrome, particularly when combined with a high fat, high sugar diet. In this review, we propose mechanisms of NPY's actions, its receptors and cellular substrates that increase the risk for cardiovascular and metabolic diseases when chronic stress is associated with pre-existing vascular injury and/or states of hypernutrition.

Adaptation to extreme stress: post-traumatic stress disorder, neuropeptide Y and metabolic syndrome

The prevalence rates of obesity and metabolic syndrome are on the rise in the United States. Epidemiological surveys suggest that the rates of these medical conditions are especially high among persons with psychiatric disorders, including post-traumatic stress disorder (PTSD). A variety of factors are thought to contribute to the risk for metabolic syndrome, including excessive caloric intake, decreased activity and energy expenditure, use of certain medications, stress and genetic influences. Recent research demonstrates that stress, acting through the neuropeptide Y (NPY) and glucocorticoid systems, potentiates the development of obesity and other aspects of metabolic syndrome in mice fed a high caloric, fat and sugar diet. Alterations in the NPY and glucocorticoid systems also impact behavioral adaptation to stress, as indicated by studies in animals and persons exposed to severe, life-threatening or traumatic stress. The following review examines the biology of the NPY and neuroactive steroid systems as physiological links between metabolic syndrome and PTSD, a paradigmatic neuropsychiatric stress disorder. Hopefully, understanding the function of these systems from both a translational and systems biology point of view in relation to stress will enable development of more effective methods for preventing and treating the negative physical and mental health consequences of stress.

Effects of neuropeptide Y on collateral development in a swine model of chronic myocardial ischemia

We investigated the role of neuropeptide Y (NPY), abundant in the myocardial sympathetic nervous system and endothelial cells, in angiogenesis during chronic myocardial ischemia. Adult male Yorkshire swine underwent ameroid constrictor placement on the proximal left circumflex coronary artery. After 3 weeks, an osmotic pump was placed to deliver either placebo (control, n=8) or NPY(3-36) (NPY, n=8) to the collateral dependent region. Five weeks after pump placement, after cardiac catheterization and hemodynamic assessment, the heart was harvested for analysis. NPY treated animals demonstrated increased mean arterial pressures and improved left ventricular function (+dP/dt). Cardiac catheterization demonstrated a significant increase in the blush score in the NPY group (p<0.001). Blood flow to the ischemic myocardium was not different between groups at rest or during ventricular pacing. Immunohistochemical double staining for CD-31 and smooth muscle actin demonstrated an increase in capillary and arteriole formation in NPY treated animals (p=0.02 and p<0.001). Immunoblotting showed a significant upregulation of DPPIV (p=0.009) and NPY receptors 1 (p=0.008), 2 (p=0.02) and 5 (p=0.03) in the NPY treated group. Additionally, there was significant upregulation of VEGF (p=0.04), eNOS (p=0.014), phospho-eNOS (ser1177) (p=0.02), and PDGF (p<0.001) in NPY treated group. The anti-angiogenic factors endostatin and angiostatin were significantly decreased in NPY treated animals (endostatin, p=0.03; angiostatin, p=0.04). Exogenous NPY(3-36) resulted in improved myocardial function and increased angiogenesis and arteriogenesis by stimulating growth factor, pro-angiogenic receptor upregulation, and decreasing anti-angiogenic expression, but did not increase blood flow to the ischemic myocardium. NPY may act as a good adjunct to primary agents of therapeutic angiogenesis.

Neuropeptide Y and its Y2 receptor: potential targets in neuroblastoma therapy

Neuroblastomas are pediatric tumors which develop from sympathetic precursors and express neuronal proteins, such as neuropeptide Y (NPY). NPY is a sympathetic neurotransmitter acting via multiple receptors (Y1-Y5R). Both NPY and Y2Rs are commonly expressed in neuroblastoma cell lines and tissues. The peptide secreted from neuroblastomas stimulates tumor cell proliferation and angiogenesis. Since both processes are Y2R-mediated, the goal of this study was to assess Y2R as a potential therapeutic target for neuroblastoma. In vitro, Y2R antagonist (BIIE0246) prevented activation of p44/42 MAPK induced by endogenous NPY, which resulted in decreased proliferation and induction of Bim-mediated apoptosis. Similar growth-inhibitory effects were achieved with NPY siRNA and Y2R siRNA. In vivo, Y2R antagonist significantly inhibited growth of SK-N-BE(2) and SK-N-AS xenografts, which was associated with decreased activation of p44/42 MAPK, as well as reduced proliferation (Ki67) and increased apoptosis (TUNEL). The Y2R antagonist also exerted an anti-angiogenic effect. In vitro, it reduced the proliferation of endothelial cells induced by neuroblastoma-conditioned media. Consequently, the Y2R antagonist-treated xenografts had decreased vascularization and a high degree of focal fibrosis. In human neuroblastoma tissues, the expression of Y2R was observed in both tumor and endothelial cells, while NPY was predominantly expressed in neuroblastoma cells. In summary, Y2R is a promising new target for neuroblastoma therapy affecting both cancer cells and tumor vasculature.

The effect of endogenous preproneuropeptide Y leucine 7 to proline 7 polymorphism on growth and apoptosis in primary cultured HUVECs

Neuropeptide Y (NPY) is a universally expressed neuropeptide involved in the regulation of several physiological functions. The rather common leucine7 to proline7 (L7P) polymorphism in the signal peptide of preproNPY is a functional substitution, which changes the processing and release of NPY in cells. The mutation is associated with altered lipid levels and accelerated atherosclerosis in humans. Based on previous studies, we investigated the effect of the Pro7 allele in endothelial cells, which are known to play a role in the development of atherosclerosis. Cell proliferation and apoptosis were studied in primary cultured, genotyped human umbilical vein endothelial cells (HUVECs). Our results indicate that cells with the [p.L7]+[p.P7] genotype seem to have a tendency to be more sensitive to the growth stimulating effect of NPY and less sensitive to the effect of vascular endothelial growth factor compared to cells with the [p.L7]+[p.L7] genotype. Additionally, cells with the [p.L7]+[p.P7] genotype seem to be more sensitive to apoptosis than [p.L7]+[p.L7] cells. We speculate that the L7P substitution in preproNPY might cause a state of cellular pre-senescence, leading to endothelial dysfunction. This might be one reason for the associations of the L7P polymorphism with atherosclerosis and type II diabetes found in clinical studies.

Neuropeptide Y and neurovascular control in skeletal muscle and skin

Neuropeptide Y (NPY) is a ubiquitous peptide with multiple effects on energy metabolism, reproduction, neurogenesis, and emotion. In addition, NPY is an important sympathetic neurotransmitter involved in neurovascular regulation. Although early studies suggested that the vasoactive effects of NPY were limited to periods of high stress, there is growing evidence for the involvement of NPY on baseline vasomotor tone and sympathetically evoked vasoconstriction in vivo in both skeletal muscle and the cutaneous circulation. In Sprague-Dawley rat skeletal muscle, Y(1)-receptor activation appears to play an important role in the regulation of basal vascular conductance, and this effect is similar in magnitude to the alpha(1)-receptor contribution. Furthermore, under baseline conditions, agonist and receptor-based mechanisms for Y(1)-receptor-dependent control of vascular conductance in skeletal muscle are greater in male than female rats. In skin, there is Y(1)-receptor-mediated vasoconstriction during whole body, but not local, cooling. As with the NPY system in muscle, this neural effect in skin differs between males and females and in addition, declines with aging. Intriguingly, skin vasodilation to local heating also requires NPY and is currently thought to be acting via a nitric oxide pathway. These studies are establishing further interest in the role of NPY as an important vasoactive agent in muscle and skin, adding to the complexity of neurovascular regulation in these tissues. In this review, we focus on the role of NPY on baseline vasomotor tone in skeletal muscle and skin and how NPY modulates vasomotor tone in response to stress, with the aim of compiling what is currently known, while highlighting some of the more pertinent questions yet to be answered.

Interactions of multiple signaling pathways in neuropeptide Y-mediated bimodal vascular smooth muscle cell growth

Neuropeptide Y (NPY), a sympathetic cotransmitter, acts via G protein-coupled receptors to stimulate constriction and vascular smooth muscle cell (VSMC) proliferation through interactions with its Y1 receptors. However, VSMC proliferation appears bimodal, with high- and low-affinity peaks differentially blocked by antagonists of both Y1 and Y5 receptors. Here, we sought to determine the signaling mechanisms of NPY-mediated bimodal mitogenesis. In rat aortic VSMCs, NPY's mitogenic effect at all concentrations was blocked by pertussis toxin and was associated with decreased forskolin-stimulated cAMP levels. NPY also increased intracellular calcium levels; in contrast to mitogenesis, this effect was dose dependent. The rise in intracellular Ca2+ depended on extracellular Ca2+ and was mediated via activation of Y1 receptors, but not Y5 receptors. Despite differences in calcium, the signaling pathways activated at low and high NPY concentrations were similar. The mitogenic effect of the peptide at all doses was completely blocked by inhibitors of calcium/calmodulin-dependent kinase II (CaMKII), protein kinase C (PKC), and mitogen-activated protein kinase kinase, MEK1/2. Thus, in VSMCs, NPY-mediated mitogenesis signals primarily via Y1 receptors activating 2 Ca2+-dependent, growth-promoting pathways -- PKC and CaMKII. At the high-affinity peak, these 2 pathways are amplified by Y5 receptor-mediated, calcium-independent inhibition of the adenylyl cyclase - protein kinase A (PKA) pathway. All 3 mechanisms converge to the extracellular signal-regulated kinases (ERK1/2) signaling cascade and lead to VSMC proliferation.

Cholinergic regulation of neuropeptide Y synthesis and release in human neuroblastoma cells

The biosynthesis and release of neuropeptide Y (NPY) is regulated by several factors. Here, the effect of the muscarinic agonist carbachol on NPY biosynthesis and release was analyzed utilizing the SH-SY5Y human neuroblastoma cell line. We observed that: (a) carbachol moderately increased the post-translational cleavage of proNPY to NPY; (b) carbachol treatment stimulated NPY accumulation into the medium in a time- and dose-related manner; (c) protein kinase C activation is involved in carbachol-mediated NPY synthesis/release (>6h). In conclusion, the present observations support the hypothesis that muscarinic receptor activation regulates the biosynthesis and secretion of NPY.

Neuropeptide y receptor selective ligands in the treatment of obesity

Obesity is a serious public health problem throughout the world, affecting both developed societies and developing countries. The central nervous system has developed a meticulously interconnected circuitry in order to keep us fed and in an adequate nutritional state. One of these consequences is that an energy-dense environment favors the development of obesity. Neuropeptide Y (NPY) is one of the most abundant and widely distributed peptides in the central nervous system of both rodents and humans and has been implicated in a variety of physiological actions. Within the hypothalamus, NPY plays an essential role in the control of food intake and body weight. Centrally administered NPY causes robust increases in food intake and body weight and, with chronic administration, can eventually produce obesity. NPY activates a population of at least six G protein-coupled Y receptors. NPY analogs exhibit varying degrees of affinity and specificity for these Y receptors. There has been renewed speculation that ligands for Y receptors may be of benefit for the treatment of obesity. This review highlights the therapeutic potential of Y(1), Y(2), Y(4), and Y(5) receptor agonists and antagonists as additional intervention to treat human obesity.

Renal and cardiac neuropeptide Y and NPY receptors in a rat model of congestive heart failure

Neuropeptide Y (NPY) is coreleased with norepinephrine and stimulates vasoconstriction, vascular and cardiomyocyte hypertrophy via Y1 receptors (R) and angiogenesis via Y2R. Although circulating NPY is elevated in heart failure, NPY's role remains unclear. Activation of the NPY system was determined in Wistar rats with the aortocaval (A-V) fistula model of high-output heart failure. Plasma NPY levels were elevated in A-V fistula animals (115.7 +/- 15.3 vs. 63.1 +/- 17.4 pM in sham, P < 0.04). Animals either compensated [urinary Na(+) excretion returning to normal with moderate disease (COMP)] or remained decompensated with severe cardiac and renal failure (urinary Na(+) excretion <0.5 meq/day), increased heart weight, decreased mean arterial pressure and renal blood flow (RBF), and death within 5-7 days (DECOMP). Cardiac and renal tissue NPY decreased with heart failure, proportionate to the severity of renal complications. Cardiac and renal Y1R mRNA expression also decreased (1.5-fold, P < 0.005) in rats with heart failure. In contrast, Y2R expression increased up to 72-fold in the heart and 5.7-fold in the kidney (P < 0.001) proportionate to severity of heart failure and cardiac hypertrophy. Changes in receptor expression were confirmed since the Y1R agonist, [Leu31, Pro34]-NPY, had no effect on RBF, whereas the Y2R agonist (13-36)-NPY increased RBF to compensate for disease. Thus, in this model of heart failure, cardiac and renal NPY Y1 receptors decrease and Y2 receptors increase, suggesting an increased effect of NPY on the receptors involved in cardiac remodeling and angiogenesis, and highlighting an important regulatory role of NPY in congestive heart failure.

Sympathectomy decreases size and invasiveness of tongue cancer in rats

The sympathetic nervous system plays a role in carcinogenesis wherein locally released sympathetic neurotransmitters affect proliferation, angiogenesis, vessel permeability, lymphocyte traffic and cytokine production. The present in vivo study was designed to investigate whether surgical sympathectomy, both unilateral and bilateral, had an effect on tumor growth, interstitial fluid pressure (IFP) and lymphatics in rat tongue cancer. We used 4-nitroquinoline-1-oxide (4-NQO) in drinking water for 19 weeks to induce tongue cancer in 20 Dark Agouti rats. After 11 weeks, one group underwent unilateral sympathectomy and another underwent bilateral sympathectomy, while the third group underwent sham surgery. By 19 weeks, tumors in the bilaterally sympathectomized (BL-SCGx) rats were significantly smaller (P<0.05), more diffuse in appearance and less invasive (P<0.05) compared with the large exophytic tumors in the sham-operated rats. The relative lymphatic area was significantly decreased (P<0.05) in tumors in the BL-SCGx rats compared with the sham group. Interestingly, the tumors in rats that underwent unilateral or bilateral sympathectomy had a significantly lower (P<0.05) IFP than those in sham rats. Lack of tyrosine hydroxylase (TH) immunoreactive nerves and few neuropeptide Y (NPY) positive fibers indicate absence of sympathetic nerve fibers in the bilateral sympathectomized group. The peritumoral lymph vessel area was correlated with the tumor size (P<0.001), depth of invasion (P<0.001), weight of rats (P<0.005) and IFP (P<0.05). In conclusion, the present study presents evidence that deprivation of sympathetic nerves decreases tumor growth in rat tongue, probably caused by decreasing IFP and lymph vessel area.

Possible roles of neuropeptide Y Y3-receptor subtype in rat aortic endothelial cell proliferation under hypoxia, and its specific signal transduction

The present study was undertaken to determine whether neuropeptide Y (NPY) induces proliferation of rat aortic endothelial cells (RAECs). Since NPY increased the permeability of RAEC monolayers to large molecules via the NPY Y3 receptor, RAEC proliferation has been evaluated in terms of NPY-receptor subtypes and also intracellular mechanisms. RAECs were incubated with gases containing 20, 15, or 10% O2 and a certain amount of N2, depending on the O2 content in 5% CO2 incubators. NPY (10−9–10−6 M) increased the RAEC numbers under hypoxic conditions, such as 15 or 10% O2. Peptide YY elicited no proliferative effect on RAEC, and NPY-(18-36) inhibited the NPY-induced increase in cell number, suggesting that NPY increases the RAEC count through the NPY Y3 receptor. Pertussis toxin, U-73122, GF-109203X, myristorylated autocamtide-2-related inhibitory peptide, and wortmannin inhibited the NPY-induced proliferation of RAEC concentration dependently. DY9760e little affected the proliferation caused by NPY. ML-9 and imatinib actually enhanced the NPY-induced proliferation of cells. These results indicated that the NPY Y3 receptor is coupled with Gi protein, and that NPY-induced increases in RAEC proliferation are mediated by phospholipase C-protein kinase C and/or phosphatidylinositol 3-kinase pathways. In intracellular Ca2+-calmodulin-dependent pathways, calmodulin-dependent protein kinase II partly participates in the NPY-induced cell proliferation. Regarding the previously reported effect of NPY on the permeability of RAEC monolayers to large molecules, it is probable that protein kinase C and phosphatidylinositol 3-kinase pathways are activated for both permeability and cell proliferation induced by NPY under hypoxia, relevant to new insights into the roles of NPY in ischemia-hypoxia.

Neuropeptide Y (NPY) and NPY receptors in the cardiovascular system: implication in the regulation of intracellular calcium

The 3-dimensional confocal microscopy technique has allowed us to identify the presence of yet another cardioactive factor and its receptor, namely neuropeptide Y (NPY) and its Y1 receptor, at the level of vascular smooth muscle cells and heart cells including endocardial endothelial cells (EECs). Using this technique, we also demonstrated that NPY is able to induce an increase in both cytosolic and nuclear calcium in all these cell types. Furthermore, besides being expressed at the level of EECs, NPY is also released from these cells following a sustained increase of intracellular Ca2+. This suggests the ability of NPY to contribute to the regulation of the excitation-secretion coupling of EECs and the excitation-contraction coupling of cardiomyocytes and vascular smooth muscle cells.

Stress, NPY and vascular remodeling: Implications for stress-related diseases

Neuropeptide Y (NPY) has long been known to be involved in stress, centrally as an anxiolytic neuromodulator, and peripherally as a sympathetic nerve- and in some species, platelet-derived vasoconstrictor. The peptide is also a vascular mitogen, via Y1/Y5, and is angiogenic via Y2/Y5 receptors. Arterial injury activates platelet NPY and vascular Y1 receptors, inducing medial hypertrophy and neointima formation. Exogenous NPY, dipeptidyl peptidase IV (DPPIV, forming an Y2/Y5-selective agonist) and chronic stress augment these effects and occlude vessels with atherosclerotic-like lesions, containing thrombus and lipid-laden macrophages. Y1 antagonist blocks stress-induced vasoconstriction and post-angioplasty occlusions, and hence may be therapeutic in angina and atherosclerosis/restenosis. Conversely, tissue ischemia activates neuronal and platelet-derived NPY, Y2/Y5 and DPPIV, which stimulate angiogenesis/arteriogenesis. NPY-Y2-DPPIV agonists may be beneficial for ischemic revascularization and wound healing, whereas antagonists may be therapeutic in retinopathy, tumors, and obesity. Since stress is an underestimated risk factor in many of these conditions, NPY-based drugs may offer new treatment possibilities.

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

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

Neuropeptide Y induces migration, proliferation, and tube formation of endothelial cells bimodally via Y1, Y2, and Y5 receptors

Previously we discovered that NPY induces ischemic angiogenesis by activating Y2 and Y5 receptors. The receptors that mediate specific steps of the complex process of angiogenesis are unknown. Here, we studied in vitro NPY receptors subtypes involved in migration, proliferation, and differentiation of human endothelial cells. In cells that expressed Y1, Y2, and Y5 receptors, NPY bimodally stimulated migration and proliferation with a 2-fold increase at 10(-12) M and 10(-8) M (high- and low-affinity peaks, respectively). Preincubation of cells with NPY up-regulated the Y5 receptor and markedly enhanced endothelial cell migration and proliferation. NPY-induced endothelial cell migration was mimicked by agonists and fully blocked by antagonists for any specific NPY receptors (Y1, Y2, or Y5), while proliferation was blocked by any two antagonists (Y1+Y2, Y1+Y5, or Y2+Y5), and capillary tube formation on Matrigel was blocked by all three (Y1+Y2+Y5). Thus, NPY-induced angiogenesis requires participation of Y1, Y2, and Y5 receptor subtypes, with the Y5 receptor acting as an enhancer. We propose that these receptors form heteromeric complexes, and the Y1/Y2/Y5 receptor oligomer may be the uncloned Y3 receptor.

Neuropeptide Y in neural crest-derived tumors: effect on growth and vascularization

Neuropeptide Y (NPY) is a sympathetic neurotransmitter recently found to be a potent growth and angiogenic factor. The peptide and its receptors are abundant in neural crest-derived tumors, such as sympathetic neuroblastomas and pheochromocytomas, as well as parasympathetic Ewing's sarcoma family of tumors. NPY regulates their growth directly, by an autocrine activation of tumor cell proliferation or apoptosis, and indirectly, by its angiogenic activity. The overall effect of the peptide on tumor growth depends on a balance between these processes and the type of receptors expressed in the tumor cells. Thus, NPY and its receptors may become targets for the treatment of neural tumors, directed against both tumor cell proliferation and angiogenesis.