Neuropeptide Y expression, localization and cellular transducing effects in HUVEC

Neuropeptide Y, a paracrine factor secreted by cancer cells, is an independent regulator of angiogenesis in colon cancer

BACKGROUND

Resistance to anti-angiogenic therapies targeting vascular endothelial growth factor-A (VEGF-A) stems from VEGF-A independent angiogenesis mediated by other proangiogenic factors. Therefore identifying these factors in colon adenocarcinoma (CA) will reveal new therapeutic targets.

METHODS

Neuropeptide Y (NPY) and Y2 receptor (Y2R) expressions in CA were studied by immunohistochemical analysis. Orthotopic HT29 with intact VEGF-A gene and VEGF-A knockdown (by CRISPR/Cas9 gene-editing technique) HT29 colon cancer-bearing mice were treated with specific Y2R antagonists, and the effects on angiogenesis and tumour growth were studied. The direct effect of NPY on angiogenesis and the underlying molecular mechanism was elucidated by the modulation of Y2R receptors expressed on colonic endothelial cells (CEC).

RESULTS

The results demonstrated that NPY and Y2R are overexpressed in human CA, orthotopic HT29, and most interestingly in VEGF-A-depleted orthotopic HT29 tumours. Treatment with Y2R antagonists inhibited angiogenesis and thereby HT29 tumour growth. Blocking /silencing Y2R abrogated NPY-induced angiogenic potential of CEC. Mechanistically, NPY regulated the activation of the ERK/MAPK signalling pathway in CEC.

CONCLUSIONS

NPY derived from cancer cells independently regulates angiogenesis in CA by acting through Y2R present on CEC. Targeting NPY/Y2R thus emerges as a novel potential therapeutic strategy in CA.

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.

Neuropeptide Y and Metabolism Syndrome: An Update on Perspectives of Clinical Therapeutic Intervention Strategies

Through the past decade of research, the pathogenic mechanisms underlying metabolic syndrome have been suggested to involve not only the peripheral tissues, but also central metabolic regulation imbalances. The hypothalamus, and the arcuate nucleus in particular, is the control center for metabolic homeostasis and energy balance. Neuropeptide Y neurons are particularly abundantly expressed in the arcuate of the hypothalamus, where the blood-brain barrier is weak, such as to critically integrate peripheral metabolic signals with the brain center. Herein, focusing on metabolic syndrome, this manuscript aims to provide an overview of the regulatory effects of Neuropeptide Y on metabolic syndrome and discuss clinical intervention strategy perspectives for neurometabolic disease.

Mechanisms of action of neuropeptide Y on stem cells and its potential applications in orthopaedic disorders

Musculoskeletal disorders are the leading causes of disability and result in reduced quality of life. The neuro-osteogenic network is one of the most promising fields in orthopaedic research. Neuropeptide Y (NPY) system has been reported to be involved in the regulations of bone metabolism and homeostasis, which also provide feedback to the central NPY system via NPY receptors. Currently, potential roles of peripheral NPY in bone metabolism remain unclear. Growing evidence suggests that NPY can regulate biological actions of bone marrow mesenchymal stem cells, hematopoietic stem cells, endothelial cells, and chondrocytes via a local autocrine or paracrine manner by different NPY receptors. The regulative activities of NPY may be achieved through the plasticity of NPY receptors, and interactions among the targeted cells as well. In general, NPY can influence proliferation, apoptosis, differentiation, migration, mobilization, and cytokine secretion of different types of cells, and play crucial roles in the development of bone delayed/non-union, osteoporosis, and osteoarthritis. Further basic research should clarify detailed mechanisms of action of NPY on stem cells, and clinical investigations are also necessary to comprehensively evaluate potential applications of NPY and its receptor-targeted drugs in management of musculoskeletal disorders.

Potential metabolic and behavioural roles of the putative endocannabinoid receptors GPR18, GPR55 and GPR119 in feeding

Endocannabinoids are ancient biomolecules involved in several cellular (e.g., metabolism) and physiological (e.g., eating behaviour) functions. Indeed, eating behaviour alterations in marijuana users have led to investigate the orexigen-ic/anorexigenic effects of cannabinoids in animal/human models. This increasing body of research suggests that the endo-cannabinoid system plays an important role in feeding control. Accordingly, within the endocannabinoid system, canna-binoid receptors, enzymes and genes represent potential therapeutic targets for dealing with multiple metabolic and behav-ioural dysfunctions (e.g., obesity, anorexia, etc.). Paradoxically, our understanding on the endocannabinoid system as a cel-lular mediator is yet limited. For example: (i) only two cannabinoid receptors have been classified, but they are not enough to explain the pharmacological profile of several experimental effects induced by cannabinoids; and (ii) several orphan G pro-tein-coupled receptors (GPCRs) interact with cannabinoids and we do not know how to classify them (e.g., GPR18, GPR55 and GPR119; amongst others).

On this basis, the present review attempts to summarize the lines of evidence supporting the potential role of GPR18, GPR55 and GPR119 in metabolism and feeding control that may explain some of the divergent effects and puzzling data re-lated to cannabinoid research. Moreover, their therapeutic potential in feeding behaviour alterations will be considered.

Platelet Lysate-Derived Neuropeptide y Influences Migration and Angiogenesis of Human Adipose Tissue-Derived Stromal Cells

Neuropeptide Y (NPY), a powerful neurotransmitter of the central nervous system, is a key regulator of angiogenesis and biology of adipose depots. Intriguingly, its peripheral vascular and angiogenic powerful activity is strictly associated to platelets, which are source of clinical hemoderivates, such as platelet lysate (PL), routinely employed in several clinical applications as wound healing, and to preserve ex vivo the progenitor properties of the adipose stromal cells pool. So far, the presence of NPY in PL and its biological effects on the adipose stromal cell fraction (ASCs) have never been investigated. Here, we aimed to identify endogenous sources of NPY such as PL-based preparations and to investigate which biological properties PL-derived NPY is able to exert on ASCs. The results show that PL contains a high amount of NPY, which is in part also excreted by ASCs when stimulated with PL. The protein levels of the three main NPY subtype receptors (Y1, Y2, Y5) are unaltered by stimulation of ASCs with PL, but their inhibition through selective pharmacological antagonists, considerably enhances migration, and a parallel reduction of angiogenic features of ASCs including decrease in VEGF mRNA and intracellular calcium levels, both downstream targets of NPY. The expression of VEGF and NPY is enhanced within the sites of neovascularisation of difficult wounds in patients after treatment with leuco-platelet concentrates. Our data highlight the presence of NPY in PL preparations and its peripheral effects on adipose progenitors.

Bone Injury and Repair Trigger Central and Peripheral NPY Neuronal Pathways

Bone repair is a specialized type of wound repair controlled by complex multi-factorial events. The nervous system is recognized as one of the key regulators of bone mass, thereby suggesting a role for neuronal pathways in bone homeostasis. However, in the context of bone injury and repair, little is known on the interplay between the nervous system and bone. Here, we addressed the neuropeptide Y (NPY) neuronal arm during the initial stages of bone repair encompassing the inflammatory response and ossification phases in femoral-defect mouse model. Spatial and temporal analysis of transcriptional and protein levels of NPY and its receptors, Y1R and Y2R, reported to be involved in bone homeostasis, was performed in bone, dorsal root ganglia (DRG) and hypothalamus after femoral injury. The results showed that NPY system activity is increased in a time- and space-dependent manner during bone repair. Y1R expression was trigged in both bone and DRG throughout the inflammatory phase, while a Y2R response was restricted to the hypothalamus and at a later stage, during the ossification step. Our results provide new insights into the involvement of NPY neuronal pathways in bone repair.

Cellular targets for neuropeptide Y-mediated control of adult neurogenesis

Neuropeptides are emerging as key regulators of stem cell niche activities in health and disease, both inside and outside the central nervous system (CNS). Among them, neuropeptide Y (NPY), one of the most abundant neuropeptides both in the nervous system and in non-neural districts, has become the focus of much attention for its involvement in a wide range of physiological and pathological conditions, including the modulation of different stem cell activities. In particular, a pro-neurogenic role of NPY has been evidenced in the neurogenic niche, where a direct effect on neural progenitors has been demonstrated, while different cellular types, including astrocytes, microglia and endothelial cells, also appear to be responsive to the peptide. The marked modulation of the NPY system during several pathological conditions that affect neurogenesis, including stress, seizures and neurodegeneration, further highlights the relevance of this peptide in the regulation of adult neurogenesis. In view of the considerable interest in understanding the mechanisms controlling neural cell fate, this review aims to summarize and discuss current data on NPY signaling in the different cellular components of the neurogenic niche in order to elucidate the complexity of the mechanisms underlying the modulatory properties of this peptide.

Transcriptional regulatory mechanisms underlying the GABAergic neuron fate in different diencephalic prosomeres

Diverse mechanisms regulate development of GABAergic neurons in different regions of the central nervous system. We have addressed the roles of a proneural gene, Ascl1, and a postmitotic selector gene, Gata2, in the differentiation of GABAergic neuron subpopulations in three diencephalic prosomeres: prethalamus (P3), thalamus (P2) and pretectum (P1). Although the different proliferative progenitor populations of GABAergic neurons commonly express Ascl1, they have distinct requirements for it in promotion of cell-cycle exit and GABAergic neuron identity. Subsequently, Gata2 is activated as postmitotic GABAergic precursors are born. In P1, Gata2 regulates the neurotransmitter identity by promoting GABAergic and inhibiting glutamatergic neuron differentiation. Interestingly, Gata2 defines instead the subtype of GABAergic neurons in the rostral thalamus (pTh-R), which is a subpopulation of P2. Without Gata2, the GABAergic precursors born in the pTh-R fail to activate subtype-specific markers, but start to express genes typical of GABAergic precursors in the neighbouring P3 domain. Thus, our results demonstrate diverse mechanisms regulating differentiation of GABAergic neuron subpopulations and suggest a role for Gata2 as a selector gene of both GABAergic neuron neurotransmitter and prosomere subtype identities in the developing diencephalon. Our results demonstrate for the first time that neuronal identities between distinct prosomeres can still be transformed in postmitotic neuronal precursors.

The interplay between the Rab27A effectors Slp4-a and MyRIP controls hormone-evoked Weibel-Palade body exocytosis

Weibel-Palade body (WPB) exocytosis underlies hormone-evoked VWF secretion from endothelial cells (ECs). We identify new endogenous components of the WPB: Rab3B, Rab3D, and the Rab27A/Rab3 effector Slp4-a (granuphilin), and determine their role in WPB exocytosis. We show that Rab3B, Rab3D, and Rab27A contribute to Slp4-a localization to WPBs. siRNA knockdown of Slp4-a, MyRIP, Rab3B, Rab3D, Rab27A, or Rab3B/Rab27A, or overexpression of EGFP-Slp4-a or EGFP-MyRIP showed that Slp4-a is a positive and MyRIP a negative regulator of WPB exocytosis and that Rab27A alone mediates these effects. We found that ECs maintain a constant amount of cellular Rab27A irrespective of the WPB pool size and that Rab27A (and Rab3s) cycle between WPBs and a cytosolic pool. The dynamic redistribution of Rab proteins markedly decreased the Rab27A concentration on individual WPBs with increasing WPB number per cell. Despite this, the probability of WPB release was independent of WPB pool size showing that WPB exocytosis is not determined simply by the absolute amount of Rab27A and its effectors on WPBs. Instead, we propose that the probability of release is determined by the fractional occupancy of WPB-Rab27A by Slp4-a and MyRIP, with the balance favoring exocytosis.

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.

The role of non-synonymous NPY gene polymorphism in the nitric oxide production in HUVECs

A Leu7Pro change in the signal peptide of preproNPY is a functional substitution, which changes the processing of NPY in cells and associates with several cardiovascular and metabolic conditions in humans. The current study investigates the effect of the P7 allele in endothelial cells, where decreased nitric oxide (NO) production is a promoting factor to endothelial dysfunction. The function of NO system was assessed in the human umbilical vein endothelial cells (HUVECs) with [p.L7]+[p.L7] or [p.L7]+[p.P7] genotype. NPY seems to have a significant influence on NO system in HUVECs, and the responses are time and genotype dependent. HUVECs with [p.L7]+[p.P7] genotype seem to have higher basal production of NO, but after a long term treatment with NPY these cells express less eNOS mRNA and overall eNOS protein levels are lower. These significant differences in the NO bioavailability may explain the association of the L7P polymorphism with several cardiovascular complications.

The intracellular mobility of NPY and a putative mitochondrial form of NPY in neuronal cells

Preproneuropeptide Y is a precursor peptide to mature neuropeptide Y (NPY), which is a universally expressed peptide in the central and peripheral nervous system. NPY is normally routed to endoplasmic reticulum and secretory vesicles in cells, which secrete NPY. In our previous studies, we found a functional Leucine7 to Proline7 (L7P) polymorphism in the signal peptide sequence of preproNPY. This polymorphism affects the secretion of NPY and causes multiple physiological effects in humans. The sequence of NPY mRNA contains two in frame kozak sequences that allow translation initiation to shift, and translation of two proteins. In addition to mature NPY(1-36) also a putative truncated NPY(17-36) with mitochondrial targeting signal is produced. The purpose of this study was to investigate the protein mobility of the putative mitochondrial fragment and the effect of the L7P polymorphism on the cellular level using GFP tagged constructs. The mobility was studied with fluorescence recovery after photobleaching technique in a neuronal cell line. We found that the mobility of the secretory vesicles with NPY(1-36) in cells with L7P genotype was increased in comparison to vesicle mobility in cells with the more abundant L7L genotype. The mobility in the cells with the putative mitochondrial construct was found to be very low. According to the results of the present study, the mitochondrial truncated peptide stays in the mitochondrion. It can be hypothesized that this could be one of the factors affecting energy balance of the membranes of the mitochondrion.

NPY in rat retina is present in neurons, in endothelial cells and also in microglial and Müller cells

NPY is present in the retina of different species but its role is not elucidated yet. In this work, using different rat retina in vitro models (whole retina, retinal cells in culture, microglial cell cultures, rat Müller cell line and retina endothelial cell line), we demonstrated that NPY staining is present in the retina in different cell types: neurons, macroglial, microglial and endothelial cells. Retinal cells in culture express NPY Y(1), Y(2), Y(4) and Y(5) receptors. Retina endothelial cells express all NPY receptors except NPY Y(5) receptor. Moreover, NPY is released from retinal cells in culture upon depolarization. In this study we showed for the first time that NPY is present in rat retina microglial cells and also in rat Müller cells. These in vitro models may open new perspectives to study the physiology and the potential pathophysiological role of NPY in the retina.

Intracellular targeting of truncated secretory peptides in the mammalian heart and brain

Secretory polypeptides are vital for nervous system function, sleep, reproduction, growth, and metabolism. Ribosomes scanning the 5'-end of mRNA usually detect the first AUG site for initiating translation. The nascent propeptide chain is then directed via a signal-peptide into the endoplasmic reticulum, processed through the Golgi stacks, and packaged into secretory vesicles. By expressing prepropeptide-EGFP fusion proteins, we observed unusual destinations, mitochondria, nucleus, and cytoplasm, of neuropeptide Y (NPY), atrial natriuretic peptide, and growth hormone in living murine cardiac cells and hypothalamic slices. Subcellular expression was modulated by Zn++ or mutations of N-terminal prohormone sequences but was not due to overexpression in the trans-Golgi network. Mitochondrial targeting of NPY also occurred without the EGFP tag, was enhanced by site-directed mutagenesis of the first AUG initiation site, and abolished by mutation of the second AUG. Immunological methods indicated the presence of N-terminal truncated NPY in mitochondria. Imaging studies showed depolarization of NPY-containing mitochondria. P-SORT software correctly predicted the secondary intracellular destinations and suggested such destinations for many neuropeptides and peptide hormones known. Thus, mammalian cells may retarget secretory peptides from extracellular to intracellular sites by skipping the first translation-initiation codon and thereby alter mitochondrial function, gene expression, and secretion.

Mitochondrial targeting signal in human neuropeptide Y gene

Neuropeptide Y (NPY) is universally expressed in many different neuronal and non-neuronal cells. Human NPY gene has two in-frame kozak sequences and thus, has potentially two translation initiation sites producing two NPY peptides with different molecular weights. In the present study, the intracellular location of NPY was studied in endothelial cells endogenously expressing NPY, and in neuronal (SK-N-BE) and non-neuronal (CHO-K1) cells transfected with NPY-GFP-constructs. By mutating kozak sequences we discovered that kozak-1 directs the NPY peptide to secretory vesicles, and kozak-2 is a prerequisite for mitochondrial targeting. If both kozak sequences are present, non-neuronal cells seem to benefit leaky scanning to initiate translation at both initiation sites, in contrast to neuronal cells, which prefer the kozak-1. This finding suggests that both the kozak sequences of NPY mRNA can be used in the translation depending on the cell type. The size and the function of the novel NPY fragment routed to mitochondria remains to be determined.