Neuropeptide B and W: neurotransmitters in an emerging G-protein-coupled receptor system

The prevalence of copy number increase at multiallelic copy number variants associated with cave colonization

Copy number variation is a common contributor to phenotypic diversity, yet its involvement in ecological adaptation is not easily discerned. Instances of parallelly evolving populations of the same species in a similar environment marked by strong selective pressures present opportunities to study the role of copy number variants (CNVs) in adaptation. By identifying CNVs that repeatedly occur in multiple populations of the derived ecotype and are not (or are rarely) present in the populations of the ancestral ecotype, the association of such CNVs with adaptation to the novel environment can be inferred. We used this paradigm to identify CNVs associated with recurrent adaptation of the Mexican tetra (Astyanax mexicanus) to cave environment. Using a read-depth approach, we detected CNVs from previously re-sequenced genomes of 44 individuals belonging to two ancestral surfaces and three derived cave populations. We identified 102 genes and 292 genomic regions that repeatedly diverge in copy number between the two ecotypes and occupy 0.8% of the reference genome. Functional analysis revealed their association with processes previously recognized to be relevant for adaptation, such as vision, immunity, oxygen consumption, metabolism, and neural function and we propose that these variants have been selected for in the cave or surface waters. The majority of the ecotype-divergent CNVs are multiallelic and display copy number increases in cavefish compared to surface fish. Our findings suggest that multiallelic CNVs - including gene duplications - and divergence in copy number provide a fast route to produce novel phenotypes associated with adaptation to subterranean life.

Involvement of the kisspeptin system in regulation of sexual behaviors in medaka

In mammals, kisspeptin (Kiss1) neurons are generally considered as a sex steroid-dependent key regulator of hypothalamic-pituitary-gonadal (HPG) axis. In contrast, previous studies in non-mammalian species, especially in teleosts, propose that Kiss1 is not directly involved in the HPG axis regulation, which suggests some sex-steroid-dependent functions of kisspeptin(s) other than the HPG axis regulation in non-mammals. Here, we used knockout (KO) medaka of kisspeptin receptor-coding genes (gpr54-1 and gpr54-2) and examined possible roles of kisspeptin in the regulation of sexual behaviors. We found that the KO pairs of gpr54-1, but not gpr54-2, spawned fewer eggs and exhibited delayed spawning than wild type pairs. Detailed behavior analysis suggested that the KO females are responsible for the delayed spawning and that the KO males showed hyper-motivation for courtship. Taken together, the present finding suggests that one of the reproductive-state-dependent functions of the Kiss1 may be the control of successful sexual behaviors.

Neuropeptide B (NPB) and NPB receptor 2b (NPBWR2b) in the ricefield eel Monopterus albus: expression and potential involvement in the regulation of gonadotropins

The neuropeptide B/W signaling system is composed of neuropeptide B (NPB), neuropeptide W (NPW), and two cognate receptors, NPBWR1 and NPBWR2, which are involved in diverse physiological processes, including the central regulation of neuroendocrine axes in vertebrates. The components of this signaling system are not well conserved during vertebrate evolution, implicating its functional diversity. The present study characterized the ricefield eel neuropeptide B/W system, generated a specific antiserum against the neuropeptide B/W receptor, and examined the potential roles of the system in the regulation of adenohypophysial functions. The ricefield eel genome contains npba, npbb, and npbwr2b but lacks the npw, npbwr1, and npbwr2a genes. The loss of npw and npbwr1 probably occurred at the base of ray-finned fish radiation and that of npbwr2a species specifically in ray-finned fish. Npba and npbb genes are produced through whole-genome duplication (WGD) in ray-finned fish. The ricefield eel npba was expressed in the brain and some peripheral tissues, while npbb was predominantly expressed in the brain. The ricefield eel npbwr2b was also expressed in the brain and in some peripheral tissues, such as the pituitary, gonad, heart, and eye. Immunoreactive Npbwr2b was shown to be localized to Lh and Fsh cells but not to Gh or Prl cells in the pituitary of ricefield eels. Npba upregulated the expression of fshb and cga but not lhb mRNA in pituitary fragments of ricefield eels cultured in vitro. The results of the present study suggest that the NPB system of ricefield eels may be involved in the neuroendocrine regulation of reproduction.

Evidence for Neuropeptide W Acting as a Physiological Corticotropin-releasing Inhibitory Factor in Male Chickens

In vertebrates, adrenocorticotropin (ACTH), released by the pituitary gland, is a critical part of the stress axis and stress response. Generally, the biosynthesis and secretion of ACTH are controlled by both hypothalamic stimulatory factors and inhibitory factors [eg, ACTH-releasing inhibitory factor (CRIF)], but the identity of this CRIF remains unrevealed. We characterized the neuropeptide B (NPB)/neuropeptide W (NPW) system in chickens and found that NPW could directly target the pituitary to inhibit growth hormone (GH) and prolactin (PRL) secretion via neuropeptide B/W receptor 2 (NPBWR2), which is completely different from the mechanism in mammals. The present study first carried out a series of assays to investigate the possibility that NPW acts as a physiological CRIF in chickens. The results showed that (1) NPW could inhibit ACTH synthesis and secretion by inhibiting the 3',5'-cyclic adenosine 5'-monophosphate/protein kinase A signaling cascade in vitro and in vivo; (2) NPBWR2 was expressed abundantly in corticotrophs (ACTH-producing cells), which are located mainly in cephalic lobe of chicken pituitary, as demonstrated by single-cell RNA-sequencing, immunofluorescent staining, and fluorescence in situ hybridization; (3) dexamethasone could stimulate pituitary NPBWR2 and hypothalamic NPW expression in chicks, which was accompanied by the decease of POMC messenger RNA levels, as revealed by in vitro and subcutaneous injection assays; and (4) the temporal expression profiles of NPW-NPBWR2 pair in hypothalamus-pituitary axis and POMC in pituitary were almost unanimous in chicken. Collectively, these findings provide comprehensive evidence for the first time that NPW is a potent physiological CRIF in chickens that plays a core role in suppressing the activity of the stress axis.

Neuropeptide B/W receptor 1 peptidomimetic agonists: Structure-activity relationships and plasma stability

Neuropeptides B and W (NPB and NPW) are endogenous ligands of the Neuropeptide B/W Receptor 1 (NPBWR1) which has been implicated in a wide range of functions including regulation of pain and energy homeostasis. There is currently little information on the structure-activity relationships (SAR) of these two neuropeptides. In a quest to develop stable and potent NPBWR1 peptidomimetic agonists, we performed systematic SAR by truncation, Alanine/Glycine and d-amino acid scans, and replacement with unnatural amino acids. Evaluation in the NPBWR1 calcium assay revealed that the C-terminal GRAAGLL and N-terminal WYK regions constitute the two-epitope pharmacophore for NPBWR1 agonism. Replacement of the N-terminal Trp with its desaminoTrp residue resulted in compound 30 which exhibited nanomolar potency comparable to the endogenous NPB at NPBWR1 (Calcium assay: EC₅₀ = 8 nM vs. 13 nM, cAMP assay: 2.7 nM vs 3.5 nM) and enhanced metabolic stability against rat plasma (39.1 min vs. 11.9 min).

Biodata Mining of Differentially Expressed Genes between Acute Myocardial Infarction and Unstable Angina Based on Integrated Bioinformatics

Acute coronary syndrome (ACS) is a complex syndrome of clinical symptoms. In order to accurately diagnose the type of disease in ACS patients, this study is aimed at exploring the differentially expressed genes (DEGs) and biological pathways between acute myocardial infarction (AMI) and unstable angina (UA). The GSE29111 and GSE60993 datasets containing microarray data from AMI and UA patients were downloaded from the Gene Expression Omnibus (GEO) database. DEG analysis of these 2 datasets is performed using the “limma” package in R software. DEGs were also analyzed using protein-protein interaction (PPI), Molecular Complex Detection (MCODE) algorithm, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Correlation analysis and “cytoHubba” were used to analyze the hub genes. A total of 286 DEGs were obtained from GSE29111 and GSE60993, including 132 upregulated genes and 154 downregulated genes. Subsequent comprehensive analysis identified 20 key genes that may be related to the occurrence and development of AMI and UA and were involved in the inflammatory response, interaction of neuroactive ligand-receptor, calcium signaling pathway, inflammatory mediator regulation of TRP channels, viral protein interaction with cytokine and cytokine receptor, human cytomegalovirus infection, and cytokine-cytokine receptor interaction pathway. The integrated bioinformatical analysis could improve our understanding of DEGs between AMI and UA. The results of this study might provide a new perspective and reference for the early diagnosis and treatment of ACS.

High-Fat Diet Alters the Retinal Transcriptome in the Absence of Gut Microbiota

The relationship between retinal disease, diet, and the gut microbiome has shown increasing importance over recent years. In particular, high-fat diets (HFDs) are associated with development and progression of several retinal diseases, including age-related macular degeneration (AMD) and diabetic retinopathy. However, the complex, overlapping interactions between diet, gut microbiome, and retinal homeostasis are poorly understood. Using high-throughput RNA-sequencing (RNA-seq) of whole retinas, we compare the retinal transcriptome from germ-free (GF) mice on a regular diet (ND) and HFD to investigate transcriptomic changes without influence of gut microbiome. After correction of raw data, 53 differentially expressed genes (DEGs) were identified, of which 19 were upregulated and 34 were downregulated in GF-HFD mice. Key genes involved in retinal inflammation, angiogenesis, and RPE function were identified. Enrichment analysis revealed that the top 3 biological processes affected were regulation of blood vessel diameter, inflammatory response, and negative regulation of endopeptidase. Molecular functions altered include endopeptidase inhibitor activity, protease binding, and cysteine-type endopeptidase inhibitor activity. Human and mouse pathway analysis revealed that the complement and coagulation cascades are significantly affected by HFD. This study demonstrates novel data that diet can directly modulate the retinal transcriptome independently of the gut microbiome.

The Role of Peptide Hormones Discovered in the 21st Century in the Regulation of Adipose Tissue Functions

Peptide hormones play a prominent role in controlling energy homeostasis and metabolism. They have been implicated in controlling appetite, the function of the gastrointestinal and cardiovascular systems, energy expenditure, and reproduction. Furthermore, there is growing evidence indicating that peptide hormones and their receptors contribute to energy homeostasis regulation by interacting with white and brown adipose tissue. In this article, we review and discuss the literature addressing the role of selected peptide hormones discovered in the 21st century (adropin, apelin, elabela, irisin, kisspeptin, MOTS-c, phoenixin, spexin, and neuropeptides B and W) in controlling white and brown adipogenesis. Furthermore, we elaborate how these hormones control adipose tissue functions in vitro and in vivo.

Neuropeptide W, an endogenous NPBW1 and NPBW2 ligand, produced an analgesic effect via activation of the descending pain modulatory system during a rat formalin test

Neuropeptide W (NPW) messenger ribonucleic acid (mRNA) and NPBW1 and/or NPBW2 mRNA are expressed in the descending pain inhibitory system. In the present study, we examined whether NPW microinjected into the descending pain inhibitory system, such as the periaqueductal gray (PAG), locus coeruleus (LC), and rostral ventromedial medulla (RVM), produces an analgesic effect using a rat formalin test. Microinjections of NPW into the PAG ipsilateral and contralateral to the formalin-injected side, LC ipsilateral and contralateral to the formalin-injected side, and RVM produced an analgesic effect. In the RVM study, the analgesic effect was antagonized by WAY100135, a 5-HT1A antagonist, and enhanced by prazosin, an α1 antagonist, and SB269970, a 5-HT7 antagonist. Naloxone, an opioid antagonist, also antagonized the effect of NPW in the RVM study. In the ipsilateral LC study, the analgesic effect was antagonized by WAY100135, idazoxan, an α2 antagonist, and naloxone and was enhanced by prazosin and SB269970. In the contralateral LC study, the analgesic effect was antagonized by prazosin, idazoxan, SB269970, and naloxone. The analgesic effect was antagonized by WAY100135, SB269970, idazoxan, and naloxone in the ipsilateral and contralateral PAG studies. These findings strongly suggest that NPBW1/W2 activation by NPW microinjection into the RVM, LC, and PAG affect the descending pain modulatory system and produce anti-nociceptive and pro-nociceptive effects in the rat formalin test.

Changes of protein levels in human urine reflect the dysregulation of signaling pathways of chronic kidney disease and its complications

The increasing prevalence of chronic kidney disease (CKD) seriously is threatening human health and overall quality of life. The discovery of biomarkers of pathogenesis of CKD and the associated complications are very important for CDK diagnosis and treatment. In this paper, urine protein biomarkers were investigated because urine sample collection is convenient and non-invasive. We analyzed the protein concentrations in the urine of CKD patients and extracted abnormal protein signals comparing with the healthy control groups. The enriched signaling pathways that may characterize CKD pathology were identified from these proteins. We applied surface-enhanced laser desorption and ionization time of flight mass spectrometry technology to detect different protein peaks in urine samples from patients with CKD and healthy controls. We searched the proteins corresponding to protein peaks through the UniProt database and identified the signaling pathways of CKD and its complications by using the NIH DAVID database. 42 low abundance proteins and 46 high abundance proteins in the urine samples from CKD patients were found by comparing with healthy controls. Seven KEGG pathways related to CKD and its complications were identified from the regulated proteins. These pathways included chemokine signaling pathway, cytokine-cytokine receptor interaction, oxidative phosphorylation, cardiac muscle contraction, Alzheimer's disease, Parkinson's disease, and salivary secretion. In CKD stages 2, 3, 4, and 5, five proteins showed significantly differential abundances. The differential protein signals and regulated signaling pathways will provide new insight for the pathogenesis of CKD and its complications. These altered proteins may also be used as novel biomarkers for the noninvasive and convenient diagnosis methods of CKD and its complications through urine testing in the future.

The role of orphan G protein-coupled receptors in the modulation of pain: A review

G protein-coupled receptors (GPCRs) comprise a large number of receptors. Orphan GPCRs are divided into six families. These groups contain orphan receptors for which the endogenous ligands are unclear. They have various physiological effects in the body and have the potential to be used in the treatment of different diseases. Considering their important role in the central and peripheral nervous system, their role in the treatment of pain has been the subject of some recent studies. At present, there are effective therapeutics for the treatment of pain including opioid medications and non-steroidal anti-inflammatory drugs. However, the side effects of these drugs and the risks of tolerance and dependence remain a major problem. In addition, neuropathic pain is a condition that does not respond to currently available analgesic medications well. In the present review article, we aimed to review the most recent findings regarding the role of orphan GPCRs in the treatment of pain. Accordingly, based on the preclinical findings, the role of GPR3, GPR7, GPR8, GPR18, GPR30, GPR35, GPR40, GPR55, GPR74, and GPR147 in the treatment of pain was discussed. The present study highlights the role of orphan GPCRs in the modulation of pain and implies that these receptors are potential new targets for finding better and more efficient therapeutics for the management of pain particularly neuropathic pain.

Distribution and Function of Neuropeptides W/B Signaling System

Neuropeptide W (NPW) and neuropeptide B (NPB) are two structurally and functionally related regulatory peptides, which are highly expressed in several brain regions and, additionally, in some peripheral tissues. Nevertheless, their distributions in the tissues are not similar. They act on target tissues via two subtypes of G protein-coupled receptors which are designated as NPBWR1 (GPR7) and NPBWR2 (GPR8), respectively, and possess different binding affinities. NPB activates NPBWR1, whereas NPW stimulates both the receptors with similar potency. Both of these peptides takes a part in the central regulation of neuroendocrine axes, feeding behavior, energy homeostasis, cardiovascular functions, circadian rhythm, pain sensation, modulation of inflammatory pain, and emotions. Over the past few years, studies have shown that NPB is also involved in sleep regulation. On the contrary, NPW participates in regulation of vascular myogenic tone, inhibits gastric tension sensitive vagal afferents and insulin secretion. Also, expression of NPW in the stomach is regulated by feeding. Abovementioned findings clearly demonstrate the functional diversity among NPW versus NPB signaling systems. In this review, signal transduction pathways of NPW/NPB are critically evaluated and observed together with mapping of expression of their signaling systems.

The role of neuropeptide W in energy homeostasis

Neuropeptide W is the endogenous ligand for G-protein-coupled receptors GPR7 and GPR8. In this review, we summarize findings on the distribution of neuropeptide W and its receptors in the central nervous system and the periphery, and discuss the role of NPW in food intake and energy homeostasis.

Evolutionally Conserved Function of Kisspeptin Neuronal System Is Nonreproductive Regulation as Revealed by Nonmammalian Study

The kisspeptin neuronal system, which consists of a neuropeptide kisspeptin and its receptor Gpr54, is considered in mammals a key factor of reproductive regulation, the so-called hypothalamic-pituitary-gonadal (HPG) axis. However, in nonmammalian vertebrates, especially in teleosts, existence of kisspeptin regulation on the HPG axis is still controversial. In this study, we applied multidisciplinary techniques to a teleost fish, medaka, and examined possible kisspeptin regulation on the HPG axis. First, we generated knockout medaka for kisspeptin-related genes and found that they show normal fertility, gonadal maturation, and expression of gonadotropins. Moreover, the firing activity of GnRH1 neurons recorded by the patch clamp technique was not altered by kisspeptin application. Furthermore, in goldfish, in vivo kisspeptin administration did not show any positive effect on HPG axis regulation. However, as kisspeptin genes are completely conserved among vertebrates except birds, we surmised that kisspeptin should have some important nonreproductive functions in vertebrates. Therefore, to discover novel functions of kisspeptin, we generated a gpr54-1:enhanced green fluorescent protein (EGFP) transgenic medaka, whose gpr54-1-expressing cells are specifically labeled by EGFP. Analysis of neuronal projection of gpr54-1:EGFP-expressing neurons showed that these neurons in the ventrolateral preoptic area project to the pituitary and are probably involved in endocrine regulation other than gonadotropin release. Furthermore, combination of deep sequencing, histological, and electrophysiological analyses revealed various novel neural systems that are under control of kisspeptin neurons-that is, those expressing neuropeptide Yb, cholecystokinin, isotocin, vasotocin, and neuropeptide B. Thus, our new strategy to genetically label receptor-expressing neurons gives insights into various kisspeptin-dependent neuronal systems that may be conserved in vertebrates.

Neuropeptide W modulation of gastric vagal afferent mechanosensitivity: Impact of age and sex

AIM

Gastric vagal afferents are activated in response to mechanical stimulation, an effect attenuated by neuropeptide W (NPW) in 20-week-old female mice. In this study we aimed to determine whether there were age and sex dependent effects of NPW on gastric vagal afferent mechanosensitivity.

METHODS

An in vitro gastro-oesophageal preparation was used to determine the effect of NPW on gastric vagal afferent mechanosensitivity from 8 and 20-week-old male and female C57BL/6 mice. Retrograde tracing and laser capture microdissection were used to selectively collect gastric vagal afferent cell bodies. Expression of NPW in the gastric mucosa and its receptor, GPR7, in gastric vagal afferent cell bodies was determined using quantitative RT-PCR.

RESULTS

NPW inhibited gastric tension sensitive vagal afferents from 20-week-old male and female mice, but not 8-week-old mice. In contrast, NPW inhibited the mechanosensitivity of gastric mucosal vagal afferents in 8-week-old male and female mice, but not 20-week-old mice. NPW mRNA expression in the gastric mucosa was higher in 20-week-old male mice compared to 8-week-old male mice. GPR7 mRNA expression in vagal afferent neurons innervating the gastric muscular layers was higher in 20-week-old mice compared to 8-week-old mice in both sexes.

CONCLUSION

The inhibitory effect of NPW on gastric tension sensitive and mucosal vagal afferents is age but not sex-dependent. These findings suggest that the physiological role of NPW varies depending on the age of the mice.

Compromise of endogenous neuropeptide W production abrogates the dipsogenic and pressor effects of angiotensin II in adult male rats

Neuropeptide W (NPW), an endogenous ligand for the G-protein coupled receptor GPR7, is produced in neurones in the rat hypothalamus and brain stem known to be important in the control of food intake and the neuroendocrine response to stress. In previous studies, central administration of NPW during the light phase increased food and water intake and elevated prolactin and corticosterone levels in conscious, unrestrained male rats. In the present study, central administration of small-interfering RNA (siRNA) reduced NPW levels in the hypothalamus and resulted in a failure of angiotensin II to stimulate water drinking or increase mean arterial pressure. In addition, siRNA-treated animals failed to mount a significant prolactin response to immobilisation stress, at the same time as maintaining a normal corticosterone response. These results suggest that endogenous NPW may be a physiologically relevant, downstream mediator of the central actions of angiotensin II to stimulate thirst and increase arterial pressure. In addition, NPW-producing neurones appear to participate in the hypothalamic mechanisms controlling prolactin (but not corticosterone) secretion.

International Union of Basic and Clinical Pharmacology. LXXXVIII. G protein-coupled receptor list: recommendations for new pairings with cognate ligands

In 2005, the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR) published a catalog of all of the human gene sequences known or predicted to encode G protein-coupled receptors (GPCRs), excluding sensory receptors. This review updates the list of orphan GPCRs and describes the criteria used by NC-IUPHAR to recommend the pairing of an orphan receptor with its cognate ligand(s). The following recommendations are made for new receptor names based on 11 pairings for class A GPCRs: hydroxycarboxylic acid receptors [HCA₁ (GPR81) with lactate, HCA₂ (GPR109A) with 3-hydroxybutyric acid, HCA₃ (GPR109B) with 3-hydroxyoctanoic acid]; lysophosphatidic acid receptors [LPA₄ (GPR23), LPA₅ (GPR92), LPA₆ (P2Y5)]; free fatty acid receptors [FFA4 (GPR120) with omega-3 fatty acids]; chemerin receptor (CMKLR1; ChemR23) with chemerin; CXCR7 (CMKOR1) with chemokines CXCL12 (SDF-1) and CXCL11 (ITAC); succinate receptor (SUCNR1) with succinate; and oxoglutarate receptor [OXGR1 with 2-oxoglutarate]. Pairings are highlighted for an additional 30 receptors in class A where further input is needed from the scientific community to validate these findings. Fifty-seven human class A receptors (excluding pseudogenes) are still considered orphans; information has been provided where there is a significant phenotype in genetically modified animals. In class B, six pairings have been reported by a single publication, with 28 (excluding pseudogenes) still classified as orphans. Seven orphan receptors remain in class C, with one pairing described by a single paper. The objective is to stimulate research into confirming pairings of orphan receptors where there is currently limited information and to identify cognate ligands for the remaining GPCRs. Further information can be found on the IUPHAR Database website (http://www.iuphar-db.org).

Cellular localization of receptors using antibodies visualized by light and dual labeling confocal microscopy

Immunocytochemistry can be used to visualize the binding of specific site-directed antisera to receptors in tissue sections and permits the precise identification of cell types expressing a particular receptor when viewed using a conventional light microscope or by confocal microscopy. Protocols are also described for the dual labeling of cells in the same section using primary antisera raised in two different species (one to the receptor of interest, the second to an immunogen such as a cell-specific marker or the endogenous ligand) with the corresponding secondary antisera conjugated to different fluorescent dyes.The technique has a range of applications. Subtypes of receptors can be identified and distinguished prior to the development of selective agonists or antagonists, which is particularly important for mapping orphan receptors, where the identity of the endogenous ligand in not yet known. The deletion of genes encoding receptors, particularly in mice, has emerged as a powerful tool in understanding the role of a specific receptor in physiological processes. Receptor immunocytochemistry can be used to analyze the resulting phenotype in whole body sections of mice without preselection of the tissue to be studied.

Radioligand binding assays and their analysis

Radioligand binding is widely used to characterize receptors and determine their anatomical distribution, particularly the superfamily of seven transmembrane-spanning G protein-coupled receptors for both established transmitters such as endothelin-1 and an increasing number of orphan receptors recently paired with their cognate ligands. Three types of assay are described. In saturation experiments, tissue sections, cultured cells, or homogenates are incubated with an increasing concentration of a radiolabeled ligand, which can be a labeled analog of a naturally occurring transmitter, hormone, or synthetic drug. Analysis using iterative nonlinear curve-fitting programs, such as KELL, measures the affinity of the labeled ligand for a receptor (equilibrium dissociation constant, K ( D )), receptor density (B (max)), and Hill slope (nH). The affinity and selectivity of an unlabeled ligand to compete for the binding of a fixed concentration of a radiolabeled ligand to a receptor are determined using a competition binding assay. Kinetic assays measure the rate of association to or dissociation from a receptor from which a kinetic K ( D ) may be derived. Quantitative autoradiography and image analysis is a sensitive technique to detect low levels of radiolabeled ligands and determine the anatomical distribution of receptors in sections that retain the morphology of the tissue. The measurement of bound radioligand within discrete regions of autoradiographical images using -computer-assisted image analysis is described.

Analgesic neuropeptide W suppresses seizures in the brain revealed by rational repositioning and peptide engineering

Anticonvulsant neuropeptides play an important role in controlling neuronal excitability that leads to pain or seizures. Based on overlapping inhibitory mechanisms, many anticonvulsant compounds have been found to exhibit both analgesic and antiepileptic activities. An analgesic neuropeptide W (NPW) targets recently deorphanized G-protein coupled receptors. Here, we tested the hypothesis that the analgesic activity of NPW may lead to the discovery of its antiepileptic properties. Indeed, direct administration of NPW into the brain potently reduced seizures in mice. To confirm this discovery, we rationally designed, synthesized, and characterized NPW analogues that exhibited anticonvulsant activities following systemic administration. Our results suggest that the combination of neuropeptide repositioning and engineering NPW analogues that penetrate the blood-brain barrier could provide new drug leads, not only for the treatment of epilepsy and pain but also for studying effects of this peptide on regulating feeding and energy metabolism coupled to leptin levels in the brain.

Distribution of neuropeptide W in the rat brain

Neuropeptide W (NPW), which was recently isolated from the porcine hypothalamus, has been identified as the endogenous ligand of the orphan G protein-coupled receptors GPR7 (NPBWR1) and GPR8 (NPBWR2). Infusion of NPW increases food intake in the light phase, whereas in the dark phase, it has the opposite effect. In this study, we used RT-PCR analysis to examine the gene expression of NPW mRNA in the rat brain, and performed a detailed analysis of the distribution of NPW-positive neurons by use of immunohistochemistry at both the light and electron microscopic levels. NPW mRNA expression was demonstrated in the hypothalamic paraventricular nucleus (PVN), arcuate nucleus (ARC), ventromedial nucleus (VMH) and lateral hypothalamus (LH). At the light microscopic level, NPW-like immunoreactive (NPW-LI) cell bodies were found in the preoptic area (POA), PVN, ARC, VMH, LH, PMD (dorsal premammillary nucleus), periaqueductal gray (PAG), lateral parabrachial nucleus (LPB), and prepositus nucleus (Pr). NPW-LI axon terminals were shown in the POA, bed nucleus of the stria terminalis (BST), amygdala, PVN, ARC, VMH, LH, and PAG, LPB. In addition, at the electron microscopic level, NPW-LI cell bodies and dendritic processes were often seen to receive inputs from other unknown neurons in the ARC, PVN, VMH and amygdala. Our observations indicate that NPW-LI neurons widely distributed in the rat brain region. These finding suggest that NPW may have important roles in feeding behavior, energy homeostasis, emotional response and regulation of saliva secretion.

The propeptide precursor proSAAS is involved in fetal neuropeptide processing and body weight regulation

Mice with a targeted mutation in proSAAS have been generated to investigate whether peptides derived from this precursor could function as an inhibitor of prohormone convertase 1/3 (PC1/3) in vivo as well as to determine any alternate roles for proSAAS in nervous and endocrine tissues. Fetal mice lacking proSAAS exhibit complete, adult-like processing of prodynorphin in the prenatal brain instead of the incomplete processing seen in the brains of wild-type fetal mice where inhibitory proSAAS intermediates are transiently accumulated. This study provides evidence that proSAAS is directly involved in the prenatal regulation of neuropeptide processing in vivo. However, adult mice lacking proSAAS have normal levels of all peptides detected using a peptidomics approach, suggesting that PC1/3 activity is not affected by the absence of proSAAS in adult mice. ProSAAS knockout mice exhibit decreased locomotion and a male-specific 10-15% decrease in body weight, but maintain normal fasting blood glucose levels and are able to efficiently clear glucose from the blood in response to a glucose challenge. This work suggests that proSAAS-derived peptides can inhibit PC1/3 in embryonic brain, but in the adult brain proSAAS peptides may function as neuropeptides that regulate body weight and potentially other behaviors.

Increased physical activity cosegregates with higher intake of carbohydrate and total calories in a subcongenic mouse strain

C57BL/6 J (B6) and CAST/EiJ (CAST), the inbred strain derived from M. musculus castaneus, differ in nutrient intake behaviors, including dietary fat and carbohydrate consumption in a two-diet-choice paradigm. Significant quantitative trait loci (QTLs) for carbohydrate (Mnic1) and total energy intake (Kcal2) are present between these strains on chromosome (Chr) 17. Here we report the refinement of the Chr 17 QTL in a subcongenic strain of the B6.CAST-( D17Mit19-D17Mit91 ) congenic mice described previously. This new subcongenic strain possesses CAST Chr 17 donor alleles from 4.8 to 45.4 Mb on a B6 background. Similar to CAST, the subcongenic mice exhibit increased carbohydrate and total calorie intake per body weight, while fat intake remains equivalent. Unexpectedly, this CAST genomic segment also confers two new physical activity phenotypes: 22% higher spontaneous physical activity levels and significantly increased voluntary wheel-running activity compared with the parental B6 strain. Overall, these data suggest that gene(s) involved in carbohydrate preference and increased physical activity are contained within the proximal region of Chr 17. Interval-specific microarray analysis in hypothalamus and skeletal muscle revealed differentially expressed genes within the subcongenic region, including neuropeptide W (Npw); glyoxalase I (Glo1); cytochrome P450, family 4, subfamily f, polypeptide 1 (Cyp4f15); phospholipase A2, group VII (Pla2g7); and phosphodiesterase 9a (Pde9a). This subcongenic strain offers a unique model for dissecting the contributions and possible interactions among genes controlling food intake and physical activity, key components of energy balance.

Neuropeptide W has cell phenotype-specific effects on the excitability of different subpopulations of paraventricular nucleus neurones

The administration of the neuropeptide W (NPW) and neuropeptide B (NPB) in rodents has been shown to influence the activity of a variety of autonomic and neuroendocrine systems. The paraventricular nucleus (PVN) is a major autonomic and neuroendocrine integration site in the hypothalamus, and neurones within this nucleus express the receptor for these ligands, NPB/W receptor 1 (NPBWR1). In the present study, we used whole cell patch clamp recordings coupled with single-cell reverse transcriptase-polymerase chain reaction to examine the effects of neuropeptide W-23 (NPW-23) on the excitability of identified PVN neurones. Oxytocin, vasopressin and thyrotrophin-releasing hormone neurones were all found to be responsive to 10 nm NPW-23, although both depolarising and hyperpolarising effects were observed in each of these cell groups. By contrast, corticotrophin-releasing hormone cells were unaffected. Further subdivision of chemically phenotyped cell groups into magnocellular, neuroendocrine or pre-autonomic neurones, using their electrophysiological fingerprints, revealed that neurones projecting to medullary and spinal targets were predominantly inhibited by NPW-23, whereas those that projected to median eminence or neural lobe showed almost equivalent numbers of depolarising and hyperpolarising cells. The demonstration of particular phenotypic populations of PVN neurones showing NPW-induced effects on excitability reinforces the importance of the NPB/NPW neuropeptide system as a regulator of autonomic function.

Evolution of vertebrate opioid receptors

The opioid peptides and receptors have prominent roles in pain transmission and reward mechanisms in mammals. The evolution of the opioid receptors has so far been little studied, with only a few reports on species other than tetrapods. We have investigated species representing a broader range of vertebrates and found that the four opioid receptor types (delta, kappa, mu, and NOP) are present in most of the species. The gene relationships were deduced by using both phylogenetic analyses and chromosomal location relative to 20 neighboring gene families in databases of assembled genomes. The combined results show that the vertebrate opioid receptor gene family arose by quadruplication of a large chromosomal block containing at least 14 other gene families. The quadruplication seems to coincide with, and, therefore, probably resulted from, the two proposed genome duplications in early vertebrate evolution. We conclude that the quartet of opioid receptors was already present at the origin of jawed vertebrates approximately 450 million years ago. A few additional opioid receptor gene duplications have occurred in bony fishes. Interestingly, the ancestral receptor gene duplications coincide with the origin of the four opioid peptide precursor genes. Thus, the complete vertebrate opioid system was already established in the first jawed vertebrates.

The relative impact of chronic food restriction and acute food deprivation on plasma hormone levels and hypothalamic neuropeptide expression

Our understanding of the central regulation of food intake and body weight has increased tremendously through implication of a high number of neuropeptides. However, lack of all-embracing studies have made comparison difficult in the past. The objective of this study was to demonstrate the relative importance of the different neuropeptides in terms of involvement in appetite regulatory mechanisms. We quantified expression levels of 21 hypothalamic neuropeptides and circulating levels of leptin, insulin, corticosterone, adrenocorticotropic hormone, ghrelin and adiponectin in rats after acute food deprivation and chronic food restriction using validated quantitative real-time PCR and hormone measurements. Body weight, insulin and leptin were reduced whereas corticosterone was increased by both acute food deprivation and chronic food restriction. Our results confirmed the relative importance in body weight homeostasis of neuropeptide Y and proopiomelanocortin, which were increased and decreased as predicted. The expression of other neuropeptides previously attributed central roles in body weight homeostasis, e.g. melanin-concentrating hormone and orexin, appeared to be less affected by the treatments. Moreover, the expression of dynorphin, galanin-like peptide and neuropeptide B was dramatically reduced after both treatments. This suggests that the latter neuropeptides--although previously known to be involved in body weight homeostasis--may be of unexpected importance in states of negative energy balance.

Food-intake-regulating-neuropeptides are expressed and regulated through pregnancy and following food restriction in rat placenta

BACKGROUND

Neuropeptide Y (NPY), agouti related peptide (AgRP), cocaine and amphetamine-regulated transcript (CART) and melanocortins, the products of the proopiomelanocortin (POMC), are hypothalamic peptides involved in feeding regulation and energy homeostasis. Recent evidence has demonstrated their expression in rat and human placenta.

METHODS

In the current study, we have investigated the expression of those neuropeptides in the rat placenta by real-time PCR using a model of maternal food restriction.

RESULTS

Our results showed that placental-derived neuropeptides were regulated through pregnancy and following food restriction.

CONCLUSION

These data could indicate that placental-derived neuropeptides represent a local regulatory circuit that may fine-tune control of energy balance during pregnancy.

Neuronal interactions between neuropeptide W- and orexin- or melanin-concentrating hormone-containing neurons in the rat hypothalamus

Neuropeptide W (NPW) was recently discovered as the endogenous ligand for GPR7 and GPR8, which are orphan G protein-coupled receptors isolated from the porcine brain. These receptors are assumed to be involved in feeding regulation and/or energy homeostasis. Recent anatomical studies have revealed that high levels of GPR7 mRNA are distributed in the brain, including the hypothalamus and amygdala. However immunohistochemical studies on the distribution and localization of NPW have revealed differing results concerning whether or not NPW-containing cell bodies and their processes are present in the hypothalamus. Only a few immunohistochemical reports have been published concerning the presence of NPW-containing neurons in the brains of rodents, while there have been no anatomical studies of the co-localization of this neuropeptide with other transmitters. On this basis, we used a specific antiserum against NPW to determine immunohistochemically the presence of NPW-containing neurons in the rat hypothalamus. Many NPW-like immunoreactive cell bodies and their processes could be detected in the caudal region of the lateral hypothalamus but not in its anterior or middle regions. Given this positive identification of NPW-containing neurons in the lateral hypothalamus, we further studied the nature of interaction between NPW-containing neurons and neurons containing feeding regulating peptides such as orexin- and melanin-concentrating hormone (MCH). Very close interactions between NPW-containing nerve processes and orexin- and MCH-containing neuronal cell bodies and processes could be observed. These morphological findings strongly suggest that NPW is involved in the regulation of feeding and/or sleep/arousal behavior through orexin- and/or MCH-mediated neuronal pathways.

Development of a potent and selective GPR7 (NPBW1) agonist: a systematic structure–activity study of neuropeptide B

Neuropeptide B (NPB) has been recently identified as an endogenous ligand for GPR7 (NPBW1) and GPR8 (NPBW2) and has been shown to possess a relatively high selectivity for GPR7. In order to identify useful experimental tools to address physiological roles of GPR7, we synthesized a series of NPB analogs based on modification of an unbrominated form of 23 amino acids with amidated C-terminal, Br(-)NPB-23-NH(2). We confirmed that truncation of the N-terminal Trp residue resulted in almost complete loss of the binding affinity of NPB for GPR7 and GPR8, supporting the special importance of this residue for binding. Br(-)NPB-23-NH2 analogs in which each amino acid in positions 4, 5, 7, 8, 9, 10, 12 and 21 was replaced with alanine or glycine exhibited potent binding affinity comparable to the parent peptide. In contrast, replacement of Tyr(11) with alanine reduced the binding affinity for both GPR7 and GPR8 four fold. Of particular interest, several NPB analogs in which the consecutive amino acids from Pro4 to Val(13) were replaced with several units of 5-aminovaleric acid (Ava) linkers retained their potent affinity for GPR7. Furthermore, these Ava-substituted NPB analogs exhibited potent agonistic activities for GPR7 expressed in HEK293 cells. Among the Ava-substituted NPB analogs, analog 15 (Ava-5) and 17 (Ava-3) exhibited potency comparable to the parent peptide for GPR7 with significantly reduced activity for GPR8, resulting in high selectivity for GPR7. These highly potent and selective NPB analogs may be useful pharmacological tools to investigate the physiological and pharmacological roles of GPR7.