Recent advances in mammalian RFamide peptides: the discovery and functional analyses of PrRP, RFRPs and QRFP

Structure and dynamics of the pyroglutamylated RF-amide peptide QRFP receptor GPR103

Pyroglutamylated RF-amide peptide (QRFP) is a peptide hormone with a C-terminal RF-amide motif. QRFP selectively activates a class A G-protein-coupled receptor (GPCR) GPR103 to exert various physiological functions such as energy metabolism and appetite regulation. Here, we report the cryo-electron microscopy structure of the QRFP26-GPR103-Gq complex at 3.19 Å resolution. QRFP26 adopts an extended structure bearing no secondary structure, with its N-terminal and C-terminal sides recognized by extracellular and transmembrane domains of GPR103 respectively. This movement, reminiscent of class B1 GPCRs except for orientation and structure of the ligand, is critical for the high-affinity binding and receptor specificity of QRFP26. Mutagenesis experiments validate the functional importance of the binding mode of QRFP26 by GPR103. Structural comparisons with closely related receptors, including RY-amide peptide-recognizing GPCRs, revealed conserved and diversified peptide recognition mechanisms, providing profound insights into the biological significance of RF-amide peptides. Collectively, this study not only advances our understanding of GPCR-ligand interactions, but also paves the way for the development of novel therapeutics targeting metabolic and appetite disorders and emergency medical care.

A Brain Region-Dependent Alteration in the Expression of Vasopressin, Corticotropin-Releasing Factor, and Their Receptors Might Be in the Background of Kisspeptin-13-Induced Hypothalamic-Pituitary-Adrenal Axis Activation and Anxiety in Rats

Previously, we reported that intracerebroventricularly administered kisspeptin-13 (KP-13) induces anxiety-like behavior and activates the hypothalamic-pituitary-adrenal (HPA) axis in rats. In the present study, we aimed to shed light on the mediation of KP-13's stress-evoking actions. The relative gene expressions of the corticotropin-releasing factor (Crf, Crfr1, and Crfr2) and arginine vasopressin (Avp, Avpr1a, and Avpr1b) systems were measured in the amygdala and hippocampus of male Wistar rats after icv KP-13 treatment. CRF and AVP protein content were also determined. A different set of animals received CRF or V1 receptor antagonist pretreatment before the KP-13 challenge, after which either an open-field test or plasma corticosterone levels measurement was performed. In the amygdala, KP-13 induced an upregulation of Avp and Avpr1b expression, and a downregulation of Crf. In the hippocampus, the mRNA level of Crf increased and the level of Avpr1a decreased. A significant rise in AVP protein content was also detected in the amygdala. KP-13 also evoked anxiety-like behavior in the open field test, which the V1 receptor blocker antagonized. Both CRF and V1 receptor blockers reduced the KP-13-evoked rise in the plasma corticosterone level. This suggests that KP-13 alters the AVP and CRF signaling and that might be responsible for its effect on the HPA axis and anxiety-like behavior.

Variation in Hypothalamic GnIH Expression and Its Association with GnRH and Kiss1 during Pubertal Progression in Male Rhesus Monkeys (Macaca mulatta)

Modulation of pulsatile gonadotropin-releasing hormone (GnRH) secretion across postnatal development in higher primates is not fully understood. While gonadotropin-inhibitory hormone (GnIH) is reported to suppress reproductive axis activity in birds and rodents, little is known about the developmental trajectory of GnIH expression in rhesus monkeys throughout the pubertal transition. This study was aimed at examining the variation in GnIH immunoreactivity (-ir) and associated changes among GnIH, GnRH, and Kiss1 mRNA expression in the hypothalamus of infant, juvenile, prepubertal, and adult male rhesus monkeys. The brains from rhesus macaques were collected from infancy until adulthood and were examined using immunofluorescence and RT-qPCR. The mean GnIH-ir was found to be significantly higher in prepubertal animals (p < 0.01) compared to infants, and significantly reduced in adults (p < 0.001). Significantly higher (p < 0.001) GnRH and Kiss1 mRNA expression was noted in adults while GnIH mRNA expression was the highest at the prepubertal stage (p < 0.001). Significant negative correlations were seen between GnIH-GnRH (p < 0.01) and GnIH-Kiss1 (p < 0.001) expression. Our findings suggest a role for GnIH in the prepubertal suppression of the reproductive axis, with disinhibition of the adult reproductive axis occurring through decreases in GnIH. This pattern of expression suggests that GnIH may be a viable target for the development of novel therapeutics and contraceptives for humans.

Functions of habenula in reproduction and socio-reproductive behaviours

Habenula is an evolutionarily conserved structure in the brain of vertebrates. Recent reports have drawn attention to the habenula as a processing centre for emotional decision-making and its role in psychiatric disorders. Emotional decision-making process is also known to be closely associated with reproductive conditions. The habenula receives innervations from reproductive centres within the brain and signals from key reproductive neuroendocrine regulators such as gonadal sex steroids, gonadotropin-releasing hormone (GnRH), and kisspeptin. In this review, based on morphological, biochemical, physiological, and pharmacological evidence we discuss an emerging role of the habenula in reproduction. Further, we discuss the modulatory role of reproductive endocrine factors in the habenula and their association with socio-reproductive behaviours such as mating, anxiety and aggression.

RF-amide related peptide-3 (RFRP-3): a novel neuroendocrine regulator of energy homeostasis, metabolism, and reproduction

A hypothalamic neuropeptide, RF-amide related peptide-3 (RFRP-3), the mammalian ortholog of the avian gonadotropin-inhibitory hormone (GnIH) has inhibitory signals for reproductive axis via G-protein coupled receptor 147 in mammals. Moreover, RFRP-3 has orexigenic action but the mechanism involved in energy homeostasis and glucose metabolism is not yet known. Though, the RFRP-3 modulates orexigenic action in co-operation with other neuropeptides, which regulates metabolic cues in the hypothalamus. Administration of GnIH/RFRP-3 suppresses plasma luteinizing hormone, at the same time stimulates feeding behavior in birds and mammals. Likewise, in the metabolically deficient conditions, its expression is up-regulated suggests that RFRP-3 contributes to the integration of energy balance and reproduction. However, in many other metabolic conditions like induced diabetes and high-fat diet obesity, etc. its role is still not clear while, RFRP-3 induces the glucose homeostasis by adipocytes is reported. The physiological role of RFRP-3 in metabolic homeostasis and the metabolic effects of RFRP-3 signaling in pharmacological studies need a detailed discussion. Further studies are required to find out whether RFRP-3 is associated with restricted neuroendocrine function observed in type II diabetes mellitus, aging, or sub-fertility. In this context, the current review is focused on the role of RFRP-3 in the above-mentioned mechanisms. Studies from search engines including PubMed, Google Scholar, and science.gov are included after following set inclusion/exclusion criteria. As a developing field few mechanisms are still inconclusive, however, based on the available information RFRP-3 seems to be a putative tool in future treatment strategies towards metabolic disease.

Physiological and genomic insight into neuroendocrine regulation of puberty in gilts

The timing of pubertal attainment in gilts is a critical factor for pork production and is an early indicator of future reproductive potential. Puberty, defined as age at first standing estrus in the presence of a boar, is brought about by an escape from estrogen inhibition of the GnRH pulse generator, which allows for increasing LH pulses leading to the onset of cyclicity. The biological mechanisms that control the timing of these events is related to decreasing inhibitory signals with a concomitant increase in stimulatory signals within the hypothalamus. The roles of gamma-aminobutyric acid, endogenous opioid peptides, and gonadotropin-inhibitory hormone in negatively regulating gonadotropin secretion in gilts is explored. Developmental changes in stimulatory mechanisms of glutamatergic and kisspeptin neurons are important for increased LH pulsatility required for the occurrence of puberty in pigs. Age at first estrus of gilts is metabolically gated, and numerous metabolites, metabolic hormones, and appetite-regulating neurotransmitters have been implicated in the nutritional regulation of gonadotropin secretion. Leptin is an important metabolic signal linking body energy reserves with age at puberty in gilts. Leptin acting through neuropeptide Y and proopiomelanocortin neurons in the hypothalamus has important impacts on the function of the reproductive neurosecretory axis of gilts. Age at puberty in swine is heritable, and genomic analyses reveal it to be a polygenic trait. Genome-wide association studies for pubertal age in gilts have revealed several genomic regions in common with those identified for age at menarche in humans. Candidate genes have been identified that have important functions in growth and adiposity. Numerous genes regulating hypothalamic neuronal function, gonadotropes in the adenohypophysis, and ovarian follicular development have been identified and illustrate the complex maturational changes occurring in the hypothalamic-pituitary-ovarian axis during puberty in gilts.

Pyroglutamylated RFamide peptide 43: A putative modulator of testicular steroidogenesis

BACKGROUND

We have recently shown that QRFP and its receptor are predominantly expressed in germ cells, Sertoli cells and Leydig cells in mice testes.

OBJECTIVE

The present study investigated the role of QRFP in testicular steroidogenesis in mice.

MATERIALS AND METHODS

Both ex vivo and in vivo experiments were performed. For ex vivo, testicular tissues were cultured with 0, 10, 100 and 1000 nM QRFP, with or without hCG, for 6, 12 and 24 h, and media were used for testosterone assay. The hCG-stimulated testicular tissues were used for immunoblot of SF1, StAR, CYP11A1, 3β- and 17β-HSD. For in vivo, mice received bilateral intratesticular injection of saline or 0.3, 1 and 3nmol QRFP and were killed at 6, 12 and 24 h post-injection. Testosterone in serum was measured at above durations, while qRT-PCR of HMG-CoA synthase 1 and SR-B1 and immunoblot of steroidogenesis-related markers were performed at 24 h post-injection.

RESULTS

Testosterone production under basal and hCG-stimulated conditions increased in a time-dependent manner, and QRFP supplementation to testicular culture caused an increase and a decrease in hormone production. The effect of QRFP on testosterone production under hCG-stimulated culture or in vivo conditions at 6 and 24h was similar. At 6h, testosterone production increased at 10 and 100 nM and also at 0.3 and 1nmol QRFP, while it decreased at 1000 nM and 3 nmol doses. At 24 h, testosterone level decreased at lower concentrations (10 nM and 0.3 nmol) and thereafter increased at middle (100nM and 1nmol) and higher (1000 nM and 3 nmol) concentrations under both hCG-stimulated culture and in vivo.

DISCUSSION AND CONCLUSION

QRFP induced production of testosterone by modulating steroidogenic machinery at optimal doses and durations. Further, findings of in vivo study indicate that QRFP besides directly regulating testicular steroidogenesis may also have modulated other factors which act together in a holistic manner to control steroidogenesis.

Characterization of the neuropeptide FF (NPFF) gene in chickens: evidence for a single bioactive NPAF peptide encoded by the NPFF gene in birds

The 2 structurally related peptides, neuropeptide FF (NPFF) and neuropeptide AF (NPAF), are encoded by the NPFF gene and have been identified as neuromodulators that regulate nociception and opiate-mediated analgesia via NPFF receptor (NPFFR2) in mammals. However, little is known about these 2 peptides in birds. In this study, we examined the structure, tissue expression profile, and functionality of NPAF and NPFF in chickens. Our results showed that: 1) unlike mammalian NPFF, NPFF from chicken and other avian species is predicted to produce a single bioactive NPAF peptide, whereas the putative avian NPFF peptide likely lacks activity due to the absence of functional RFamide motif at its C-terminus; 2) synthetic chicken (c-) NPAF can potently activate cNPFFR2 (and not cNPFFR1) expressed in HEK293 cells, as monitored by 3 cell-based luciferase reporter systems, indicating that cNPAF is a potent ligand for cNPFFR2, which activation could decrease intracellular cAMP levels and stimulate the MAPK/ERK signaling cascade; interestingly, gonadotropin-inhibitory hormone, a peptide sharing high structural similarity to NPAF, could specifically activate cNPFFR1 (but not cNPFFR2); 3) Quantitative real-time PCR revealed that cNPFF mRNA is widely expressed in chicken tissues with the highest level detected in the hypothalamus, whereas cNPFFR2 is expressed in all tissues examined with the highest level noted in the hypothalamus and anterior pituitary. Taken together, our data reveal that avian NPFF encodes a single bioactive NPAF peptide, which preferentially activates NPFFR2, and provides insights into potential structural and functional changes of NPFF-derived peptides during vertebrate evolution.

The kisspeptin derivative kissorphin reduces the acquisition, expression, and reinstatement of ethanol-induced conditioned place preference in rats

Research has shown that opioids are involved in the rewarding effects of ethanol. Neuropeptide FF (NPFF) has been described as an anti-opioid peptide because, in many cases, it inhibits opioid and ethanol effects in rodents. Kissorphin (KSO) is a new peptide derived from kisspeptin-10 with structural similarities to NPFF. This peptide possesses NPFF-like biological activity in vitro. The aim of the current study was to investigate whether KSO (Tyr-Asn-Trp-Asn-Ser-Phe-NH2) influences the acquisition, expression, and reinstatement of ethanol-induced conditioned place preference (ethanol-CPP) in rats. The ethanol-CPP was established (conditioning for 5 days) by intraperitoneal (i.p.) administration of ethanol (1 g/kg, 20%, w/v) using an unbiased procedure. After that, one group of rats was used in final post-conditioning testing (expression of CPP) and the other group received a priming injection of ethanol after 10 days of extinction (reinstatement of CPP). Our experiments showed that KSO, given intravenously (i.v.) at the doses of 1, 3, and 10 nmol before every ethanol administration, inhibited the acquisition and, given acutely before the post-conditioning test or before the priming dose of ethanol, inhibited the expression and reinstatement of ethanol-CPP, respectively, in a dose-dependent manner. KSO given by itself neither induced place preference nor aversion and did not alter locomotor activity and coordination of rats. These results suggest that KSO can alter rewarding/motivational effects of ethanol. These data suggest this peptide possesses an anti-opioid character.

QRFP administration into the medial hypothalamic nuclei improves memory in rats

Even though several of RFamide peptides have been shown to modify memory and learning processes in different species, almost nothing is known regarding cognitive effects of recently discovered neuropeptide QRFP. Considering multiple physiological functions of QRFP, localization of QRFP-synthesizing neurons in the hypothalamus and its' widely spread binding sites within the CNS, the present study was designed to investigate the possible role of QRFP in the consolidation of spatial memory. As target area for microinjection, the medial hypothalamic area, including dorsomedial (DMN) and ventromedial (VMN) nuclei, has been chosen. At first, the effects of two doses (200 ng and 400 ng) of QRFP were investigated in Morris water maze. After that receptor antagonist BIBP3226 (equimolar amount to the effective dose of neuropeptide) was applied to elucidate whether it can prevent effects of QRFP. To reveal possible changes in anxiety level, animals were tested in Elevated plus maze. The higher dose of QRFP (400 ng) improved short-term memory consolidation in Morris water maze. Pretreatment with antagonist BIBP3226 abolished cognitive effects of QRFP. The neuropeptide did not affect anxiety level of rats. This study provides unique evidence regarding the role of QRFP in the consolidation of memory and gives the basis for further investigations of neuropeptide's cognitive effects.

Functional identification of an FMRFamide-related peptide gene on diapause induction of the migratory locust, Locusta migratoria L

FMRFamide-related peptides (FaRPs) are a type of neuropeptide, which participate in a variety of physiological processes in insects. Previous study showed that myosuppressin, being a member of FaRPs, initiated pupal diapause in Mamestra brassicae. We presumed that FaRPs genes might play a critical role in photoperiodic diapause induction of L. migratoria. To verify our hypothesis, flrf, a precursor gene of FaRP from L. migratoria, was initially cloned under long and short photoperiods that encoded by flrf gene identified from central nervous system (CNS). Phylogenetic analysis showed that the protein encoded by L. migratoria flrf gene, clustered together with Nilaparvata lugens (Hemiptera: Delphacidae) with 100% bootstrap support, was basically an FMRFamide precursor homologue. We noticed the availability of -RFamide peptides (GSERNFLRFa, DRNFIRFa) under short photoperiod only, which suggested their functions related to photoperiodic diapause induction. RNAi and quantitative real-time PCR (qRT-PCR) results further confirmed that the flrf gene promoted locust's diapause.

The role of kisspeptin system in cancer biology

Kisspeptins are a family of neuropeptides that are known to be critical in puberty initiation and ovulation. Apart from that kisspeptin derived peptides (KPs) are also known for their antimetastatic activities in several malignancies. Herein we report recent evidence of the role of kisspeptins in cancer biology and we examine the prospective of targeting the kisspeptin pathways leading to a better prognosis in patients with malignant diseases.

Beetles as Model Organisms in Physiological, Biomedical and Environmental Studies - A Review

Model organisms are often used in biological, medical and environmental research. Among insects, Drosophila melanogaster, Galleria mellonella, Apis mellifera, Bombyx mori, Periplaneta americana, and Locusta migratoria are often used. However, new model organisms still appear. In recent years, an increasing number of insect species has been suggested as model organisms in life sciences research due to their worldwide distribution and environmental significance, the possibility of extrapolating research studies to vertebrates and the relatively low cost of rearing. Beetles are the largest insect order, with their representative - Tribolium castaneum - being the first species with a completely sequenced genome, and seem to be emerging as new potential candidates for model organisms in various studies. Apart from T. castaneum, additional species representing various Coleoptera families, such as Nicrophorus vespilloides, Leptinotarsa decemlineata, Coccinella septempunctata, Poecilus cupreus, Tenebrio molitor and many others, have been used. They are increasingly often included in two major research aspects: biomedical and environmental studies. Biomedical studies focus mainly on unraveling mechanisms of basic life processes, such as feeding, neurotransmission or activity of the immune system, as well as on elucidating the mechanism of different diseases (neurodegenerative, cardiovascular, metabolic, or immunological) using beetles as models. Furthermore, pharmacological bioassays for testing novel biologically active substances in beetles have also been developed. It should be emphasized that beetles are a source of compounds with potential antimicrobial and anticancer activity. Environmental-based studies focus mainly on the development and testing of new potential pesticides of both chemical and natural origin. Additionally, beetles are used as food or for their valuable supplements. Different beetle families are also used as bioindicators. Another important research area using beetles as models is behavioral ecology studies, for instance, parental care. In this paper, we review the current knowledge regarding beetles as model organisms and their practical application in various fields of life science.

Emerging Genetic and Epigenetic Mechanisms Underlying Pubertal Maturation in Adolescence

The adolescent transition begins with the onset of puberty which, upstream in the brain, is initiated by the gonadotropin-releasing hormone (GnRH) pulse generator that activates the release of peripheral sex hormones. Substantial research in human and animal models has revealed a myriad of cellular networks and heritable genes that control the GnRH pulse generator allowing the individual to begin the process of reproductive competence and sexual maturation. Here, we review the latest knowledge in neuroendocrine pubertal research with emphasis on genetic and epigenetic mechanisms underlying the pubertal transition.

The neuropeptides of Asian freshwater clam (Corbicula fluminea) as new molecular biomarker basing on the responses of organophosphate chemicals exposure

In the present study, to discover new biomarker of Asian freshwater clam (Corbicula fluminea) to assess impact of environmental pollutions, cholecystokinin (CCK), conopressin, and Neuropeptide FF (FFamide) in C. fluminea were selected as potent biomarkers. Therefore, their full-length cDNAs were cloned and characterized to investigate the molecular characteristics and expression patterns of neuropeptides in C. fluminea. According to the sequence analysis, CCK, conopressin, and FFamide encoded proteins of 173, 152, and 90 amino acids, respectively. Moreover, the multiple sequence alignment revealed that the bioactive regions of these neuropeptides were well conserved among different invertebrates. In addition, under basal conditions, CCK, conopressin and FFamide mRNA were mainly expressed in the visceral mass, whereas the FFamide mRNA was rarely detected in the foot and mantle. Exposure to 20 and 200 μg/L Tris (2-butoxyethyl) phosphate (TBOEP) and tri-butyl-phosphate (TBP) exposure significantly up-regulated the expression of the CCK and FFamide mRNAs in the visceral mass (p < 0.05), whereas no significant changes in conopressin mRNA levels were observed in response to any treatment. Therefore, CCK and FFamide of C. fluminea neuropeptides are feasible new biomarkers for screening and assessing responses to organophosphate chemicals.

Orphan G protein-coupled receptors: The role in CNS disorders

There are various types of receptors in the central nervous system (CNS). G protein-coupled receptors (GPCRs) have the highest expression with a wide range of physiological functions. A newer sub group of these receptors namely orphan GPCRs have been discovered. GPR3, GPR6, GPR17, GPR26, GPR37, GPR39, GPR40, GPR50, GPR52, GPR54, GPR55, GPR85, GPR88, GPR103, and GPR139 are the selected orphan GPCRs for this article. Their roles in the central nervous system have not been understood well so far. However, recent studies show that they may have very important functions in the CNS. Hence, in the present study, we reviewed most recent findings regarding the physiological roles of the selected orphan GPCRs in the CNS. After a brief presentation of each receptor, considering the results from genetic and pharmacological manipulation of the receptors, their roles in the pathophysiology of different diseases and disorders including anxiety, depression, schizophrenia, epilepsy, Alzheimer's disease, Parkinson's disease, and substance abuse will be discussed. At present, our knowledge regarding the role of GPCRs in the brain is very limited. However, previous limited studies show that orphan GPCRs have an important place in psychopharmacology and these receptors are potential new targets for the treatment of major CNS diseases.

Is precocious puberty linked to hypothalamic expression of arginine-phenylalanine-amide-related peptide?

The up-regulation and down-regulation of gonadotropin-releasing hormone (GnRH) in central precocious puberty is not yet known. However, recent advances in neuroendocrinology have shown the controlling role of arginine-phenylalanine RF-amide-related peptides (RFRPs) on GnRH secretion in different phenomenon of reproduction such as estrus cycle and pregnancy, but the exact role of RFRPs in puberty and its related pathologic condition, precocious puberty, is not clear yet. This paper hypothesizes that RFRP is a regulatory peptide of puberty and might prevent the precocious puberty. On the basis of previous studies on hormonal fluctuations at the time of puberty, RFRP might have a role on controlling of premature secretion of GnRH and avoiding central precocious puberty.

Discovery of Novel Proline-Based Neuropeptide FF Receptor Antagonists

The neuropeptide FF (NPFF) system has been implicated in a number of physiological processes including modulating the pharmacological activity of opioid analgesics and several other classes of drugs of abuse. In this study, we report the discovery of a novel proline scaffold with antagonistic activity at the NPFF receptors through a high throughput screening campaign using a functional calcium mobilization assay. Focused structure-activity relationship studies on the initial hit 1 have resulted in several analogs with calcium mobilization potencies in the submicromolar range and modest selectivity for the NPFF1 receptor. Affinities and potencies of these compounds were confirmed in radioligand binding and functional cAMP assays. Two compounds, 16 and 33, had good solubility and blood-brain barrier permeability that fall within the range of CNS permeant candidates without the liability of being a P-glycoprotein substrate. Finally, both compounds reversed fentanyl-induced hyperalgesia in rats when administered intraperitoneally. Together, these results point to the potential of these proline analogs as promising NPFF receptor antagonists.

The Arg-Phe-amide peptide 26RFa/glutamine RF-amide peptide and its receptor: IUPHAR Review 24

The RFamide neuropeptide 26RFa was first isolated from the brain of the European green frog on the basis of cross-reactivity with antibodies raised against bovine neuropeptide FF (NPFF). 26RFa and its N-terminally extended form glutamine RF-amide peptide (QRFP) have been identified as cognate ligands of the former orphan receptor GPR103, now renamed glutamine RF-amide peptide receptor (QRFP receptor). The 26RFa/QRFP precursor has been characterized in various mammalian and non-mammalian species. In the brain of mammals, including humans, 26RFa/QRFP mRNA is almost exclusively expressed in hypothalamic nuclei. The 26RFa/QRFP transcript is also present in various organs especially in endocrine glands. While humans express only one QRFP receptor, two isoforms are present in rodents. The QRFP receptor genes are widely expressed in the CNS and in peripheral tissues, notably in bone, heart, kidney, pancreas and testis. Structure-activity relationship studies have led to the identification of low MW peptidergic agonists and antagonists of QRFP receptor. Concurrently, several selective non-peptidic antagonists have been designed from high-throughput screening hit optimization. Consistent with the widespread distribution of QRFP receptor mRNA and 26RFa binding sites, 26RFa/QRFP exerts a large range of biological activities, notably in the control of energy homeostasis, bone formation and nociception that are mediated by QRFP receptor or NPFF2. The present report reviews the current knowledge concerning the 26RFa/QRFP-QRFP receptor system and discusses the potential use of selective QRFP receptor ligands for therapeutic applications.

NPFFR2 Activates the HPA Axis and Induces Anxiogenic Effects in Rodents

Neuropeptide FF (NPFF) belongs to the RFamide family and is known as a morphine-modulating peptide. NPFF regulates various hypothalamic functions through two receptors, NPFFR1 and NPFFR2. The hypothalamic-pituitary-adrenal (HPA) axis participates in physiological stress response by increasing circulating glucocorticoid levels and modulating emotional responses. Other RFamide peptides, including neuropeptide AF, neuropeptide SF and RFamide related peptide also target NPFFR1 or NPFFR2, and have been reported to activate the HPA axis and induce anxiety- or depression-like behaviors. However, little is known about the action of NPFF on HPA axis activity and anxiety-like behaviors, and the role of the individual receptors remains unclear. In this study, NPFFR2 agonists were used to examine the role of NPFFR2 in activating the HPA axis in rodents. Administration of NPFFR2 agonists, dNPA (intracerebroventricular, ICV) and AC-263093 (intraperitoneal, IP), time-dependently (in rats) and dose-dependently (in mice) increased serum corticosteroid levels and the effects were counteracted by the NPFF receptor antagonist, RF9 (ICV), as well as corticotropin-releasing factor (CRF) antagonist, α-helical CRF(9-41) (intravenous, IV). Treatment with NPFFR2 agonist (AC-263093, IP) increased c-Fos protein expression in the hypothalamic paraventricular nucleus and induced an anxiogenic effect, which was evaluated in mice using an elevated plus maze. These findings reveal, for the first time, that the direct action of hypothalamic NPFFR2 stimulates the HPA axis and triggers anxiety-like behaviors.

Effects of RFamide-related peptide-1 (RFRP-1) microinjections into the central nucleus of amygdala on passive avoidance learning in rats

The amygdaloid body (AMY) plays an important role in memory, learning and reward-related processes. RFRP-1 immunoreactive fibers and NPFF receptors were identified in the AMY, and previously we verified that RFRP-1 infused into the central nucleus of AMY (CeA) induced place preference. The aim of the present study was to examine the possible effects of RFRP-1 in the CeA on passive avoidance learning. Male Wistar rats were examined in two-compartment passive avoidance paradigm. Animals were shocked with 0.5mA current and subsequently were microinjected bilaterally with 50ng or 100ng RFRP-1 in volume of 0.4μl, or 20ng NPFF receptor antagonist RF9 (ANT) alone, or antagonist 15min before 50ng RFRP-1 treatments into the CeA. Fifty nanogram dose of RFRP-1 significantly increased the step-through latency time, the 100ng RFRP-1 and the ANT alone were ineffective. The effect of 50ng RFRP-1 was eliminated by the ANT pretreatment. Our results suggest that intraamygdaloid RFRP-1 enhances learning processes and memory in aversive situations and this effect can specifically be prevented by ANT pretreatment.

Antibiotics and specialized metabolites from the human microbiota

Human microbiota associated with each body site produce specialized molecules to kill human pathogens. Advanced bioinformatics tools will help to discover unique microbiome chemistry.

Non-proton ligand-sensing domain of acid-sensing ion channel 3 is required for itch sensation

Itch, the unpleasant sensation that evokes a desire to scratch, accompanies numerous skin and nervous system disorders. However, the molecular mechanisms of itch are unclear. Acid-sensing ion channel 3 (ASIC3) is a sensor of acidic and primary inflammatory pain. The whole-cell patch clamp technique was used to determine the effect of chloroquine (CQ) on ASICs currents in primary sensory neurons or the Chinese hamster ovary cells transfected with rat ASIC1a or ASIC3. Site-directed mutagenesis of plasmid was performed. Scratching behavior was evaluated by measuring the number of bouts during 30 min after injection. CQ, an anti-malarial drug defined as a histamine-independent pruritogen, selectively enhanced the sustained phase of ASIC3 current in a concentration-dependent manner either in ASIC3-transfected Chinese hamster ovary cells or in primary cultured rat dorsal root ganglion neurons. Further studies revealed that the effect of CQ on ASIC3 channels depends on the newly identified non-proton ligand-sensing domain. Importantly, CQ-evoked scratching behavior was largely alleviated by APETx2, a selective ASIC3 channel blocker. Like CQ, other compounds such as amiloride, 2-guanidine-4-methylquinazoline and neuropeptide FF, which have been previously reported to be non-proton ligands that activate ASIC3, undoubtedly evoked the scratching response. In conclusion, ASIC3, a proton-gated ion channel critical for pain sensation, also functions as an essential component of itch transduction.

In vivo and vitro characterization of the effects of kisspeptin-13, endogenous ligands for GPR54, on mouse gastrointestinal motility

Kisspeptin (KP), the endogenous ligand of GPR54, is a mammalian amidated neurohormone, which belongs to the RF-amide peptide family. However, in contrast with the related members of the RF-amide family, little information is available regarding its role in the gastrointestinal motility. With regard to the recent data suggesting KP play an important role in food intake, and while gastrointestinal motility are closely related to it. Thus, in the present work, effects of central administration of KP-13, one of the endogenous active isoforms, on gastrointestinal motility were investigated. The results indicated that intracerebroventricular (i.c.v.) infused of KP-13 significantly facilitated gastrointestinal transit, bead expulsion and fecal pellet output, respectively, while has no effect on gastric emptying. The effects were significantly reversed by GPR54 antagonist 234, but not GnRH receptor antagonist Cetrorelix. However, i.p. injected of KP-13 or compound 5 (10mg/kg), a high metabolic stability kisspeptin analog, did not affect gastrointestinal transit, suggesting that KP-13 or compound 5 facilitated gastrointestinal transit through the activation of central GPR54. Then the gastrointestinal motility-enhancing effects were also presented after infusion of KP-13 into the hypothalamus. In vitro, KP-13 (10^-6M) also modulated colonic contraction, but not in the stomach and small intestine. Similarly, KP-13 (10^-6M)-induced contractions of circular and longitudinal colonic muscle were significantly attenuated by antagonist 234 (10^-6M). In conclusion, all the results indicated that KP-13 promoted gastrointestinal motility through the activation of GPR54, which implicate that KP/GPR54 system might be a new target to treat gastrointestinal function disorder.

Identification of Potential Key Long Non-Coding RNAs and Target Genes Associated with Pneumonia Using Long Non-Coding RNA Sequencing (lncRNA-Seq): A Preliminary Study

Background

This study aimed to identify the potential key long non-coding RNAs (lncRNAs) and target genes associated with pneumonia using lncRNA sequencing (lncRNA-seq).

Material/Methods

A total of 9 peripheral blood samples from patients with mild pneumonia (n=3) and severe pneumonia (n=3), as well as volunteers without pneumonia (n=3), were received for lncRNA-seq. Based on the sequencing data, differentially expressed lncRNAs (DE-lncRNAs) were identified by the limma package. After the functional enrichment analysis, target genes of DE-lncRNAs were predicted, and the regulatory network was constructed.

Results

In total, 99 DE-lncRNAs (14 upregulated and 85 downregulated ones) were identified in the mild pneumonia group and 85 (72 upregulated and 13 downregulated ones) in the severe pneumonia group, compared with the control group. Among these DE-lncRNAs, 9 lncRNAs were upregulated in both the mild and severe pneumonia groups. A set of 868 genes were predicted to be targeted by these 9 DE-lncRNAs. In the network, RP11-248E9.5 and RP11-456D7.1 targeted the majority of genes. RP11-248E9.5 regulated several genes together with CTD-2300H10.2, such as QRFP and EPS8. Both upregulated RP11-456D7.1 and RP11-96C23.9 regulated several genes, such as PDK2. RP11-456D7.1 also positively regulated CCL21.

Conclusions

These novel lncRNAs and their target genes may be closely associated with the progression of pneumonia.

Anxiolytic effect of the GPR103 receptor agonist peptide P550 (homolog of neuropeptide 26RFa) in mice. Involvement of neurotransmitters

The GPR103 receptor is a G protein-coupled receptor, which plays a role in several physiological functions. However, the role of the GPR103 receptor in anxiety has not been clarified. The first aim of our study was to elucidate the involvement of the GPR103 receptor in anxious behavior. Mice were treated with peptide P550, which is the mouse homolog of neuropeptide 26RFa and has similar activity for the GPR103 receptor as neuropeptide 26RFa. The anxious behavior was investigated using an elevated plus-maze paradigm. The second aim of our study was to investigate the underlying neurotransmissions. Accordingly, mice were pretreated with a nonselective muscarinic acetylcholine receptor antagonist, atropine, a γ-aminobutyric acid subunit A (GABAA) receptor antagonist, bicuculline, a non-selective 5-HT2 serotonergic receptor antagonist, cyproheptadine, a mixed 5-HT1/5-HT2 serotonergic receptor antagonist, methysergide, a D2, D3, D4 dopamine receptor antagonist, haloperidol, a nonselective α-adrenergic receptor antagonist, phenoxybenzamine and a nonselective β-adrenergic receptor antagonist, propranolol. Our results demonstrated that peptide P550 reduces anxious behavior in elevated plus maze test in mice. Our study shows also that GABAA-ergic, α- and β-adrenergic transmissions are all involved in this action, whereas 5-HT1 and 5-HT2 serotonergic, muscarinic cholinergic and D2, D3, D4 dopaminergic mechanisms may not be implicated.

The effects of high fat diet and estradiol on hypothalamic prepro-QRFP mRNA expression in female rats

Estradiol (E2) is a potent regulator of feeding behavior, body weight and adiposity in females. The hypothalamic neuropeptide, QRFP, is an orexigenic peptide that increases the consumption of high fat diet (HFD) in intact female rats. Therefore, the goal of the current series of studies was to elucidate the effects of E2 on the expression of hypothalamic QRFP and its receptors, QRFP-r1 and QRFP-r2, in female rats fed a HFD. Alterations in prepro-QRFP, QRFP-r1, and QRFP-r2 expression across the estrous cycle, following ovariectomy (OVX) and following estradiol benzoate (EB) treatment were assessed in the ventral medial nucleus of the hypothalamus/arcuate nucleus (VMH/ARC) and the lateral hypothalamus. In intact females, consumption of HFD increased prepro-QRFP and QRFP-r1 mRNA levels in the VMH/ARC during diestrus, a phase associated with increased food intake and low levels of E2. To assess the effects of diminished endogenous E2, rats were ovariectomized. HFD consumption and OVX increased prepro-QRFP mRNA in the VMH/ARC. Ovariectomized rats consuming HFD expressed the highest levels of QRFP. In the third experiment, all rats received EB replacement every 4days following OVX to examine the effects of E2 on QRFP expression. Prepro-QRFP, QRFP-r1 and QRFP-r2 mRNA were assessed prior to and following EB administration. EB replacement significantly reduced prepro-QRFP mRNA expression in the VMH/ARC. Overall these studies support a role for E2 in the regulation of prepro-QRFP mRNA in the VMH/ARC and suggest that E2's effects on food intake may be via a direct effect on the orexigenic peptide, QRFP.

Kisspeptin Regulation of Neuronal Activity throughout the Central Nervous System

Kisspeptin signaling at the gonadotropin-releasing hormone (GnRH) neuron is now relatively well characterized and established as being critical for the neural control of fertility. However, kisspeptin fibers and the kisspeptin receptor (KISS1R) are detected throughout the brain suggesting that kisspeptin is involved in regulating the activity of multiple neuronal circuits. We provide here a review of kisspeptin actions on neuronal populations throughout the brain including the magnocellular oxytocin and vasopressin neurons, and cells within the arcuate nucleus, hippocampus, and amygdala. The actions of kisspeptin in these brain regions are compared to its effects upon GnRH neurons. Two major themes arise from this analysis. First, it is apparent that kisspeptin signaling through KISS1R at the GnRH neuron is a unique, extremely potent form or neurotransmission whereas kisspeptin actions through KISS1R in other brain regions exhibit neuromodulatory actions typical of other neuropeptides. Second, it is becoming increasingly likely that kisspeptin acts as a neuromodulator not only through KISS1R but also through other RFamide receptors such as the neuropeptide FF receptors (NPFFRs). We suggest likely locations of kisspeptin signaling through NPFFRs but note that only limited tools are presently available for examining kisspeptin cross-signaling within the RFamide family of neuropeptides.

RF-amide neuropeptides and their receptors in Mammals: Pharmacological properties, drug development and main physiological functions

RF-amide neuropeptides, with their typical Arg-Phe-NH2 signature at their carboxyl C-termini, belong to a lineage of peptides that spans almost the entire life tree. Throughout evolution, RF-amide peptides and their receptors preserved fundamental roles in reproduction and feeding, both in Vertebrates and Invertebrates. The scope of this review is to summarize the current knowledge on the RF-amide systems in Mammals from historical aspects to therapeutic opportunities. Taking advantage of the most recent findings in the field, special focus will be given on molecular and pharmacological properties of RF-amide peptides and their receptors as well as on their implication in the control of different physiological functions including feeding, reproduction and pain. Recent progress on the development of drugs that target RF-amide receptors will also be addressed.

The Role of Arginine-Phenylalanine-Amide-Related Peptides in Mammalian Reproduction

Until 2000 it was believed that gonadotropin-releasing hormone (GnRH) was the sole regulator of hypophyseal gonadotropes. In 2000, the discovery of a gonadotropin inhibitory hormone (GnIH) initiated a revolution in the field of reproductive physiology. Identification of GnIH homologues in mammals, the arginine-phenylalanine-amide (RFamide)-related peptides (RFRPs), indicated a similar function. Subsequently, further works conducted in various laboratories worldwide have shown that these neuropeptides inhibit the hypothalamic-hypophyseal axis. This review discusses the role of RFRPs in mammalian reproductive processes.

Effects of direct QRFP-26 administration into the medial hypothalamic area on food intake in rats

The RFamide peptide family comprises a number of biologically active peptides sharing RF motif at their C-terminal end. These peptides are involved in the control of multiple physiological functions including regulation of metabolism and feeding behavior. QRFP-43 as well as its 26-aminoacid residue QRFP-26 are able to cause orexigenic effect when administered to the rodents' cerebral ventricles. QRFPs have been suggested as the endogenous ligands of the previously orphan GPR103 receptors. GPR103 receptors share amino acid identity with other receptors of neuropeptides involved in feeding (NPY, NPFF, galanin). QRFP-26 expressing neurons and binding sites are densely present in the rat medial hypothalamus (MHA), an area directly responsible for the regulation of feeding. QRFP-26 was delivered to the target area by direct intrahypothalamic microinjection, and the consumption of liquid food was measured over a 60 min period. Both doses (100 and 200 ng) significantly increased food intake. Non-specific receptor antagonist BIBP3226 eliminated the orexigenic effect caused by QRFP-26 administration. Effective doses of QRFP-26 did not modify general locomotor activity and behavioral patterns examined in the open-field test. This study is the first reporting feeding modulating effects following direct intrahypothalamic QRFP-26 administration.

The effect of kisspeptin on the regulation of vascular tone

Kisspeptin has been implicated in cardiovascular control. Eicosanoids play a crucial role in the activation of platelets and the regulation of vascular tone. In the present study, we investigated the effect of kisspeptins on eicosanoid synthesis in platelets and aorta in vitro. Platelets and aorta were isolated from Wistar–Kyoto rats. After preincubation with different doses of kisspeptin, samples were incubated with [1-14C]arachidonic acid (0.172 pmol/mL) in tissue culture Medium 199. The amount of labeled eicosanoids was measured with liquid scintillation, after separation with overpressure thin-layer chromatography. Kisspeptin-13 stimulated the thromboxane synthesis. The dose–response curve was bell-shaped and the most effective concentration was 2.5 × 10−8 mol/L, inducing a 27% increase. Lipoxygenase products of platelets displayed a dose-dependent elevation up to the dose of 5 × 10−8 mol/L. In the aorta, kisspeptin-13 induced a marked elevation in the production of 6-keto-prostaglandin F1α, the stable metabolite of prostacyclin, and lipoxygenase products. Different effects of kisspeptin on cyclooxygenase and lipoxygenase products indicate that beyond intracellular Ca2+ mobilization, other signaling pathways might also contribute to its actions. Our data suggest that kisspeptin, through the alteration of eicosanoid synthesis in platelets and aorta, may play a physiologic and (or) pathologic role in the regulation of vascular tone.

QRFP-26 enhances insulin's effects on glucose uptake in rat skeletal muscle cells

QRFP is expressed in central and peripheral regions important for nutrient intake and metabolism. Central administration of QRFP-26 and QRFP-43 induces a macronutrient specific increase in the intake of high fat diet in male and female rats. Recently, cell culture models have indicated that QRFP-26 and QRFP-43 are involved in glucose and fatty acid uptake in pancreatic islets and adipocytes. Since skeletal muscle is a major consumer of circulating glucose and a primary contributor to whole body metabolism, the current study examined the effects of QRFP-26 and QRFP-43 on insulin-stimulated uptake of glucose in skeletal muscle using L6 myotubes. The current experiments were designed to test the hypothesis that QRFP and its receptors, GPR103a and GPR103b are expressed in L6 myotubes and that QRFP-26 and QRFP-43 affect insulin-stimulated uptake of glucose in L6 myotubes. The results indicate that prepro-QRFP mRNA and GPR103a mRNA are expressed in L6 cells, though GPR103b mRNA was not detected. Using complementary assays, co-incubation with QRFP-26, increased insulin's ability to induce glycogen synthesis and 2-deoxyglucose uptake in L6 cells. These data suggest that QRFP-26, but not QRFP-43, is involved in the metabolic effects of skeletal muscle and may enhance insulin's effects on glucose uptake in skeletal muscle. These data support a role for QRFP as a modulator of nutrient intake in skeletal muscle.

Kisspeptin-13 enhances memory and mitigates memory impairment induced by Aβ1-42 in mice novel object and object location recognition tasks

Kisspeptin (KP), the endogenous ligand of GPR54, is a recently discovered neuropeptide shown to be involved in regulating reproductive system, anxiety-related behavior, locomotion, food intake, and suppression of metastasis across a range of cancers. KP is transcribed within the hippocampus, and GPR54 has been found in the amygdala and hippocampus, suggesting that KP might be involved in mediating learning and memory. However, the role of KP in cognition was largely unclear. Here, we investigated the role of KP-13, one of the endogenous active isoforms, in memory processes, and determined whether KP-13 could mitigate memory impairment induced by Aβ1-42 in mice, using novel object recognition (NOR) and object location recognition (OLR) tasks. Intracerebroventricular (i.c.v.) infusion of KP-13 (2μg) immediately after training not only facilitated memory formation, but also prolonged memory retention in both tasks. The memory-improving effects of KP-13 could be blocked by the GPR54 receptor antagonist, kisspeptin-234 (234), and GnRH receptors antagonist, Cetrorelix, suggesting pharmacological specificity. Then the memory-enhancing effects were also presented after infusion of KP-13 into the hippocampus. Moreover, we found that i.c.v. injection of KP-13 was able to reverse the memory impairment induced by Aβ1-42, which was inhibited by 234. To sum up, the results of our work indicate that KP-13 could facilitate memory formation and prolong memory retention through activation of the GPR54 and GnRH receptors, and suppress memory-impairing effect of Aβ1-42 through activation of the GPR54, suggesting that KP-13 may be a potential drug for enhancing memory and treating Alzheimer's disease.

Identification of G Protein-Coupled Receptors (GPCRs) in Primary Cilia and Their Possible Involvement in Body Weight Control

Primary cilia are sensory organelles that harbor various receptors such as G protein-coupled receptors (GPCRs). We analyzed subcellular localization of 138 non-odorant GPCRs. We transfected GPCR expression vectors into NIH3T3 cells, induced ciliogenesis by serum starvation, and observed subcellular localization of GPCRs by immunofluorescent staining. We found that several GPCRs whose ligands are involved in feeding behavior, including prolactin-releasing hormone receptor (PRLHR), neuropeptide FF receptor 1 (NPFFR1), and neuromedin U receptor 1 (NMUR1), localized to the primary cilia. In addition, we found that a short form of dopamine receptor D2 (DRD2S) is efficiently transported to the primary cilia, while a long form of dopamine receptor D2 (DRD2L) is rarely transported to the primary cilia. Using an anti-Prlhr antibody, we found that Prlhr localized to the cilia on the surface of the third ventricle in the vicinity of the hypothalamic periventricular nucleus. We generated the Npy2r-Cre transgenic mouse line in which Cre-recombinase is expressed under the control of the promoter of Npy2r encoding a ciliary GPCR. By mating Npy2r-Cre mice with Ift80 flox mice, we generated Ift80 conditional knockout (CKO) mice in which Npy2r-positive cilia were diminished in number. We found that Ift80 CKO mice exhibited a body weight increase. Our results suggest that Npy2r-positive cilia are important for body weight control.

Kisspeptin regulation of arcuate neuron excitability in kisspeptin receptor knockout mice

The G protein-coupled receptor 54 (GPR54) is critical for kisspeptin to activate GnRH neurons to modulate fertility. However, the often mismatching distribution of kisspeptin and GPR54 in the brain suggests that kisspeptin may also act on other receptors. The arcuate nucleus (ARN) is one brain region with a very high density of kisspeptin fibers but only limited evidence for the expression of GPR54. Using acute brain slice electrophysiology in combination with Gpr54 knockout (GPR54KO) mouse models, we examined whether actions of kisspeptin in the ARN were dependent upon GPR54. Cell-attached recordings from unidentified ARN neurons in wild-type mice revealed that approximately one third of neurons were either excited or inhibited by kisspeptin in a dose-dependent manner. The responses of ARN neurons to kisspeptin were exactly the same in GPR54KO mice despite effects of kisspeptin on GnRH neurons being abolished. To evaluate whether kisspeptin may be acting through neuropeptide FF receptors, the effects of an agonist RFamide-related peptide 3 (RFRP-3) and antagonists RF9 and BIBP-3226 were evaluated. Both the excitatory and inhibitory effects of kisspeptin were mimicked by the agonist RFRP-3. RF9 itself activated ARN neurons and suppressed only the inhibitory actions of kisspeptin. BIBP-3226 suppressed kisspeptin actions in 50% of neurons. Whole-cell recordings in GPR54KO mice demonstrated that both kisspeptin and RFRP-3 acted directly on the same ARN neurons and activated the same ion channels. Together, these studies demonstrate that kisspeptin can act partly through neuropeptide FF receptors to modulate neuronal activity independent of GPR54 in the mouse brain.

Dissecting the Roles of Gonadotropin-Inhibitory Hormone in Mammals: Studies Using Pharmacological Tools and Genetically Modified Mouse Models

Reproduction is essential for perpetuation of the species and, hence, is controlled by a sophisticated network of regulatory factors of central and peripheral origin that integrate at the hypothalamic-pituitary-gonadal (HPG) axis. Among the central regulators of reproduction, kisspeptins, as major stimulatory drivers of gonadotropin-releasing hormone (GnRH) neurosecretion, have drawn considerable interest in the last decade. However, the dynamic, if not cyclic (in the female), nature of reproductive function and the potency of kisspeptins and other stimulatory signals of the HPG axis make tenable the existence of counterbalance inhibitory mechanisms, which may keep stimulation at check and would allow adaptation of reproductive maturation and function to different endogenous and environmental conditions. In this context, discovery of the gonadotropin-inhibitory hormone (GnIH) in birds, and its mammalian homolog, RFRP, opened up the exciting possibility that this inhibitory signal might operate centrally to suppress, directly or indirectly, GnRH/gonadotropin secretion, thus reciprocally cooperating with other stimulatory inputs in the dynamic regulation of the reproductive hypothalamic-pituitary unit. After more than 15 years of active research, the role of GnIH/RFRP in the control of the HPG axis has been documented in different species. Yet, important aspects of the physiology of this system, especially regarding its relative importance and actual roles in the control of key facets of reproductive function, remain controversial. In the present work, we aim to provide a critical review of recent developments in this area, with special attention to studies in rodent models, using pharmacological tools and functional genomics. In doing so, we intend to endow the reader with an updated view of what is known (and what is not known) about the physiological role of GnIH/RFRP signaling in the control of mammalian reproduction.

Contribution of GnIH Research to the Progress of Reproductive Neuroendocrinology

Since the discovery of gonadotropin-releasing hormone (GnRH) in mammals at the beginning of the 1970s, it was generally accepted that GnRH is the only hypothalamic neuropeptide regulating gonadotropin release in mammals and other vertebrates. In 2000, however, gonadotropin-inhibitory hormone (GnIH), a novel hypothalamic neuropeptide that actively inhibits gonadotropin release, was discovered in quail. Numerous studies over the past decade and a half have demonstrated that GnIH serves as a key player regulating reproduction across vertebrates, acting on the brain and pituitary to modulate reproductive physiology and behavior. In the latter case, recent evidence indicates that GnIH can regulate reproductive behavior through changes in neurosteroid, such as neuroestrogen, biosynthesis in the brain. This review summarizes the discovery of GnIH, and the contributions to GnIH research focused on its mode of action, regulation of biosynthesis, and how these findings advance our understanding of reproductive neuroendocrinology.

Epigenetic regulation of female puberty

Substantial progress has been made in recent years toward deciphering the molecular and genetic underpinnings of the pubertal process. The availability of powerful new methods to interrogate the human genome has led to the identification of genes that are essential for puberty to occur. Evidence has also emerged suggesting that the initiation of puberty requires the coordinated activity of gene sets organized into functional networks. At a cellular level, it is currently thought that loss of transsynaptic inhibition, accompanied by an increase in excitatory inputs, results in the pubertal activation of GnRH release. This concept notwithstanding, a mechanism of epigenetic repression targeting genes required for the pubertal activation of GnRH neurons was recently identified as a core component of the molecular machinery underlying the central restraint of puberty. In this chapter we will discuss the potential contribution of various mechanisms of epigenetic regulation to the hypothalamic control of female puberty.

Characterization of peptide QRFP (26RFa) and its receptor from amphioxus, Branchiostoma floridae

A peptide ending with RFamide (Arg-Phe-amide) was discovered independently by three different laboratories in 2003 and named 26RFa or QRFP. In mammals, a longer version of the peptide, 43 amino acids, was identified and found to bind to the orphan G protein-coupled receptor GPR103. We searched the genome database of Branchiostoma floridae (Bfl) for receptor sequences related to those that bind peptides ending with RFa or RYa (including receptors for NPFF, PRLH, GnIH, and NPY). One receptor clustered in phylogenetic analyses with mammalian QRFP receptors. The gene has 3 introns in Bfl and 5 in human, but all intron positions differ, implying that the introns were inserted independently. A QRFP-like peptide consisting of 25 amino acids and ending with RFa was identified in the amphioxus genome. Eight of the ten last amino acids are identical between Bfl and human. The prepro-QRFP gene in Bfl has one intron in the propeptide whereas the human gene lacks introns. The Bfl QRFP peptide was synthesized and the receptor was functionally expressed in human cells. The response was measured as inositol phosphate (IP) turnover. The Bfl QRFP peptide was found to potently stimulate the receptor's ability to induce IP turnover with an EC50 of 0.28nM. Also the human QRFP peptides with 26 and 43 amino acids were found to stimulate the receptor (1.9 and 5.1nM, respectively). Human QRFP with 26 amino acids without the carboxyterminal amide had dramatically lower potency at 1.3μM. Thus, we have identified an amphioxus QRFP-related peptide and a corresponding receptor and shown that they interact to give a functional response.

Expression profile of neurotransmitter receptor and regulatory genes in the prefrontal cortex of spontaneously hypertensive rats: relevance to neuropsychiatric disorders

The spontaneously hypertensive rat (SHR) strain was shown to be a useful animal model to study several behavioral, pathophysiological and pharmacological aspects of schizophrenia and attention-deficit/hyperactivity disorder. To further understand the genetic underpinnings of this model, our primary goal in this study was to compare the gene expression profile of neurotransmitter receptors and regulators in the prefrontal cortex (PFC) and nucleus accumbens (NAcc) of SHR and Wistar rats (control group). In addition, we investigated DNA methylation pattern of promoter region of the genes differentially expressed. We performed gene expression analysis using a PCRarray technology, which simultaneously measures the expression of 84 genes related to neurotransmission. Four genes were significantly downregulated in the PFC of SHR compared to Wistar rats (Gad2, Chrnb4, Slc5a7, and Qrfpr) and none in nucleus accumbens. Gad2 and Qrfpr have CpG islands in their promoter region. For both, the promoter region was hypomethylated in SHR group, and probably this mechanism is not related with the downregulation of these genes. In summary, we identified genes that are downregulated in the PFC of SHR, and might be related to the behavioral abnormalities exhibited by this strain.

Mutational analysis of the genes encoding RFamide-related peptide-3, the human orthologue of gonadotrophin-inhibitory hormone, and its receptor (GPR147) in patients with gonadotrophin-releasing hormone-dependent pubertal disorders

RFamide-related peptide-3 (RFRP-3), the orthologue of avian gonadotrophin-inhibitory hormone, and its receptor GPR147 have been recently identified in the human hypothalamus, and their roles in the regulation of reproductive axis has been studied. The present study aimed to investigate whether the presence of variants in the genes encoding human RFRP-3 (NPVF gene) and its receptor, GPR147 (NPFFR1 gene), is associated with the occurrence of gonadotrophin-releasing hormone-dependent pubertal disorders. Seventy-eight patients with idiopathic central precocious puberty (CPP) and 51 with normosmic isolated hypogonadotrophic hypogonadism (nIHH) were investigated. Fifty healthy subjects comprised the control group. The coding sequences of the NPVF and NPFFR1 genes were amplified and sequenced. Odds ratios (OR) were used to estimate the likelihood of CPP or nIHH in the presence of the described polymorphisms. All such polymorphisms have already been registered in the National Center for Biotechnology Information database. A three-nucleotide in frame deletion was identified in the NPVF gene (p.I71_K72), with a smaller proportion in the CPP (5%) compared to the nIHH (15%) group (P = 0.06). This results in the deletion of the isoleucine at position 71, adjacent to lysine at an endoproteolytic cleavage site of the precursor peptide. This polymorphism was associated with a lower risk of CPP (OR = 0.33; 95% confidence interval = 0.08-0.88); interestingly, only two men with nIHH were homozygotes for this variant. A total of five missense polymorphisms were found in the NPFFR1 gene, which encodes GPR147, with similar frequencies among groups and no association with pubertal timing. Our data suggest that RFRP-3/GPR147 may play secondary, modulatory roles on the regulation of pubertal development; a restraining modulatory effect of the NPVF p.I71_K72 variant on the activation of the gonadotrophic axis cannot be ruled out and deserves further investigation.

LPXRFa, the piscine ortholog of GnIH, and LPXRF receptor positively regulate gonadotropin secretion in Tilapia (Oreochromis niloticus)

LPXRFamide (LPXRFa) peptides have been characterized for their ability to inhibit gonadotropin (GTH) release in birds and stimulate growth hormone (GH) release in frogs. However, their involvement in regulating the reproductive hypothalamo-pituitary-gonadal axis in mammals and fish is inconclusive. To study the role of LPXRFa peptides in the regulation of GTH secretion, we cloned tilapia LPXRFa and LPXRF receptor (LPXRF-R). Processing of the tilapia preproLPXRFa liberated three mature LPXRFa peptides that varied in size and post-translational modifications. Phylogenetic analysis of LPXRFa and the closely related RFamide peptide PQRFa showed clear clustering of each peptide sequence with its orthologs from various vertebrates. Signal-transduction analysis of the tilapia LPXRF-R in COS-7 cells showed clear stimulation of CRE-dependent luciferase activity, whereas the human NPFFR1 showed suppression of forskolin-induced CRE-dependent activity in this system. Administration of the tilapia pyroglutaminated LPXRFa-2 peptide to primary cell culture of tilapia pituitaries, or to reproductive female tilapia by ip injection, positively regulated both LH and FSH release in vivo and in vitro. Using double-labeled fluorescent in-situ hybridization and immunofluorescence, βLH cells were found to co-express both tilapia lpxrf and tilapia lpxrf-r mRNA, whereas some of the βFSH cells coexpressed only lpxrf-r mRNA. No coexpression of tilapia lpxrf-r was identified in GH-positive cells. These findings suggest that the LPXRFa system is a potent positive regulator of the reproductive neuroendocrine axis of tilapia.

Unexpected multiplicity of QRFP receptors in early vertebrate evolution

The neuropeptide QRFP, also called 26RFa, and its G protein-coupled receptor GPR103 have been identified in all vertebrates investigated. In mammals, this peptide-receptor pair has been found to have several effects including stimulation of appetite. Recently, we reported that a QRFP peptide is present in amphioxus, Branchiostoma floridae, and we also identified a QRFP receptor (QRFPR) that mediates a functional response to sub-nanomolar concentrations of the amphioxus peptide as well as short and long human QRFP (Xu et al., submitted). Because the ancestral vertebrate underwent two tetraploidizations, it might be expected that duplicates of the QRFP gene and its receptor gene may exist. Indeed, we report here the identification of multiple vertebrate QRFPR genes. Three QRFPR genes are present in the coelacanth Latimeria chalumnae, representing an early diverging sarcopterygian lineage. Three QRFPR genes are present in the basal actinopterygian fish, the spotted gar. Phylogenetic and chromosomal analyses show that only two of these receptor genes are orthologous between the two species, thus demonstrating a total of four distinct vertebrate genes. Three of the QRFPR genes resulted from the early vertebrate tetraploidizations and were copied along with syntenic neuropeptide Y receptor genes. The fourth QRFPR gene may be an even older and distinct lineage. Because mammals and birds have only a single QRFPR gene, this means that three genes have been lost in these lineages, and at least one of these was lost independently in mammals and birds because it is still present in a turtle. In conclusion, these results show that the QRFP system gained considerable complexity in the early stages of vertebrate evolution and still maintains much of this in some lineages, and that it has been secondarily reduced in mammals.