Phylogenetic study of the arginine-vasotocin/arginine-vasopressin-like immunoreactive system in invertebrates

Comparative and Evolutionary Physiology of Vasopressin/ Oxytocin-Type Neuropeptide Signaling in Invertebrates

The identification of structurally related hypothalamic hormones that regulate blood pressure and diuresis (vasopressin, VP; CYFQNCPRG-NH2) or lactation and uterine contraction (oxytocin, OT; CYIQNCPLG-NH2) was a major advance in neuroendocrinology, recognized in the award of the Nobel Prize for Chemistry in 1955. Furthermore, the discovery of central actions of VP and OT as regulators of reproductive and social behavior in humans and other mammals has broadened interest in these neuropeptides beyond physiology into psychology. VP/OT-type neuropeptides and their G-protein coupled receptors originated in a common ancestor of the Bilateria (Urbilateria), with invertebrates typically having a single VP/OT-type neuropeptide and cognate receptor. Gene/genome duplications followed by gene loss gave rise to variety in the number of VP/OT-type neuropeptides and receptors in different vertebrate lineages. Recent advances in comparative transcriptomics/genomics have enabled discovery of VP/OT-type neuropeptides in an ever-growing diversity of invertebrate taxa, providing new opportunities to gain insights into the evolution of VP/OT-type neuropeptide function in the Bilateria. Here we review the comparative physiology of VP/OT-type neuropeptides in invertebrates, with roles in regulation of reproduction, feeding, and water/salt homeostasis emerging as common themes. For example, we highlight recent reports of roles in regulation of oocyte maturation in the sea-squirt Ciona intestinalis, extraoral feeding behavior in the starfish Asterias rubens and energy status and dessication resistance in ants. Thus, VP/OT-type neuropeptides are pleiotropic regulators of physiological processes, with evolutionarily conserved roles that can be traced back to Urbilateria. To gain a deeper understanding of the evolution of VP/OT-type neuropeptide function it may be necessary to not only determine the actions of the peptides but also to characterize the transcriptomic/proteomic/metabolomic profiles of cells expressing VP/OT-type precursors and/or VP/OT-type receptors within the framework of anatomically and functionally identified neuronal networks. Furthermore, investigation of VP/OT-type neuropeptide function in a wider range of invertebrate species is now needed if we are to determine how and when this ancient signaling system was recruited to regulate diverse physiological and behavioral processes in different branches of animal phylogeny and in contrasting environmental contexts.

Role of Oxytocin/Vasopressin-Like Peptide and Its Receptor in Vitellogenesis of Mud Crab

Oxytocin (OT)/vasopressin (VP) signaling system is important to the regulation of metabolism, osmoregulation, social behaviours, learning, and memory, while the regulatory mechanism on ovarian development is still unclear in invertebrates. In this study, Spot/vp-like and its receptor (Spot/vpr-like) were identified in the mud crab Scylla paramamosain. Spot/vp-like transcripts were mainly expressed in the nervous tissues, midgut, gill, hepatopancreas, and ovary, while Spot/vpr-like were widespread in various tissues including the hepatopancreas, ovary, and hemocytes. In situ hybridisation revealed that Spot/vp-like mRNA was mainly detected in 6–9th clusters in the cerebral ganglion, and oocytes and follicular cells in the ovary, while Spot/vpr-like was found to localise in F-cells in the hepatopancreas and oocytes in the ovary. In vitro experiment showed that the mRNA expression level of Spvg in the hepatopancreas, Spvgr in the ovary, and 17β-estradiol (E₂) content in culture medium were significantly declined with the administration of synthetic SpOT/VP-like peptide. Besides, after the injection of SpOT/VP-like peptide, it led to the significantly reduced expression of Spvg in the hepatopancreas and subduced E₂ content in the haemolymph in the crabs. In brief, SpOT/VP signaling system might inhibit vitellogenesis through neuroendocrine and autocrine/paracrine modes, which may be realised by inhibiting the release of E₂.

How evolutionary psychiatry can advance psychopharmacology

The prevailing paradigm for psychopharmacology focuses on understanding brain mechanisms as the key to finding new medications and improving clinical outcomes, but frustration with slow progress has inspired many pleas for new approaches. Evolutionary psychiatry brings in an additional basic science that poses new questions about why natural selection left us vulnerable to so many mental disorders, and new insights about how drugs work. The integration of neuroscience with evolutionary psychiatry is synergistic, going beyond reductionism to provide a model like the one used by the rest of medicine. It recognizes negative emotions as symptoms, that are, like pain and cough, useful defenses whose presence should initiate a search for causes. An integrative evolutionary approach explains why agents that block useful aversive responses are usually safe, and how to anticipate when they may cause harm. More generally, an evolutionary framework suggests novel practical strategies for finding and testing new drugs.


Molecular cloning and distribution of oxytocin/vasopressin-like mRNA in the blue swimming crab, Portunus pelagicus, and its inhibitory effect on ovarian steroid release

This study was aimed to characterize the full length of mRNA of oxytocin/vasopressin (OT/VP)-like mRNA in female Portunus pelagicus (PpelOT/VP-like mRNA) using a partial PpelOT/VP-like sequence obtained previously in our transcriptome analysis (Saetan, 2014) to construct the primers. The PpelOT/VP-like mRNA was 626 bp long and it encoded the preprohormones containing 158 amino acids. This preprohormone consisted of a signal peptide, an active nonapeptide (CFITNCPPG) followed by the dibasic cleavage site (GKR), and the neurophysin domain. Sequence alignment of the PpelOT/VP-like peptide with those of other animals revealed strong molecular conservation. Phylogenetic analysis of encoded proteins revealed that the PpelOT/VP-like peptide was clustered within the group of crustacean OT/VP-like peptide. Analysis by RT-PCR revealed the expression of mRNA transcripts in the eyestalk, brain, ventral nerve cord (VNC), ovary, intestine and gill. The in situ hybridization demonstrated the cellular localizations of the transcripts in the central nervous system (CNS) and ovary tissues. In the eyestalk, the mRNA expression was observed in the neuronal clusters 1-5 but not in the sinus gland complex. In the brain and the VNC, the transcripts were detected in all neuronal clusters but not in the glial cell. In the ovary, the transcripts were found in all stages of oocytes (Oc1, Oc2, Oc3, and Oc4). In addition, synthetic PpelOT/VP-like peptide could inhibit steroid release from the ovary. The knowledge gained from this study will provide more understanding on neuro-endocrinological controls in this crab species.

Vasopressin: a novel target for the prevention and retardation of kidney disease?

After several decades during which little attention was paid to vasopressin and/or urine concentration in clinical practice, interest in vasopressin has renewed with the availability of new, potent, orally active vasopressin-receptor antagonists--the vaptans--and with the results of epidemiological studies evaluating copeptin (a surrogate marker of vasopressin) in large population-based cohorts. Several experimental studies in rats and mice had previously shown that vasopressin, acting via vasopressin V2 antidiuretic receptors, contributes to the progression of chronic kidney disease; in particular, to autosomal dominant polycystic kidney disease. New epidemiological studies now suggest a role for vasopressin in the pathogenesis of diabetes mellitus and metabolic disorders via activation of hepatic V1a and/or pancreatic islet V1b receptors. The first part of this Review describes the adverse effects of vasopressin, as revealed by clinical and experimental studies in kidney diseases, hypertension, diabetes and the metabolic syndrome. The second part provides insights into vasopressin physiology and pathophysiology that may be relevant to the understanding of these adverse effects and that are linked to the excretion of concentrated nitrogen wastes and associated hyperfiltration. Collectively, the studies reviewed here suggest that more attention should be given to the vasopressin-thirst-urine concentration axis in clinical investigations and in patient care. Whether selective blockade of the different vasopressin receptors may provide therapeutic benefits beyond their present indication in hyponatraemia requires new clinical trials.

Identification of a vasopressin-like immunoreactive substance in hydra

Vasopressin (VP)-like immunoreactivity has long been known in the hydra nervous system, but has not yet been structurally identified. In this study, using HPLC fractionation and an immunological assay, we have purified two peptides, FPQSFLPRGamide and SFLPRGamide, from Hydra magnipapillata. Both the peptides shared the same C-terminal structure, -PRGamide, with Arg-VP. The nonapeptide proved to be Hym-355, a peptide that stimulates neuronal differentiation in hydra. Detailed evaluation by competitive enzyme-linked immunosorbent assay (ELISA) and double immunostaining using anti-VP and anti-Hym-355 antibodies enabled us to conclude that the two peptides account for a major part of the VP-like immunoreactivity in hydra nerve cells.

Neuropeptide families: evolutionary perspectives

Examination of neuropeptide families can provide information about phyletic relationships and evolutionary processes. In this article the oxytocin/vasopressin family, growth hormone releasing factor (GRF) superfamily and the substance P/tachykinin family have been considered in detail because they have been isolated from an extraordinarily diverse array of species from several vertebrate classes and invertebrate phyla. More important is that the nucleotide sequence of mRNA or cDNA encoding many of these peptides has been determined, which has allowed evolutionary distances to be estimated based on the DNA mutation rate. The origin of a given family lies in a primordial gene that arose many millions of years ago, and through time, exon duplication and insertion, gene duplication, point mutation and exon loss, the family developed into the forms that are now recognised. For example, in birds, GRF and pituitary adenylate cyclase activating peptide (PACAP) are encoded by the same gene, which probably arose as a result of exon duplication and tandem insertion of the ancestral GRF gene. In mammals GRF is the sole product on one gene, and PACAP is the product of a gene that also produces PACAP-related peptide (PRP), which is homologous to GRF. Thus it appears that between birds and mammals the GRF/PACAP gene duplicated: exon loss gave rise to the mammalian GRF gene, while mutation led to the formation of the mammalian PRP/PACAP gene. The neuropeptide Y superfamily is considered briefly, as is cionin, which is an invertebrate peptide that is closely related to the mammalian gastrin/cholecystokinin family.

Isolation, structural characterization and biological function of a lysine-conopressin in the central nervous system of the pharyngobdellid leech Erpobdella octoculata

Several neuropeptides are suspected to act on the control of hydric balance in leeches. One of these peptides, a peptide immunoreactive to an antibody against oxytocin, was previously characterized from the central nervous system of the leech Erpobdella octoculata [Salzet, M., Wattez, C., Verger-Bocquet, M., Beauvillain, J.-C. & Malecha, J. (1993) Brain Res. 601, 173-184]. This paper reports the isolation from the central nervous system of E. octoculata of another peptide of the oxytocin/vasopressin family; a lysine-vasopressin-like molecule. Its purification was performed by reverse-phase high-performance liquid chromatography combined with both dot immunobinding assay and enzyme-linked immunosorbent assay for lysine-vasopressin. The amino acid sequence was established by Edman degradation and confirmed by electrospray-mass-spectrometry measurement. The nonapeptide obtained corresponded to the lysine-conopressin previously isolated from the venom of the mollusc Conus geographus [Cruz, L. L., de Santos, V., Zafaralla, G. C., Ramilo, C. A., Zeikus, R., Gray, W. R. & Olivera, B. M. (1987) J. Biol. Chem. 262, 15821-15824]. In leeches, synthetic lysine-conopressin exerts a diuretic effect which can be compared to that of the arginine-vasopressin-like peptide isolated in the Insect Locusta migratoria [Proux, J., Miller, C. A., Li, J. P., Carney, R. L., Girardie, A., Delaage, M. & Schooley, D. A. (1987) Biochem. Biophys. Res. Commun. 149, 180-186].

Localization of vasopressin-like immunoreactivity in the CNS of Aplysia californica

Chromatographic and immunological evidence indicates that a vasopressin-like peptide might be present in the CNS of Aplysia californica, and that this peptide may be involved in modulating the behaviour of the gill. Immunocytochemical techniques using antisera raised against various vasopressin-like peptides were used to localize the sites containing these peptides in the CNS of Aplysia. Vasopressin-like immunoreactivity was found to be restricted to one single neuron in the abdominal ganglion and two small neurons located bilaterally in each pedal ganglion. Immunoreactive fibres were present in the neuropile of the abdominal, pedal, pleural and cerebral ganglia, but not in the buccal ganglion. The identification of these neurons provides a morphological localization for vasopressin-like substances detected previously in CNS extracts of Aplysia californica. In addition, the possibility of electrophysiological studies involving the immunoreactive neurons identified in the present paper will allow a more direct approach to study the physiological role of vasopressin-like peptides in Aplysia.

Vasopressin-immunoreactive neurons and neurohemal systems in cockroaches and mantids

Vasopressin-like neuropeptides of insects are of special interest because of their possible function as hormones and neuromodulators. Therefore, this study was undertaken by using whole-mount immunofluorescent staining by two antisera that recognize different types of vasopressin-like immunoreactive groups of neurons in the cockroaches Periplaneta americana, Leucophaea maderae, Nauphoeta cinerea, Diploptera punctata, and Blaberus discoidalis and in the mantids Litaneuria minor and Tenodera aridifolia sinensis. Using an antiserum to Arg/vasopressin, only two cells, the paired ventral paramedian (PVP) neurons, were immunostained in the central nervous system (CNS) of the cockroaches. These cells are located in the subesophageal ganglion, project throughout the CNS, and appear to be neurosecretory. Their varicose collaterals extend into the dorsal (motor) neuropil of the segmental ganglia, and this neuropil may be the principal site of the release of their neurosecretion. The PVP neurons were also stained by an antiserum to Lys/vasopressin; in addition, this antiserum stained several other groups of neurons, most of which appeared to be neurosecretory. Two pairs of Lys/vasopressin-immunoreactive cells are similar to the PVP neurons in that they are located in the subesophageal ganglion, extend through the ventral nerve cord, have collaterals in the dorsal neuropil of the segmental ganglia, and appear to be neurosecretory within the CNS. In addition, midventral and anteroventral clusters of Lys/vasopressin-immunoreactive neurosecretory neurons in the subesophageal ganglion project neurohemal release sites on the corpora allata. Other types of Lys/vasopressin-immunoreactive neurons include median and lateral neurosecretory cells of the protocerebrum and neurosecretory cells in the tritocerebrum, all of which project to the corpora cardiaca. In the abdominal ganglia there are posterolateral clusters of Lys/vasopressin neurosecretory neurons, and these cells extend to neurohemal release sites on the transverse and lateral cardiac nerves. In mantids the anti-Arg/vasopressin and anti-Lys/vasopressin antisera stained most of the same groups of neurons that these antisera recognized in cockroaches. The results of this study suggest that there are two or more vasopressin-like peptides in cockroaches and mantids and that these peptides may be released either as hormones in the blood or as neurosecretions within the CNS. Their function(s) in these insects remains to be determined.

A vasotocin-like peptide in Aplysia kurodai ganglia: HPLC and RIA evidence for its identity with Lys-conopressin G

The presence of a vasopressin (VP)- or vasotocin (VT)-like peptide in the central nervous system of the gastropod mollusc Aplysia has been indicated previously. In the case of Aplysia californica, HPLC and RIA evidence suggested the peptide was VT-like but not identical with the nonmammalian vertebrate peptide [Arg8]VT (AVT). In the present study, anterior ganglia extracts from the related species Aplysia kurodai were analyzed by HPLC followed by RIA. Further analysis of the major AVT-IR peak showed it to be indistinguishable, in three distinct solvent systems, from the sea snail venom peptide Lys-conopressin G, but to be different from the vertebrate peptides [Arg8]VP (AVP), [Lys8]VP (LVP), AVT, oxytocin (OT), mesotocin, isotocin, aspargtocin, glumitocin, and valitocin, from the sea snail venom peptide Arg-conopressin S, and from the peptides [Lys8]VT and [Gln8]OT. In addition, the carboxymethylated (CM) A. kurodai peptide had the same HPLC retention time as CM-Lys-conopressin G. The HPLC/RIA results suggest that (i) based on the properties of the solvent systems used, the A. kurodai peptide has two basic amino acids (like the conopressins but unlike the vertebrate peptides), and (ii) there is a high probability that the A. kurodai peptide is identical with Lys-conopressin G.

Phylogenetic study of the oxytocin-like immunoreactive system in invertebrates

1. A phylogenetic study of oxytocin (OXT)-like immunoreactive cells was performed by the PAP method in the central nervous system of invertebrates. 2. The immunoreactivity was detected in the nerve cells of Hydra magnipapillata of the Coelenterata; Neanthes japonica and Pheretima communissima of the Annelida; Oncidium verrucosum, Limax marginatus and Meretrix lamarckii of the Mollusca; and Baratha brassica of the Arthropoda. 3. No immunoreactive cells were found in Bipalium sp. of the Platyhelminthes; Pomacea canaliculata, Aplysia kurodai, Bradybaena similaris and Achatina fulica of the Mollusca; and Gnorimosphaeroma rayi, Procambarus clarkii, Hemigrapsus sanguineus, Helice tridens and Gryllus bimaculatus of the Arthropoda; Asterina pectinifera of the Echinodermata; and Halocynthia roretzi of the Protochordata. 4. These results demonstrate that an OXT-immunoreactive substance is widely present not only in vertebrates but also in invertebrates. 5. OXT seems to have been introduced into these invertebrates at an early stage of their phylogenetic history.