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PubMed1989

Control of gastrointestinal motility by peptides: old peptides, new tricks--new peptides, old tricks.

The discovery of new peptides that may or may not be members of existing peptide families is stimulating research in the field of gastrointestinal motility. Before their function in control of human motility can be predicted, both anatomic and functional pathways must be determined in a number of animal models. In many instances this has just begun. In other instances old concepts must be revised. This review examines the recent findings that motor actions attributable to VIP and by extension to its colocalized family member PHI may occur by turning off a tonic release that has held the muscle in a relaxed state. For the opioid family, some of the very complex actions are probably attributable to its action to inhibit the tonic release of VIP. For the tachykinin/neurokinin family, the focus is on the potential role as a sensory transmitter released antidromically from afferent capsaicin-sensitive nerve endings. In summarizing the actions of galanin, the reader is cautioned against any extrapolation to other species, because the actions and structure of the peptides have been found to be different in each species examined. CGRP, again a sensory transmitter found colocalized with substance P, tends to exert an opposite action on the smooth muscle from substance P (that of relaxation), and the interactions between these peptides may well prove to be important in gastrointestinal reflexes. The PP, PYY, and NPY family require much more study in gastrointestinal motor systems but appear to act as presynaptic inhibitory transmitters in a variety of local motor reflexes. One caveat from one who studies these systems is never to predict the action of a new or old peptide in your system of study, because the complexity of the system appears to determine the action expressed.

Animals↗
PubMedDate not supplied

Central nervous system effects of peptides, 1980-1985: a cross-listing of peptides and their central actions from the first six years of the journal Peptides.

A tabular synopsis is presented for articles concerned with the effects of peptides on the central nervous system that appeared in the journal Peptides from 1980-1985. A table arranged alphabetically by peptide and one arranged by effects, both listing routes of injection, species, direction of change, and qualifying notes, provides easy cross-referencing of peptides and their effects. Over 80 peptides and over 135 effects are listed. The list of peptides includes, but is not limited to: ACTH, angiotensin, bombesin, bradykinin, calcitonin, casomorphin, CCK, ceruletide, CGRP, CRF, dermorphin, DSIP, dynorphin, endorphins, enkephalins, GRF, gastrin, LHRH, litorin, metkephamid, MIF-l, motilin, MSH, NPY, NT, oxytocin, ranatensin, sauvagine, substances P and K, somatostatin, TRH, VIP, vasopressin, and vasotocin. The list of effects includes, but is not limited to: aggression, alcohol, analgesia, attention, avoidance, behavior, cardiovascular regulation, catalepsy, conditioned behavior, convulsions, dopamine binding and metabolism, discrimination, drinking, EEG, exploration, feeding, fever, gastric secretion, GI motility, grooming, learning, locomotor behavior, mating, memory, neuronal activity, open field, operant behavior, rearing, respiration, satiety, scratching, seizure, sleep, stereotypy, temperature, thermoregulation and tolerance.

Animals↗
PubMed1994

CNS effects of peptides: a cross-listing of peptides and their central actions published in the journal Peptides, 1986-1993.

The centrally mediated effects of peptides as published in the journal Peptides from 1986 to 1993 are tabulated in two ways. In one table, the peptides are listed alphabetically. In another table, the effects are arranged alphabetically. Most of the effects observed after administration of peptides are grouped, wherever possible, into categories such as cardiovascular and gastrointestinal. The species used in most cases has been rats; where other animals were used, the species is noted. The route of administration of peptides and source of information also are included in the tables, with a complete listing provided at the end. Many peptides have been shown to exert a large number of centrally mediated effects.

Central Nervous System↗
PubMed2004

Association of plasma atrial natriuretic peptide, N-terminal proatrial natriuretic peptide, and brain natriuretic peptide levels with coronary artery stenosis in patients with normal left ventricular systolic function.

PURPOSE: To examine whether coronary artery stenosis affects plasma levels of atrial natriuretic peptide (ANP), N-terminal proatrial natriuretic peptide (proANP), and brain natriuretic peptide (BNP) in patients with normal left ventricular systolic function. METHODS: We studied 104 consecutive patients with normal left ventricular function and suspected coronary artery stenosis. Plasma natriuretic peptide levels were measured by immunoradiometric assays. RESULTS: Plasma levels of ANP, N-terminal proANP, and BNP were higher in patients with (n = 65) than in those without (n = 39) coronary artery stenosis, whereas hemodynamic variables were similar. Patients who had coronary artery stenosis with only distal lesions (n = 36) had higher levels of all three natriuretic peptides than did patients with no coronary artery stenosis. N-terminal proANP levels were significantly higher in patients who had coronary artery stenosis with proximal lesions (n = 29) than in patients who had coronary artery stenosis with only distal lesions and those with no coronary artery stenosis. Multiple logistic regression analysis revealed that N-terminal proANP, but not ANP or BNP, was independently associated with coronary artery stenosis after adjusting for clinical and demographic variables (odds ratio per 100 fmol/mL increase = 1.9; 95% confidence interval: 1.9 to 2.6; P = 0.01). However, the sensitivity, specificity, and positive and negative predictive values of each peptide were not sufficiently high to be used for prediction. CONCLUSION: N-terminal proANP may be associated with clinically important coronary artery stenosis in patients with normal left ventricular systolic function, but its clinical usefulness may be limited.

Atrial Natriuretic Factor↗
PubMed2000

Partitioning of peptides and recombinant protein-peptide fusions in thermoseparating aqueous two-phase systems: effect of peptide primary structure.

Genetic engineering has been used for fusion of peptides, with different length and composition, on a protein to study the effect on partitioning in an aqueous two-phase system. The system was composed of dextran and the thermoseparating ethylene oxide-propylene oxide random copolymer, EO30P070. Peptides containing tryptophan, proline, arginine or aspartate residues were fused at the C-terminus of the recombinant protein ZZ-cutinase. The aim was to find effective tags for the lipolytic enzyme cutinase for large-scale extraction. The target protein and peptide tags were partitioned separately and then together in the fusion proteins in order to gain increased understanding of the influence of certain amino acid residues on the partitioning. The salt K2SO4 was used to reduce the charge dependent salt effects on partitioning and to evaluate the contribution to the partition coefficient from the hydrophobic-hydrophilic properties of the amino acid residues. The effect of Trp on peptide partitioning was independent of the difference in primary structure for (Trp)n, (Trp-Pro)n, (Ala-Trp-Trp-Pro)n and was only determined by the number of Trp. The effect of the charged residues, Arg and Asp, was dependent on the surrounding residues, i.e. if they were situated next to Trp or not. The partitioning behaviour observed for the peptides was qualitatively and in some cases also quantitatively the same as for the fusion proteins. The effect of the salts sodium perchlorate and triethylammonium phosphate on the partitioning was also studied. The salt effects observed for the peptides were qualitatively similar to the effects observed for the fusion proteins.

Amino Acid Sequence↗
PubMed1988

Development of a radioimmunoassay for plasma C-peptide in sheep: kinetics of C-peptide and effects of exogenous growth hormone and glucose on insulin and C-peptide.

An antiserum to purified bovine C-peptide was used to develop a sensitive radioimmunoassay for C-peptide in sheep. The assay was used to measure kinetics of C-peptide and insulin in non-pregnant and non-lactating sheep. Injected, purified C-peptide was distributed in pools comprising c. 11.4% of liveweight, the half time of C-peptide was estimated as 13.7 min and its clearance rate was c. 5 ml kg-1 min-1. In lactating ewes exogenous recombinant bovine growth hormone (rebGH) increased both plasma insulin and C-peptide as did glucose challenge given before and during administration of rebGH. Estimates of insulin secretion rate in lactating ewes were c. 7 x 10(-3) and 8.5 x 10(-3) nmol kg-1 min-1 before and after glucose challenge prior to injections of rebGH. After 4 days of injection of rebGH, corresponding values were c. 8 x 10(-3) and 10 x 10(-3) nmol min-1 kg-1.

Animals↗
PubMed1993

Disulfide linkage to polyacrylic resin for automated Fmoc peptide synthesis. Immunochemical applications of peptide resins and mercaptoamide peptides.

The use of disulfide bonds for peptide-resin linkage in solid-phase peptide synthesis was investigated using polyacrylic polymers (Expansin) and automated Fmoc methodology. The disulfide moiety was bound to the support either by coupling a protected bifunctional handle or by an original stepwise procedure. Among the three different disulfide handles that were investigated, only the aminoethyldithio-2-isobutyric acid (AEDI) handle was stable enough to achieve peptide synthesis. A series of peptides of up to 10-20 amino acids were prepared in this manner, in good yield and purity. Rapid and quantitative peptide release was obtained by reduction with equimolecular amounts of dithiothreitol at pH 9 or tris(2-carboxymethyl) phosphine at pH 4.5. This allowed direct and rapid coupling of the released cysteamide peptides to an activated protein carrier and the use of free or resin-bound forms of the antigen in immunoassays.

Acrylic Resins↗
PubMed1996

Amino acids and peptides. XXIX. Synthesis and antimetastatic effects of peptides and peptide-poly(ethylene glycol) hybrids related to the core sequence of the type III connecting segment domain of fibronectin.

Peptides (H-Glu-Ile-Leu-Asp-Val-NH2, H-Glu-Ile-Leu-Asp-Val-Pro-Ser-Thr-NH2, H-Arg-Glu-Asp-Val-NH2) and their poly(ethylene glycol) (PEG) hybrids related to the core sequence of the type III connecting segment domain of fibronectin A chain were prepared by the solution method or the solid phase method. Their inhibitory effects on the adhesion and migration of B16-BL6 melanoma cells to fibronectin were assessed in vitro, and their therapeutic potency against tumor metastasis were also examined. Anti-adhesive and anti-migrative effects of the synthetic fibronectin-related peptids were superior to those of their PEG hybrids, so we found that the in vitro bioactivity of peptides decreased by PEGylation. In the in vivo assay, we found that the synthetic peptides containing Glu-Ile-Leu-Asp-Val and Arg-Glu-Asp-Val sequences exhibited an inhibitory effect on the experimental metastasis of B16-BL6 melanoma. Of the synthetic peptides, H-Glu-Ile-Leu-Asp-Val-NH2 exhibited the most potent inhibitory effect. Hybrid formation of Arg-Glu-Asp-Val with poly(ethylene glycol) resulted in potentiation of the inhibitory effect of the parent peptides. A mixture composed of PEG hybrids of Glu-Ile-Leu-Asp-Val, Arg-Glu-Asp-Val and Tyr-Ile-Gly-Ser-Arg dramatically inhibited tumor metastasis.

Animals↗
PubMedDate not supplied

Cyclic AMP formation in chicken brain: effect of vasoactive intestinal peptide, peptide histidine-isoleucine (PHI), and some PHI-related peptides.

Vasoactive intestinal peptide (chicken form; chVIP), peptide histidine-isoleucine (porcine and rat forms; pPHI and rPHI), D-Phe(4) derivative of porcine PHI (D-Phe(4)-pPHI), peptide histidine-methionine (PHM; human PHI), and helodermin, were tested for their ability to stimulate cAMP production in [(3)H]adenine-prelabeled slices of chick cerebral cortex (CCx) and hypothalamus (HTh). The chVIP (0.1-3 microM) concentration-dependently and potently stimulated cAMP production in HTh and CCx; the responses observed after 3 microM of chVIP were comparable to those produced by 0.1 microM PACAP38. Helodermin (5 microM) moderately but significantly stimulated cAMP formation in both HTh and CCx, whereas pPHI, rPHI, PHM at 5 microM concentration only weakly affected cAMP production in CCx, and were inactive in HTh; D-Phe(4)-pPHI was inactive in both tissues. These data demonstrate that chVIP, PACAP, and to a lesser extent helodermin were capable of potently stimulating cAMP generation in the avian central nervous system. PHI-related peptides showed only weak or no activity, depending on the tissue.

Animals↗
PubMed2002

Allotopic antagonism of the non-peptide atrial natriuretic peptide (ANP) antagonist HS-142-1 on natriuretic peptide receptor NPR-A.

The microbial polysaccharide HS-142-1 has been documented as an antagonist of natriuretic peptides. It inhibits activation and peptide binding to both guanylate receptors natriuretic peptide receptor (NPR)-A and NPR-B, but has no effect on the non-cyclase receptor NPR-C. At first sight the effect of HS-142-1 on peptide binding appears to be surmountable, suggesting that it might be competitive despite its chemically divergent nature. We explored its mode of action on wild-type NPR-A (WT), on a disulphide-bridged constitutively active mutant (C423S) and on truncated mutants lacking either their cytoplasmic domain (DeltaKC) or both the cytoplasmic and the transmembrane domains (ECD). On the WT, HS-142-1 inhibited atrial natriuretic peptide (ANP) binding with a pK value of 6.51 +/- 0.07 (K(d)=0.31 microM). It displayed a similar effect on the C423S mutant (pK=6.31 +/- 0.11), indicating that its action might not be due to interference with receptor dimerization. HS-142-1 also inhibited ANP binding to DeltaKC with a pK of 7.05 +/- 0.05 (K(d)=0.089 microM), but it was inactive on ANP binding to ECD at a concentration of 10(-4) M, suggesting that the antagonism was not competitive at the peptide-binding site located on the ECD and that the transmembrane domain might be required. HS-142-1 also enhanced dissociation of NPR-A-bound (125)I-ANP in the presence of excess unlabelled ANP, implying an allotopic (allosteric) mode of action for the antagonist.

Allosteric Regulation↗
PubMed2001

Clonal expansion of freshly isolated CD4T cells by randomized peptides and identification of peptide ligands using combinatorial peptide libraries.

We synthesized Xn (n = 9 -- 19) peptides that consist of 9 to 19 residues with random sequences. X19 is considered to deliver antigenic stimuli to CD4 T cells, because: (a) X19 induces proliferation of peripheral blood mononuclear cells (PBMC), in the presence of IL-2, which is abrogated by monoclonal antibodies to class II HLA; (b) X19 + IL-2 induces proliferation of CD4 T cell clones of distinct specificities; and (c) T cell clones recognizing the same TCR ligands with distinct V beta usage are equally stimulated by X19 + IL-2. We next co-cultured single peripheral CD4 T cells with X19 and mitomycin-treated autologous PBMC. Indeed, single T cells of CD45RA(-) memory phenotype exhibited clonal expansion, with variable rates of proliferation, when IL-4, IL-7, IL-9, IL-15 and agonistic antibody to CD29 were included in the culture. These T cell clones showed heterogeneous proliferation patterns against KGXXXXXXXXXGK-based and KGXXXXXXXXXGKGKK-based combinatorial peptides libraries, in the presence of IL-2. Pattern-match search on a T cell clone resulted in peptide ligand candidates, one of which induced proliferation, as did protein molecules carrying the corresponding sequence. These results indicate that X19 can induce proliferation of peripheral memory T cells, the peptide ligands of which can be determined using combinatorial peptide libraries.

Amino Acid Sequence↗
PubMed2000

Neurons that express the AMPA receptor GluR2/3 subunits in suprachiasmatic nuclei of Syrian hamsters colocalize either vasoactive intestinal peptide, peptide histidine isoleucine or gastrin-releasing peptide.

In mammals, many circadian rhythms are driven by a clock located inside the suprachiasmatic nucleus of the hypothalamus. They are synchronized to environmental light-dark cycles by information coming directly from the retina via glutamatergic afferents. In rodents, retinal fibres make direct synaptic contacts with neurons synthesizing vasoactive intestinal peptide and gastrin-releasing peptide. These two neuropeptides, administered alone or combined with the peptide histidine isoleucine, phase-shift the clock in the same way that light does. Using ICC and light and electron microscopy, our study demonstrates that subunits 2 and 3 of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid-type glutamatergic receptors are colocalized in neurons expressing one or other of these three neuropeptides. Double-labelled neurons were located in the ventral and lateral ventral parts and near the symmetrical plane of the intermediate and caudal thirds of the nucleus. In light microscopy, brown and granular blue stainings of chromogens revealing both antigens were easily identifiable and spatially separated in perikarya. In electron microscopy, almost all the cells observed in these zones expressed the receptor subunits. A few labelled dendritic profiles, some of them post-synaptic, were observed; axon terminals were always unlabelled. Colocalization with vasoactive intestinal peptide and gastrin-releasing peptide was confirmed by the immunogold technique in perikarya and some dendrites. The present study suggests that peptidergic neurons expressing the AMPA receptors are involved in photic entrainment of the clock by the retina without excluding some glutamatergic information coming from other hypothalamic nuclei.

Animals↗
PubMed2001

Evidence for a novel natriuretic peptide receptor that prefers brain natriuretic peptide over atrial natriuretic peptide.

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) exert their physiological actions by binding to natriuretic peptide receptor A (NPRA), a receptor guanylate cyclase (rGC) that synthesizes cGMP in response to both ligands. The family of rGCs is rapidly expanding, and it is plausible that there might be additional, as yet undiscovered, rGCs whose function is to provide alternative signalling pathways for one or both of these peptides, particularly given the low affinity of NPRA for BNP. We have investigated this hypothesis, using a genetically modified (knockout) mouse in which the gene encoding NPRA has been disrupted. Enzyme assays and NPRA-specific Western blots performed on tissues from wild-type mice demonstrate that ANP-activated cGMP synthesis provides a good index of NPRA protein expression, which ranges from maximal in adrenal gland, lung, kidney, and testis to minimal in heart and colon. In contrast, immunoreactive NPRA is not detectable in tissues isolated from NPRA knockout animals and ANP- and BNP-stimulatable GC activities are markedly reduced in all mutant tissues. However, testis and adrenal gland retain statistically significant, high-affinity responses to BNP. This residual response to BNP cannot be accounted for by natriuretic peptide receptor B, or any other known mammalian rGC, suggesting the presence of a novel receptor in these tissues that prefers BNP over ANP.

Adrenal Glands↗
PubMed2000

Expression of proadrenomedullin derived peptides in the mammalian pituitary: co-localization of follicle stimulating hormone and proadrenomedullin N-20 terminal peptide-like peptide in the same secretory granules of the gonadotropes.

Expression of proadrenomedullin-derived peptides in the rat, cow and human pituitary was studied by a variety of techniques. Immunocytochemical detection showed a widespread expression of adrenomedullin peptide in the adenohypophysis and the neural lobe, with low expression in the intermediate pituitary. Proadrenomedullin N-20 terminal peptide (PAMP)-immunoreactivity was also present in the anterior pituitary but showed a more marked heterogeneous distribution, with cells going from very strong to negative immunostaining. Lower levels of PAMP were found in the neural lobe. Interestingly, the distribution of adrenomedullin and PAMP immunoreactivity in the anterior pituitary did not completely overlap. In the present study, we concentrated our efforts to determine which cell type of the adenohypophysis expresses PAMP. Paraffin and semithin serial sections immunostained for PAMP and the classical pituitary hormones revealed that a subpopulation of the gonadotropes expresses high levels of PAMP-immunoreactive material. Ultrastructural analysis clearly showed PAMP-immunoreactivity in the follicle stimulating hormone (FSH)-containing large secretory granules of the gonadotropes, suggesting simultaneous secretion of PAMP and FSH by this cell type. Three mouse adenohypophysis-derived cell lines (AtT20, GH3, and alphaT3-1 derived from corticotropes, lacto/somatotropes and gonadotropes, respectively) were also analysed and showed expression of both proadrenomedullin-derived peptides and their mRNA. Functional studies in these three cell lines showed that neither adrenomedullin nor PAMP was able to stimulate cAMP production in our experimental conditions. Taken together, our results support that proadrenomedullin derived peptides are expressed in the pituitary in cell-specific and not overlapping patterns, that could be explained by differences in postranslational processing. Our data showing costorage of PAMP and FSH in the same secretory granules open a way by which PAMP could be involved in the control of reproductive physiology in a coordinated manner with FSH.

Adrenomedullin↗
PubMed2000

cDNA cloning of bradykinin-potentiating peptides-C-type natriuretic peptide precursor, and characterization of the novel peptide Leu3-blomhotin from the venom of Agkistrodon blomhoffi.

A cDNA clone, 1.8 kb long, was isolated from a venom gland cDNA library of Agkistrodon blomhoffi that encodes a large plurifunctional precursor composed of 263 amino-acid residues. Nucleotide sequence analysis of this clone revealed that sequences which code for blomhotin and a novel peptide Leu3-blomhotin are located in the N-terminal region of the precursor polypeptide, followed by four tandemly aligned sequences which code for three types of bradykinin-potentiating peptide. In the C-terminal region, the sequence for the C-type natriuretic peptide was located along with a preceding processing signal. The deduced amino-acid sequences for the four bradykinin-potentiating peptides coincided exactly with previously known sequences for potentiator B, potentiator C and potentiator E. The actual Leu3-blomhotin peptide was subsequently isolated from the venom of A. blomhoffi and characterized. Leu3-blomhotin possesses contractile activity in isolated rat stomach fundus smooth muscle in the same manner as blomhotin. Furthermore, it was shown that blomhotin and Leu3-blomhotin retained activity to inhibit the angiotensin-converting enzyme.

Amino Acid Sequence↗
PubMed2006

Direct mass spectrometric peptide profiling and fragmentation of larval peptide hormone release sites in Drosophila melanogaster reveals tagma-specific peptide expression and differential processing.

Regulatory peptides represent a diverse group of messenger molecules. In insects, they are produced by endocrine cells as well as secretory neurones within the CNS. Many regulatory peptides are released as hormones into the haemolymph to regulate, for example, diuresis, heartbeat or ecdysis behaviour. Hormonal release of neuropeptides takes place at specialized organs, so-called neurohaemal organs. We have performed a mass spectrometric characterization of the peptide complement of the main neurohaemal organs and endocrine cells of the Drosophila melanogaster larva to gain insight into the hormonal communication possibilities of the fruit fly. Using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and MALDI-TOF-TOF tandem mass spectrometry, we detected 23 different peptides of which five were unpredicted by previous genome screenings. We also found a hitherto unknown peptide product of the capa gene in the ring gland and transverse nerves, suggesting that it might be released as hormone. Our results show that the peptidome of the neurohaemal organs is tagma-specific and does not change during metamorphosis. We also provide evidence for the first case of differential prohormone processing in Drosophila.

Animals↗
PubMed1988

Gastrin-releasing peptide gene-associated peptides are expressed in normal human fetal lung and small cell lung cancer: a novel peptide family found in man.

Mammalian gastrin-releasing peptide (GRP) is found in cells of neuroendocrine and neural origin, and GRP mediates a variety of physiological and trophic responses when it binds to high affinity cell surface receptors on effector cells. Analysis of cDNA clones derived from prepro-GRP mRNAs predict the concurrent expression of a unique series of peptide hormones, the GRP gene-associated peptides (GGAPs). Alternative RNA splicing of the primary GRP gene transcript results in mRNAs that could encode 3 distinct forms of GGAPs. Using specific antisera directed against synthetic peptides representing portions of the predicted GGAPs, we found multiple GGAP forms in the endocrine cells of human fetal lung and in human small cell lung cancer cells (SCLC). Within a single pulmonary endocrine cell, at least 2 of these 3 predicted forms could be demonstrated using immunohistochemical techniques. In addition, concordant expression of GRP and GGAPs was found in 10 SCLC cell lines and 3 human SCLC tumors. These findings establish GGAPs as a novel peptide family in man and warrant further investigation into their potential role in normal and malignant growth.

Amino Acid Sequence↗