Biomedical subjects

S St-Pierre

Publications and source records attributed to S St-Pierre.

At least 73 records · Page 4Linked to original sources

PubMed1994

Binding profile of a selective calcitonin gene-related peptide (CGRP) receptor antagonist ligand, [125I-Tyr]hCGRP8-37, in rat brain and peripheral tissues.

The calcitonin gene-related peptide (CGRP) C-terminal fragment human CGRP8-37 acts as a potent antagonist of various in vitro and in vivo effects of CGRP. Its iodinated counterpart, [125I-Tyr] hCGRP8-37, binds with high affinity (KD values between 7.5 x 10(-11)-2.1 x 10(-10) M) to what is apparently a single class of CGRP receptors in brain, atrium and vas deferens membrane preparations. The relative potencies of various CGRP-related fragments and analogs in competing for [125I-Tyr]hCGRP8-37 binding sites were similar in these three preparations, with hCGRP alpha being the most potent competitor, followed by unlabeled hCGRP8-37, the linear agonist [acetamidomethyl-cysteine2,7] hCGRP alpha, and finally by rat amylin-amide and salmon calcitonin. Competition profiles suggested the existence of a single affinity site (except in the case of hCGRP alpha, for which competition binding data were best fitted to two apparent affinity constants in all three tissues), whereas rat amylin-amide revealed two affinity constants in the rat brain. Guanylylimidodiphosphate (100 microM) failed to alter specific [125I-Tyr]hCGRP8-37 binding in the various tissues studied here. Quantitative receptor autoradiography in the rat brain revealed [125I-Tyr]hCGRP8-37 binding sites mostly concentrated in the nucleus accumbens (shell), caudate putamen (tail), amygdaloid body, pontine nuclei, cerebellum and inferior olive, whereas lower quantities of sites were present in the olfactory tubercle, nucleus accumbens (core), medial geniculate, superior colliculus, temporal cortex, inferior colliculus, lateral lemniscus, vestibular nuclei and principal sensory trigeminal nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Conformational and biological studies of neuropeptide Y analogs containing structural alterations.

We evaluated the alpha-helix content, the biological activities and the affinities of a series of neuropeptide Y (NPY) analogs containing structural alterations, mainly in the central portion of the molecule for which a putative alpha-helix arrangement has been proposed. First, we investigated the conformational and pharmacological characteristics of derivatives containing the N-terminal tetrapeptide linked to C-terminal peptide-amide segments of various lengths. In some of these, the missing portion was replaced with epsilon-aminocaproic acid, a flexible arm-linker. Data revealed that (1-4)-Aca-(18-36)NPY is a discontinuous analog almost as potent as the native peptide in a pharmacological preparation enriched in Y2 receptors (rat vas deferens), whereas it is about 5 times less potent in a Y1 bioassay (rabbit saphenous vein). This analog showed a similar profile in [125I]PYY binding assays performed in rat frontoparietal cortex (Y1) and hippocampus (Y2) membrane preparations. In a series of truncated derivatives obtained with the successive removal of the 5-13 to 5-17 segments of the NPY molecule, no apparent correlation was observed between the affinity or potency in bioassays and the alpha-helix content, as measured by circular dichroism spectroscopy. Other truncated analogs, obtained by linking the C-terminal 31-36 fragment to various N-terminal tetrapeptides were also investigated. None showed any affinity in brain membrane preparations (frontoparietal cortex and hippocampus) or activity in the rat vas deferens bioassay. However, a weak short-lasting contraction was measured with some of these analogs in the rabbit saphenous vein, thus suggesting that the 1-4 and 31-36 segments of the molecule contains pharmacophores recognized by the Y1 receptor subtype. The contribution of the arginine residues also was evaluated in relation with the alpha-helix. Their successive substitution with lysine, an excellent helix-promoter, showed that the replacement of Arg-19 or Arg-25, two residues found in the putative alpha-helix, gave active analogs. Furthermore, the substitution of Arg-19 with lysine increased the activity in the rat vas deferens as well as the affinity in the brain membrane binding assays. On the other hand, the substitution of Arg-33 produced a weak agonist, whereas the replacement of Arg-35 generated an inactive analog in the Y2-pharmacological preparation and a very weak competitor in the CNS binding assays. Interestingly, this latter analog was still active in the rabbit saphenous vein, thus identifying the position 35 as an additional potential target for the development of Y1 versus Y2 specific molecules.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1993

The rabbit saphenous vein: a tissue preparation specifically enriched in NPY-Y1 receptor subtype.

Neuropeptide Y (NPY), a co-transmitter in noradrenergic sympathetic nerves of the cardiovascular system, was tested on isolated segments of rabbit saphenous vein. NPY caused strong, long lasting and concentration dependent contraction resistant to adrenergic blockade. PYY, a NPY related peptide, shared this property. As pressor agents, both peptides were about 100-fold more potent than norepinephrine and at their highest concentrations caused a contraction of a similar magnitude as NE. Gradual shortening of N-terminal end of the NPY molecule caused major loss of potency and reduction of intrinsic activity; which suggests that the entire molecule is required to produce full biological activity in this vascular preparation. Addition of [Leu31,Pro34]pNPY, a NPY analog with specific agonist properties at Y1 receptors, mimicked the effect of NPY whereas NPY (13-36), a selective agonist at Y2 receptors, caused a 2 log unit shift to the right of the concentration response curve. These results suggest that the vasoconstrictor effect of NPY in rabbit saphenous vein results from a direct effect on smooth muscle cells and that the receptors involved are of the Y1 subtype.

Animals↗

PubMed1993

Evaluation of truncated neuropeptide Y analogues with modifications of the tyrosine residue in position 1 on Y1, Y2 and Y3 receptor sub-types.

Substitutions of the tyrosine residue in position 1 of truncated neuropeptide Y (N-terminal fragment 1-4 linked to C-terminal fragment 18-36 by the epsilon-aminocaproic acid) produced analogues that compete for specific [125I]polypeptide YY (PYY) binding in the frontoparietal cortex (Y1-enriched) with a profile best fitted to a two site-model with KD values in the low and high nM range, respectively. In the hippocampal membrane preparations (Y2-enriched), halogen substitutions on the aromatic ring generated analogues with competition profiles best fitted to a one-site model, revealing differences between the two binding assays and the interaction of these analogues with the Y1 and Y2 receptor sub-types. In the rat vas deferens (Y2-enriched), all truncated analogues inhibited the twitch response with similar or slightly weaker potency than the native molecule. In contrast, these molecules were markedly less potent than neuropeptide Y (NPY) in the rabbit saphenous vein (Y1-enriched) and the rat distal colon (Y3-enriched). Some of the truncated analogues were inactive at up to microM concentrations in the rat distal colon, demonstrating the distinct structural requirement of the receptor sub-type present in this bioassay. These results revealed that amino acid residues between positions 5 and 17 are critical for the maintenance of optimal affinity for the NPY receptors present in the rabbit saphenous vein and the rat distal colon.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Conformational characterization by circular-dichroism spectroscopy of various fragments and analogs of calcitonin-gene-related peptide.

A conformational study by circular-dichroism spectroscopy of calcitonin-gene-related peptide (CGRP) and related fragments and analogs was carried out in structure-promoting solvent mixtures. The structural characterization of rat CGRP alpha and the two isoforms of human CGRP, alpha and beta, revealed that these peptides possess very similar conformational features. The far-ultraviolet circular-dichroism spectra, in pure water, of human CGRP alpha, (hCGRP alpha), [Acm-Cys2,7]hCGRP alpha, various fragments and analogs indicated that these peptides exhibited predominantly a random-coil conformation. The addition of increasing concentrations of 1,1,1,3,3,3-hexafluoro-2-propanol to the peptide solutions resulted in a transition from a random-coil conformation to a stabilized alpha-helical structure. The substantial loss of helical content measured with [Acm-Cys2,7]hCGRP alpha, [Acm-Cys2,7]hCGRP-(1-24)-CONH2 and hCGRP-(8-37), compared to hCGRP alpha, suggested that the N-terminal disulfide bridge of hCGRP alpha is essential for adopting a highly stabilized alpha-helical conformation. Moreover, the lower helical content of hCGRP-(8-37), as compared to [Acm-Cys2,7]hCGRP alpha, as well as spectroscopic results measured with various fragments and analogs of hCGRP-(8-37) revealed that N-terminal residues found in the peptide segment 1-12 are important for the full conservation of the amphiphilic alpha-helix. In addition, the similar alpha-helical content of hCGRP-(8-37) and hCGRP-(8-18) indicated that the C-terminal segment 19-37 is not essential for the stabilization of the alpha-helix structure.

Amino Acid Sequence↗

PubMed1993

An antibody against the Alzheimer's disease amyloid precursor protein recognizes distinct conformational isoforms.

The Alzheimer's disease amyloid precursor protein (APP) consists of several isoforms, which are extensively post-translationally modified and processed. A monoclonal antibody, MAbE1, was raised against a synthetic peptide from an extracellular domain that is common to all isoforms of APP. Immunoblots and immunolocalization studies on cells of neuronal and other origins demonstrated that this antibody recognized a subclass of APP isoforms when compared to a monoclonal antibody raised against a bacterial fusion protein of APP, MAb22C11. Prominent protein bands of 71 kDa and 120 kDa were only detected on immunoblots of cell lysates and no immunoreactivity was observed in protein samples obtained from cell conditioned media. Immunofluorescence labelling with MAbE1 revealed predominantly perinuclear staining of cells of neuronal and glial origin. The data suggest that this monoclonal antibody detects distinct conformational isoforms of APP present in intracellular compartments.

Alzheimer Disease↗

PubMed1993

CGRP 8-37[correction of 8-27] blocks the inhibition of gastric emptying induced by intravenous injection of alpha-CGRP in rats.

The receptor subtype mediating rat alpha-calcitonin gene-related peptide (alpha-CGRP)-induced inhibition of gastric emptying of a non nutrient solution was tested in conscious rats using the CGRP1 receptor antagonist, CGRP 8-37, and the CCK antagonist, MK-329. Intravenous injection of alpha-CGRP (0.5 micrograms) decreased gastric emptying to 26.5 +/- 5.8% from 46.4 +/- 3.9% in vehicle-treated group. Intravenous injection of CGRP 8-37 (15 micrograms) did not influence gastric emptying but completely prevented alpha-CGRP inhibitory effect whereas the 47% delay in gastric emptying induced by intravenous cholecystokinin-8 (CCK, 0.25 microgram) was not modified. The CCK antagonist, MK-329 (1 mg) reversed CCK- but not alpha-CGRP-induced delay in gastric emptying. These results demonstrate that CGRP 8-37 is a specific tool to block alpha-CGRP inhibitory action on gastric motor function and suggest that gastric stasis elicited by peripheral injection of alpha-CGRP may involve an interaction with a CGRP1 receptor subtype.

Animals↗

PubMed1993

Atypical neuroleptic-like behavioral effects of neurotensin.

To better characterize the neuroleptic-like properties of neurotensin, the dose-related effects of the peptide on the following behavioral phenomena were examined: a) the yawning-penile erection syndrome induced by small doses of the dopamine agonists apomorphine and N-propylnorapomorphine (NPA); b) yawning produced by the anticholinesterase physostigmine, and c) stereotyped climbing and sniffing produced by a larger dose of apomorphine. Several doses of the peptide were injected intraventricularly 30 min prior to drug administration. Results indicate that neurotensin markedly decreased yawning and penile erections produced by both apomorphine and NPA. These effects were seen with relatively small doses (0.9-3.75 micrograms). Neurotensin also potently decreased physostigmine-induced yawning with the initial inhibitory effect seen with 50 ng of the peptide. Apomorphine-induced climbing was significantly attenuated with 30.0 and 60.0 micrograms neurotensin, whereas stereotyped sniffing was unaffected, even by doses as large as 120.0 micrograms. These findings suggest that neurotensin might antagonize dopamine autoreceptors and indicate that the peptide possess central anticholinergic activity. Furthermore, these results lend support to the hypothesis that neurotensin's profile of central actions resemble that of atypical neuroleptics.

Animals↗

PubMed1993

Antagonism of the inhibitory action of neuropeptide Y (NPY) in guinea-pig trachea by the C-terminal fragment NPY (2-36).

The C-terminal fragment of neuropeptide Y (NPY), NPY(2-36) was used as a means of discriminating between two differently located NPY receptor sites in guinea-pig trachea. Both NPY and NPY(2-36) reduced the maximal relaxation elicited by vasoactive intestinal peptide (VIP). In contrast, the C-terminal fragment did not mimic the inhibitory action of NPY on the noradrenaline-(NA) evoked response. However, pretreatment of the trachea with 30 nM NPY(2-36), 5 min before generating NA and VIP concentration-response curves in the presence of NPY, abolished the inhibitory effect of NPY on NA-elicited response but did not affect the modulatory action of NPY on VIP-induced relaxation. These results suggest that the two differently located NPY receptor sites in guinea-pig trachea are of two distinct subpopulations.

Animals↗

PubMed1993

Evidence for in vivo interactions between neuropeptide Y-related peptides and sigma receptors in the mouse hippocampal formation.

Recently, it was proposed that neuropeptide Y (NPY) and peptide YY (PYY) could act as endogenous ligands for sigma binding sites, as both NPY and PYY competed with high affinity (nanomolar) for 3H-(+)SKF 10,047 binding sites in rat brain membrane homogenates (Roman et al., 1989). However, various laboratories failed to replicate these in vitro findings. In order to clarify this apparent discrepancy and investigate further possible interactions between NPY and sigma related sites, we evaluated the effects of NPY, PYY and homologs, as well as nonrelated peptides, on in vivo 3H-(+)SKF 10,047 binding parameters in the mouse hippocampal formation. As expected, haloperidol (2 mg/kg), a prototypical sigma receptor ligand, competed for 90% of in vivo hippocampal labeling observed following a peripheral intravenous injection of 3H-(+)SKF 10,047. Intracerebroventricular injections of 300-3000 pmol of either NPY, PYY, NPY2-36, or the Y1 agonist Leu31,Pro34-NPY inhibited significant proportions (17-35%) of haloperidol-sensitive in vivo 3H-(+)SKF 10,047 hippocampal labeling. However, a Y2 receptor agonist, NPY13-36, and nonrelated peptides such as neurotensin and vasoactive intestinal polypeptide, as well as adrenalin, failed to alter in vivo 3H-(+)SKF 10,047 hippocampal binding. It thus appears that NPY, PYY, and a selective Y1 agonist can interact in a concentration-dependent manner, with in vivo 3H-(+)SKF 10,047 labeling in the mouse hippocampal formation. This effect demonstrates selectivity as a Y2 agonist, unrelated peptides, and adrenalin failed to alter in vivo sigma labeling. This in vivo interaction may be relevant to some of the respective biological actions of NPY and sigma-related molecules.

Animals↗

PubMed1993

Comparative characterization and autoradiographic distribution of neuropeptide Y receptor subtypes in the rat brain.

Some evidence has suggested the existence and differential distribution of neuropeptide Y (NPY) receptor subtypes in the mammalian brain (Dumont et al., 1990; Aicher et al., 1991). We now report on the extensive characterization and visualization of at least two classes of NPY receptor sites using a highly selective Y1 analog, [Leu31,Pro34]-NPY or [Pro34]-NPY, and a relatively specific Y2 competitor, NPY13-36. Autoradiographic studies using 125I-peptide YY (125I-PYY) clearly reveal that the Y1 receptor subtype is most abundant in various cortical areas, the dentate gyrus of the hippocampal formation, the claustrum, and the reuniens nucleus of the thalamus. In most other regions, 125I-PYY binding is potently inhibited by increasing concentrations of either NPY2-36 or NPY13-36, suggesting a Y2-like profile. Furthermore, binding assays using homogenates from discrete brain regions clearly demonstrate that various NPY fragments and analogs compete for 125I-PYY labeling with profiles indicative of heterogeneity of NPY receptor subtypes, even in the presence of a selective Y1 blocker. Thus, it is likely that, in addition to the Y1 receptor, which is particularly concentrated in cortical areas, the rat brain is enriched with a receptor class (Y2) that can exist under high- or low-affinity states or with additional receptor subtypes that are recognized by 125I-PYY. These findings cannot be explained by the existence of the very recently reported Y3 receptor subtype, since PYY does not possess significant affinity to this site (Grundemar et al., 1991). Further experiments are currently in progress to determine the nature and functional significance of each of these NPY/PYY receptor sites.

Animals↗

PubMed1992