Neuropeptide S Receptor Antagonist Research Articles

Neuropeptide S Receptor: Recent Updates on Nonpeptide Antagonist Discovery

Neuropeptide S (NPS) is a 20-amino acid peptide of great interest due to its possible involvement in several biological processes, including food intake, locomotion, wakefulness, arousal, and anxiety. Structure-activity relationship studies of NPS have identified key points for structural modifications with the goal of modulating NPS receptor (NPSR) agonist activity or achieving antagonism at the same receptor. Only limited information is available for nonpeptide NPSR antagonists. In the last year, several studies have been reported in literature which present various series of small molecules as antagonists of this receptor. The results allow a comparison of the structures and activities of these molecules, leading to the design of new ligands with increased potency and improved pharmacological and pharmacokinetic profiles. This work presents a brief overview of the available information regarding structural features and pharmacological characterization of published nonpeptide NPSR antagonists.

Neuropeptide S facilitates cue-induced relapse to cocaine seeking through activation of the hypothalamic hypocretin system

Drug addiction is a chronic relapsing disorder characterized by compulsive drug seeking and use. Environmental conditioning factors are among the major determinants of relapse in abstinent cocaine users. Here we describe a role of the neuropeptide S (NPS) system in regulating relapse. In rats with a history of cocaine self-administration, presentation of stimuli predictive of drug availability reinstates drug seeking, triggering relapse. Intracerebroventricular (ICV) injection of NPS increased conditioned reinstatement of cocaine seeking, whereas peripheral administration of the NPS receptor antagonist SHA 68 reduced it. Manipulation of the NPS receptor system did not modify cocaine self-administration. We also found that ICV NPS administration activates c-Fos expression in hypocretin-1/orexin-A (Hcrt-1/Ox-A) immunoreactive neurons in the lateral hypothalamus (LH) and in the perifornical area (PeF). Of note, intra-LH and intra-PeF administration of NPS increased conditioned reinstatement of cocaine responding, an effect that was selectively blocked with the Hcrt-1/Ox-A receptor selective antagonist SB334867. Finally, results showed that intra-LH injection of the NPS antagonist [D-Cys(tBu) (5)]NPS blocked cue-induced cocaine seeking, indicating a role for this system in the pathophysiology of drug relapse.

Effect of neuropeptide S receptor antagonists and partial agonists on palatable food consumption in the rat

Neuropeptide S (NPS) is the endogenous ligand for the previously orphan G-protein-coupled-receptor, now termed NPS receptor (NPSR). NPS has both anxiolytic and pro-arousal properties and decreases food intake. In this work we use a rat model of palatable food intake to test in vivo different analogs of human NPS developed in our laboratories and characterized in previous in vitro experiments as partial agonists ([Ala 3]NPS and [Aib 5]NPS), or antagonists ([ d-Cys( tBu) 5]NPS and [ tBu- d-Gly 5]NPS). Our results confirmed that intracerebroventricular (ICV) injection of NPS (1 nmol) decreases standard chow intake in food restricted rats as well as in freely feeding animals fed with standard or palatable food diets. [Aib 5]NPS (30 and 60 nmol), like NPS, reduced palatable food intake, thus confirming in vivo its ability to activate NPSR. [Ala 3]NPS (60 nmol) did not affect palatable food intake per se but blocked the anorectic effect of NPS, thus suggesting its ability to function as an antagonist in this model. Finally, [ d-Cys( tBu) 5]NPS (20–60 nmol) and [ tBu- d-Gly 5]NPS (10–30 nmol), described in previous in vitro studies as pure NPSR antagonists, did not affect palatable food intake when given alone, but fully blocked the anorectic effect of NPS. These results provide an important characterization of the pharmacological properties of these NPS analogs in vivo. Of particular relevance are the data showing that [ d-Cys( tBu) 5]NPS and [ tBu- d-Gly 5]NPS behave as pure antagonists at NPSR regulating food intake, indicating that these molecules are suitable tools for further investigation of the physiopharmacology of the NPS/NPSR system.

Central Neuropeptide S inhibits food intake in mice through activation of Neuropeptide S receptor

Neuropeptide S (NPS), the endogenous ligand of NPS receptor (NPSR), can regulate a variety of biological functions, including arousal, anxiety, locomotion, memory and drug abuse. Previous studies have shown that central NPS inhibited food intake in rats and chicks. In the present study, we investigated the role of central NPS on food intake in fasted mice, and detected the underlying mechanism(s) by using NPSR antagonist [D-Val 5]NPS and Corticotropin-Releasing Factor 1 (CRF 1) Receptor antagonist NBI-27914. The present results indicated that intracerebroventricular injection of NPS (0.001–0.1 nmol) dose-dependently inhibited food intake in fasted mice. The anorectic effect of NPS reached the maximum at the dose of 0.1 nmol, which could be antagonized by co-injection of 10 nmol NPSR antagonist [D-Val 5]NPS. Furthermore, CRF 1 receptor antagonist NBI-27914 at the dose of 2 μg antagonized the hyperlocomotor action of NPS, but did not affect the role of NPS on food intake. In conclusion, our results demonstrated central NPS inhibited food intake in fasted mice, mediated by its cognate NPSR, but not by CRF 1 receptor.

Further studies on the pharmacological profile of the neuropeptide S receptor antagonist SHA 68

Neuropeptide S (NPS) regulates various biological functions by selectively activating the NPS receptor (NPSR). Previous studies demonstrated that the non-peptide molecule SHA 68 acts as a selective NPSR antagonist. In the present study the pharmacological profile of SHA 68 has been further investigated in vitro and in vivo. In cells expressing the mouse NPSR SHA 68 was inactive per se up to 10 μM while it antagonized NPS-stimulated calcium mobilization in a competitive manner showing a p A 2 value of 8.06. In the 10–50 mg/kg range of doses, SHA 68 counteracted the stimulant effects elicited by NPS, but not those of caffeine, in mouse locomotor activity experiments. In the mouse righting reflex assay SHA 68 fully prevented the arousal-promoting action of the peptide. The anxiolytic-like effects of NPS were slightly reduced by SHA 68 in the mouse open field, fully prevented in the rat elevated plus maze and partially antagonized in the rat defensive burying paradigm. Finally, SHA 68 was found poorly active in antagonizing the NPS inhibitory effect on palatable food intake in rats. In all assays SHA 68 did not produce any effect per se. In conclusion, the present study demonstrated that SHA 68 behaves as a selective NPSR antagonist that can be used to characterize the in vivo actions of NPS. However the usefulness of this research tool is limited by its poor pharmacokinetic properties.

Further Studies at Neuropeptide S Position 5: Discovery of Novel Neuropeptide S Receptor Antagonists

Neuropeptide S (NPS) regulates various biological functions by activating the NPS receptor (NPSR). Previous studies demonstrated that the substitution of Gly(5) with d-amino acids generates NPSR antagonists. Eleven [d-Xaa(5)]NPS derivatives were synthesized and pharmacologically tested measuring [Ca(2+)](i) in HEK293(mNPSR) cells. The results confirmed that the [d-Xaa(5)] substitution promotes antagonist activity with potency inversely related to the side chain size and allowed identification of the novel potent NPSR peptide antagonist [(t)Bu-d-Gly(5)]NPS.

Central Neuropeptide S inhibits distal colonic transit through activation of central Neuropeptide S receptor in mice

Neuropeptide S (NPS), the endogenous ligand of NPS receptor (NPSR), regulates many biological functions, including arousal, anxiety, locomotion and food intake. NPSR mRNA is expressed in several regions of central autonomic network through which the brain controls visceromotor and other responses essential for survival. However, the role of NPS/NPSR system in regulating gastrointestinal motor is still unknown. Here, we studied the effects of NPS on distal colonic transit in mice. Intracerebroventricular (i.c.v.) injection of NPS (1–1000 pmol) inhibited fecal pellet output and bead expulsion in a dose-dependent manner. However, intraperitoneal injection of NPS (1000 and 10 000 pmol) did not affect fecal pellet output and bead expulsion. In vitro, NPS (0.1–10 μM) also did not modulate distal colonic contractions. Furthermore, i.c.v. co-administration of [D-Val 5]NPS, a pure and potent NPSR antagonist, dose-dependently antagonized the inhibitory effects of NPS on fecal pellet output and bead expulsion. In conclusion, our results firstly indicate that central NPS inhibits distal colonic transit through the activation of central NPSR, which implicate that NPS/NPSR system might be a new target to treat function disorder of distal colon.

In Vitro and in Vivo Pharmacological Characterization of the Neuropeptide S Receptor Antagonist [d-Cys(tBu)5]Neuropeptide S

Neuropeptide S (NPS) was identified as the endogenous ligand of an orphan receptor now referred to as the NPS receptor (NPSR). In the frame of a structure-activity study performed on NPS Gly5, the NPSR ligand [D-Cys(tBu)(5)]NPS was identified. [D-Cys(tBu)(5)]NPS up to 100 microM did not stimulate calcium mobilization in human embryonic kidney (HEK) 293 cells stably expressing the mouse NPSR; however, in a concentration-dependent manner, the peptide inhibited the stimulatory effects elicited by 10 and 100 nM NPS (pK(B), 6.62). In Schild analysis experiments [D-Cys(tBu)(5)]NPS (0.1-100 microM) produced a concentration-dependent and parallel rightward shift of the concentration-response curve to NPS, showing a pA(2) value of 6.44. Ten micromolar [D-Cys(tBu)(5)]NPS did not affect signaling at seven NPSR unrelated G-protein-coupled receptors. In the mouse righting reflex (RR) recovery test, NPS given at 0.1 nmol i.c.v. reduced the percentage of animals losing the RR in response to 15 mg/kg diazepam and their sleeping time. [d-Cys(tBu)(5)]NPS (1-10 nmol) was inactive per se but dose-dependently antagonized the arousal-promoting action of NPS. Finally, NPSR-deficient mice were similarly sensitive to the hypnotic effects of diazepam as their wild-type littermates. However, the arousal-promoting action of 1 nmol NPS could be detected in wild-type but not in mutant mice. In conclusion, [D-Cys(tBu)(5)]NPS behaves both in vitro and in vivo as a pure and selective NPSR antagonist but with moderate potency. Moreover, using this tool together with receptor knockout mice studies, we demonstrated that the arousal-promoting action of NPS is because of the selective activation of the NPSR protein.

Neuropeptide S-Mediated Control of Fear Expression and Extinction: Role of Intercalated GABAergic Neurons in the Amygdala

A deficient extinction of memory is particularly important in the regime of fear, where it limits the beneficial outcomes of treatments of anxiety disorders. Fear extinction is thought to involve inhibitory influences of the prefrontal cortex on the amygdala, although the detailed synaptic mechanisms remain unknown. Here, we report that neuropeptide S (NPS), a recently discovered transmitter of ascending brainstem neurons, evokes anxiolytic effects and facilitates extinction of conditioned fear responses when administered into the amygdala in mice. An NPS receptor antagonist exerts functionally opposing responses, indicating that endogenous NPS is involved in anxiety behavior and extinction. Cellularly, NPS increases glutamatergic transmission to intercalated GABAergic neurons in the amygdala via presynaptic NPS receptors on connected principal neurons. These results identify mechanisms of NPS in the brain, a key role of intercalated neurons in the amygdala for fear extinction, and a potential pharmacological avenue for treating anxiety disorders.

Conformation−Activity Relationship of Neuropeptide S and Some Structural Mutants: Helicity Affects Their Interaction with the Receptor

Neuropeptide S (NPS) is the endogenous ligand of the previously orphan G-protein coupled receptor now named NPSR. The NPS-NPSR receptor system regulates important biological functions such as sleep/waking, locomotion, anxiety and food intake. Recently, exhaustive Ala scan and d-amino acid scan studies, together with systematic N- and C-terminal truncation, led to the identification of key residues for biological activity. Because conformational preferences might also play an important role, we undertook a detailed conformational analysis of NPS and several analogues in solution. We show that helicity induced by substitution of three flexible residues in the 5-13 regulatory region abolishes biological activity. A parallel pharmacological and conformational study of single and multiple substitutions of glycines 5, 7, and 9 showed that helicity can be tolerated in the C-terminal part of the peptide but not around Gly7. The identification of hNPSR partial agonists heralds the possibility of designing pure NPS receptor antagonists.