In vitro and in vivo pharmacological characterization of the novel neuropeptide S receptor ligands QA1 and PI1

Neuropeptide S Receptor as an Innovative Therapeutic Target for Parkinson Disease

Parkinson disease (PD) is a neurodegenerative disease mainly characterized by the loss of nigral dopaminergic neurons in the substantia nigra pars compacta. Patients suffering from PD develop severe motor dysfunctions and a myriad of non-motor symptoms. The treatment mainly consists of increasing central dopaminergic neurotransmission and alleviating motor symptoms, thus promoting severe side effects without modifying the disease’s progress. A growing body of evidence suggests a close relationship between neuropeptide S (NPS) and its receptor (NPSR) system in PD: (i) double immunofluorescence labeling studies showed that NPSR is expressed in the nigral tyrosine hydroxylase (TH)-positive neurons; (ii) central administration of NPS increases spontaneous locomotion in naïve rodents; (iii) central administration of NPS ameliorates motor and nonmotor dysfunctions in animal models of PD; (iv) microdialysis studies showed that NPS stimulates dopamine release in naïve and parkinsonian rodents; (v) central injection of NPS decreases oxidative damage to proteins and lipids in the rodent brain; and, (vi) 7 days of central administration of NPS protects from the progressive loss of nigral TH-positive cells in parkinsonian rats. Taken together, the NPS/NPSR system seems to be an emerging therapeutic strategy for alleviating motor and non-motor dysfunctions of PD and, possibly, for slowing disease progress.

Neuropeptide S Receptor Stimulation Excites Principal Neurons in Murine Basolateral Amygdala through a Calcium-Dependent Decrease in Membrane Potassium Conductance

Background: The neuropeptide S system, consisting of the 20 amino acid neuropeptide NPS and its G-protein-coupled receptor (GPCR) neuropeptide S receptor 1 (NPSR1), has been studied intensively in rodents. Although there is a lot of data retrieved from behavioral studies using pharmacology or genetic interventions, little is known about intracellular signaling cascades in neurons endogenously expressing the NPSR1. Methods: To elucidate possible G-protein-dependent signaling and effector systems, we performed whole-cell patch-clamp recordings on principal neurons of the anterior basolateral amygdala of mice. We used pharmacological interventions to characterize the NPSR1-mediated current induced by NPS application. Results: Application of NPS reliably evokes inward-directed currents in amygdalar neurons recorded in brain slice preparations of male and female mice. The NPSR1-mediated current had a reversal potential near the potassium reversal potential (E_K) and was accompanied by an increase in membrane input resistance. GDP-β-S and BAPTA, but neither adenylyl cyclase inhibition nor 8-Br-cAMP, abolished the current. Intracellular tetraethylammonium or 4-aminopyridine reduced the NPS-evoked current. Conclusion: NPSR1 activation in amygdalar neurons inhibits voltage-gated potassium (K⁺) channels, most likely members of the delayed rectifier family. Intracellularly, G_αq signaling and calcium ions seem to be mandatory for the observed current and increased neuronal excitability.

Structure-Activity Relationship Studies on Oxazolo[3,4-a]pyrazine Derivatives Leading to the Discovery of a Novel Neuropeptide S Receptor Antagonist with Potent In Vivo Activity

Neuropeptide S modulates important neurobiological functions including locomotion, anxiety, and drug abuse through interaction with its G protein-coupled receptor known as neuropeptide S receptor (NPSR). NPSR antagonists are potentially useful for the treatment of substance abuse disorders against which there is an urgent need for new effective therapeutic approaches. Potent NPSR antagonists in vitro have been discovered which, however, require further optimization of their in vivo pharmacological profile. This work describes a new series of NPSR antagonists of the oxazolo[3,4-a]pyrazine class. The guanidine derivative 16 exhibited nanomolar activity in vitro and 5-fold improved potency in vivo compared to SHA-68, a reference pharmacological tool in this field. Compound 16 can be considered a new tool for research studies on the translational potential of the NPSergic system. An in-depth molecular modeling investigation was also performed to gain new insights into the observed structure-activity relationships and provide an updated model of ligand/NPSR interactions.

Physiology, pharmacology, and pathophysiology of neuropeptide S receptor

Neuropeptide S receptor 1 (NPSR1), originally named G protein-coupled receptor 154 (GPR154), was deorphanized in 2002 with neuropeptide S identified as the endogenous ligand. NPSR1 is primarily expressed in bronchus, brain as well as immune cells. It regulates multiple physiological processes, including immunoregulation, locomotor activity, anxiety, arousal, learning and memory, and food intake and energy balance. SNPs of NPSR1 are significantly associated with several diseases, including asthma, anxiolytic and arousal disorders, and rheumatoid arthritis. This chapter will summarize studies on NPSR1, including its molecular structure, tissue distribution, physiology, pharmacology, and pathophysiology.

Small Molecule Neuropeptide S and Melanocortin 4 Receptor Ligands as Potential Treatments for Substance Use Disorders

There is a vital need for novel approaches and biological targets for drug discovery and development. Treatment strategies for substance use disorders (SUDs) to date have been mostly ineffective other than substitution-like therapeutics. Two such targets are the peptide G-protein-coupled receptors neuropeptide S (NPS) and melanocortin 4 (MC4). Preclinical evidence suggests that antagonists, inverse agonists, or negative allosteric modulators of these receptors might be novel therapeutics for SUDs. NPS is a relatively unexplored receptor with high potential for treating SUD. MC4 has a strong link to early-onset obesity, and emerging evidence suggests significant overlap between food-maintained and drug-maintained behaviors making MC4 an intriguing target for SUD. This chapter provides an overview of the literature in relation to the roles of NPS and MC4 in drug-seeking behaviors and then provides a medicinal chemistry-based survey of the small molecule ligands for each receptor.

Neuropeptide S receptor ligands: a patent review (2005-2016)

INTRODUCTION

Neuropeptide S (NPS) is a 20-residue peptide and endogenous ligand of the NPS receptor (NPSR). This receptor was a formerly orphan GPCR whose activation increases calcium and cyclic adenosine monophosphate levels. The NPS/NPSR system is expressed in several brain regions where it controls important biological functions including locomotor activity, arousal and sleep, anxiety, food intake, memory, pain, and drug addiction. Areas covered: This review furnishes an updated overview of the patent literature covering NPSR ligands since 2005, when the first example of an NPSR antagonist was disclosed. Expert opinion: Several potent NPSR antagonists are available as valuable pharmacological tools despite showing suboptimal pharmacokinetic properties in vivo. The optimization of these ligands is needed to speed up their potential clinical advancement as pharmaceuticals to treat drug addiction. In order to support the design of novel NPSR antagonists, we performed a ligand-based conformational analysis recognizing some structural requirements for NPSR antagonism. The identification of small-molecule NPSR agonists now represents an unmet challenge to be addressed. These molecules will allow investigation of the beneficial effects of selective NPSR activation in a large panel of psychiatric disorders and to foresee their therapeutic potential as anxiolytics, nootropics, and analgesics.

Paradoxical response to the sedative effects of diazepam and alcohol in C57BL/6J mice lacking the neuropeptide S receptor

The neuropeptide S (NPS) system is characterized by a unique pharmacology because it has anxiolytic-like effects and promotes arousal and wakefulness. To shed light on this peptidergic system, we tested the sedative effect of the central depressants diazepam and ethanol on the loss of righting reflex in mice lacking the neuropeptide S receptor (NPSR), NPSR(-/-). Furthermore, we tested the effect of the intracerebroventricular (ICV) administration of NPS on the sedative effect of diazepam and ethanol in NPSR(-/-) and their wild type counterpart NPSR(+/+). Finally, we evaluated the effect of the pro-arousal neuropeptides CRF and Hcrt-1/Ox-A in NPSR-deficient mice. Contrary to our expectations, the results showed that the NPSR(-/-) were less sensitive to the hypnotic effects of both diazepam and ethanol compared with their wild type littermates. ICV NPS was able to attenuate the sedative effect of both alcohol and diazepam in wild type mice, but not in the NPSR(-/-) line. The administration of CRF and Hcrt-1/Ox-A, two classic pro-arousal peptides, elicited the same effects in both NPSR(-/-) and wild type mice, ruling out the possibility that adaptive mechanisms occurring at the level of these two systems could have occurred during NPSR(-/-) development to compensate for the lack of NPSR receptors. Our findings demonstrated that the deletion of NPSR leads to minor changes in the arousal behavior of mice. Moreover, we demonstrated that the deletion of NPSR did not lead to compensatory changes in the vigilance-promoting effects of the CRF and Hcrt-1/Ox-A systems.

A single-nucleotide polymorphism of human neuropeptide s gene originated from Europe shows decreased bioactivity

Using accumulating SNP (Single-Nucleotide Polymorphism) data, we performed a genome-wide search for polypeptide hormone ligands showing changes in the mature regions to elucidate genotype/phenotype diversity among various human populations. Neuropeptide S (NPS), a brain peptide hormone highly conserved in vertebrates, has diverse physiological effects on anxiety, fear, hyperactivity, food intake, and sleeping time through its cognate receptor-NPSR. Here, we report a SNP rs4751440 (L⁶-NPS) causing non-synonymous substitution on the 6^th position (V to L) of the NPS mature peptide region. L⁶-NPS has a higher allele frequency in Europeans than other populations and probably originated from European ancestors ∼25,000 yrs ago based on haplotype analysis and Approximate Bayesian Computation. Functional analyses indicate that L⁶-NPS exhibits a significant lower bioactivity than the wild type NPS, with ∼20-fold higher EC₅₀ values in the stimulation of NPSR. Additional evolutionary and mutagenesis studies further demonstrate the importance of the valine residue in the 6^th position for NPS functions. Given the known physiological roles of NPS receptor in inflammatory bowel diseases, asthma pathogenesis, macrophage immune responses, and brain functions, our study provides the basis to elucidate NPS evolution and signaling diversity among human populations.