Pharmacological characterization and feeding-suppressive property of FMS586 [3-(5,6,7,8-tetrahydro-9-isopropyl-carbazol-3-yl)-1-methyl-1-(2-pyridin-4-yl-ethyl)-urea hydrochloride], a novel, selective, and orally active antagonist for neuropeptide Y Y5 receptor

PET Imaging of the Neuropeptide Y System: A Systematic Review

Neuropeptide Y (NPY) is a vastly studied biological peptide with numerous physiological functions that activate the NPY receptor family (Y₁, Y₂, Y₄ and Y₅). Moreover, these receptors are correlated with the pathophysiology of several diseases such as feeding disorders, anxiety, metabolic diseases, neurodegenerative diseases, some types of cancers and others. In order to deepen the knowledge of NPY receptors' functions and molecular mechanisms, neuroimaging techniques such as positron emission tomography (PET) have been used. The development of new radiotracers for the different NPY receptors and their subsequent PET studies have led to significant insights into molecular mechanisms involving NPY receptors. This article provides a systematic review of the imaging biomarkers that have been developed as PET tracers in order to study the NPY receptor family.

Discovery of a multipotent chaperone, 1-(2,6-Difluorobenzylamino)-3-(1,2,3,4-tetrahydrocarbazol-9-yl)-propan-2-ol with the inhibitory effects on the proliferation of prion, cancer as well as influenza virus

We previously discovered three carbazole derivatives, GJP14 (1-piperidinylmethyl-2-(1-oxo-6-methyl-1,2,3,4-tetrahydrocarbazol-9-yl)-ethan-1-ol) with anti-prion activity, GJC29 (benzylamino-3-(1,2,3,4-tetrahydrocarbazol-9-yl)-propan-2-ol) with anti-cancer activity, and THC19 (1-piperidinylmethyl-2-(1,2,3,4-tetrahydrocarnazol-9-yl)-ethan-1-ol) with anti-influenza virus activity. During optimization of GJP14 for the anti-prion activity, we discovered a compound, 1-(2,6-difluorobenzylamino)-3-(1,2,3,4-tetrahydrocarbazol-9-yl)-propan-2-ol, termed 5Y, had the most strong anti-prion activity among a series of newly synthesized derivatives. Intriguingly, we noticed that 5Y had also the most strong anti-colon cancer as well as the anti-influenza virus activities among derivatives. No significant toxicity of 5Y was observed. These results demonstrate that 5Y is a multipotent lead compound with unusually wide spectrum, and may be applicable to therapeutics targeting multiple diseases.Abbreviations: MoPrP: mouse prion protein of amino acid residues of 23-231; PrP^C: cellular form of prion protein; PrP^Sc: scrapie form of prion protein.

Neuropeptide Y Signaling in the Lateral Hypothalamus Modulates Diet Component Selection and is Dysregulated in a Model of Diet-Induced Obesity

The preclinical multicomponent free-choice high-fat high-sucrose (fcHFHS) diet has strong validity to model diet-induced obesity (DIO) and associated maladaptive molecular changes in the central nervous system. fcHFHS-induced obese rats demonstrate increased sensitivity to intracerebroventricular infusion of the orexigenic Neuropeptide Y (NPY). The brain region-specific effects of NPY signaling on fcHFHS diet component selection are not completely understood. For example, fcHFHS-fed rats have increased intake of chow and fat following intracerebroventricular NPY infusion, whereas NPY administration in the nucleus accumbens, a key hub of the reward circuitry, specifically increases fat intake. Here, we investigated whether NPY infusion in the lateral hypothalamic area (LHA), which is crucially involved in the regulation of intake, regulates fcHFHS component selection, and if LHA NPY receptor subtypes 1 or 5 (NPYR1/5) are involved. Male Wistar rats were fed a chow or fcHFHS diet for at least seven days, and received intra-LHA vehicle or NPY infusions in a cross-over design. Diet component intake was measured two hours later. Separate experimental designs were used to test the efficacy of NPY1R- or NPY5R antagonism to prevent the orexigenic effects of intra-LHA NPY. Intra-LHA NPY increased caloric intake in chow- and fcHFHS-fed rats. This effect was mediated specifically by chow intake in fcHFHS-fed rats. The orexigenic effects of intra-LHA NPY were prevented by NPY1R and NPY5R antagonism in chow-fed rats, but only by NPY5R antagonism in fcHFHS-fed rats. Thus, NPY signaling has brain region-specific effects on fcHFHS component selection and LHA NPYR sensitivity is dysregulated during consumption of a fcHFHS diet.

Can neuropeptides treat obesity? A review of neuropeptides and their potential role in the treatment of obesity

Obesity is a major worldwide public health issue. The physiological systems that regulate body weight are thus of great interest as targets for anti-obesity agents. Peptidergic systems are critical to the regulation of energy homeostasis by key regions in the hypothalamus and brainstem. A number of neuropeptide systems have therefore been investigated as potential treatments for obesity. Blocking orexigenic peptide signals such as neuropeptide Y, melanin-concentrating hormone, orexins, relaxin-3 and galanin-like peptide or stimulating anorectic signalling pathways used by peptides such as the melanocortins, ciliary neurotrophic factor and brain-derived neurotrophic factor, are approaches that have shown some promise, but which have also highlighted possible concerns. Manipulation of central peptidergic systems poses a number of therapeutic problems, including brain access and side effects. Given that the homeostatic defence of body weight may limit the effectiveness of any single-target therapy developed, a combination therapy approach may offer the best hope for the effective prevention and treatment of obesity.

LINKED ARTICLES

This article is part of a themed section on Neuropeptides. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.170.issue-7.

Neuropeptide Y receptors: how to get subtype selectivity

The neuropeptide Y (NPY) system is a multireceptor/multiligand system consisting of four receptors in humans (hY(1), hY(2), hY(4), hY(5)) and three agonists (NPY, PYY, PP) that activate these receptors with different potency. The relevance of this system in diseases like obesity or cancer, and the different role that each receptor plays influencing different biological processes makes this system suitable for the design of subtype selectivity studies. In this review we focus on the latest findings within the NPY system, we summarize recent mutagenesis studies, structure activity relationship studies, receptor chimera, and selective ligands focusing also on the binding mode of the native agonists.

CCK, PYY and PP: the control of energy balance

The control of food intake consists of neural and hormonal signals between the gut and central nervous system (CNS). Gut hormones such as CCK, PYY and PP signal to important areas in the CNS involved in appetite regulation to terminate a meal. These hormones can act directly via the circulation and activate their respective receptors in the hypothalamus and brainstem. In addition, gut vagal afferents also exist, providing an alternative pathway through which gut hormones can communicate with higher centres through the brainstem. Animal and human studies have demonstrated that peripheral administration of certain gut hormones reduces food intake and leads to weight loss. Gut hormones are therefore potential targets in the development of novel treatments for obesity and analogue therapies are currently under investigation.

NPY receptors as potential targets for anti-obesity drug development

The neuropeptide Y system has proven to be one of the most important regulators of feeding behaviour and energy homeostasis, thus presenting great potential as a therapeutic target for the treatment of disorders such as obesity and at the other extreme, anorexia. Due to the initial lack of pharmacological tools that are active in vivo, functions of the different Y receptors have been mainly studied in knockout and transgenic mouse models. However, over recent years various Y receptor selective peptidic and non-peptidic agonists and antagonists have been developed and tested. Their therapeutic potential in relation to treating obesity and other disorders of energy homeostasis is discussed in this review.

Regulation of maternal food intake and mother-pup interactions by the Y5 receptor

Neuropeptide Y (NPY) is increased in the hypothalamus during lactation. To investigate the role of the NPY Y5 receptor during lactation, an antisense oligodeoxynucleotide (ODN) targeted to the NPY Y5 receptor, an equivalent scrambled ODN or vehicle, was chronically infused into the 3rd ventricle of lactating rats from day 8 postpartum. Y5 antisense ODN treatment reduced Y5 positive cell number in the paraventricular nucleus and resulted in significant reductions in food intake and litter growth. Litters from pair-fed vehicle treated dams gained significantly more weight than the litters of Y5 antisense ODN treated dams suggesting that decreased maternal food intake is not the only mechanism involved in suppressing litter weight gain. When mother-litter interaction was examined on day 13 pp, Y5 antisense ODN treated dams spent significantly less time on the nest and had significantly shorter nest bouts. These results suggest that in addition to regulating feeding behaviour, the Y5 receptor subtype may have previously unrecognised roles in the control of nesting behaviour during lactation with subsequent effects on litter growth rates.

Identification and characterization of pseudoirreversible nonpeptide antagonists of the neuropeptide Y Y5 receptor and development of a novel Y5-selective radioligand

The neuropeptide Y (NPY) Y(5) receptor is believed to be involved in the central regulation of appetite. Thus, antagonists of this receptor have been pursued as potential therapeutic agents for the treatment of obesity. A novel series of potent and selective phenylamide or biaryl urea NPY Y(5) receptor antagonists was identified. Four representative compounds from this series, SCH 208639 (N-[4-[(1,1-dimethylbutyl)thio]phenyl]-2,2-dimethylpropanamide), SCH 430765 (N-[[[3'-fluoro[1,1'-biphenyl]-4-yl]amino]carbonyl]-N-methyl-1-(methylsulfonyl)-4-piperidinamine), SCH 488106 (N-[[[3',5'-difluoro[1,1'-biphenyl]-4-yl]amino]carbonyl]-N-methyl-1-[(5-methyl-3-pyridinyl)carbonyl]-4-piperidinamine) and SCH 500946 (N-[[[5-(3,5-difluorophenyl)-2-pyrazinyl]amino]carbonyl]-N-methyl-1-(methylsulfonyl)-4-piperidinamine), behaved as competitive antagonists in radioligand binding assays, but displayed apparently insurmountable antagonism in a cell-based functional assay. The apparently insurmountable antagonism was due to slow receptor dissociation rates rather than covalent binding, because the antagonists' effects could be reduced by extensive washing of cells after antagonist exposure. A novel radioligand, [(35)S]SCH 500946, was also developed and used to characterize the interaction of these antagonists with the NPY Y(5) receptor. [(35)S]SCH 500946 had high affinity for the NPY Y(5) receptor (K(d)=0.29 nM), and the binding kinetics (k(on) 4.414 x 10(7) M(-)(1) min(-1); k(off) 0.009816 min(-1)) confirmed that the compound slowly dissociates from the receptor. In a competition binding assay, NPY failed to displace [(35)S]SCH 500946 completely, indicating that the binding sites for NPY and [(35)S]SCH 500946 are not identical. These data indicate that the apparent insurmountable antagonism of these NPY Y(5) receptor antagonists is attributable both to slow receptor dissociation rates and to binding at a site distinct from NPY.

Discovery of novel orally active ureido NPY Y5 receptor antagonists

We have derived a novel series of neuropeptide Y (NPY) Y5 receptor antagonists from the biphenylurea 3. Cyclohexylurea 21c, a member of the series, is a potent NPY Y5 receptor antagonist that exhibits excellent pharmacokinetic parameters in rats and dogs. On chronic oral administration to diet-induced obese rats, 21c displayed an anti-obesity profile, causing a modest reduction in food intake, a significant decrease in body weight gain, a decrease in adipose mass, and an increase in lean tissue mass.

Neuropeptide y receptor selective ligands in the treatment of obesity

Obesity is a serious public health problem throughout the world, affecting both developed societies and developing countries. The central nervous system has developed a meticulously interconnected circuitry in order to keep us fed and in an adequate nutritional state. One of these consequences is that an energy-dense environment favors the development of obesity. Neuropeptide Y (NPY) is one of the most abundant and widely distributed peptides in the central nervous system of both rodents and humans and has been implicated in a variety of physiological actions. Within the hypothalamus, NPY plays an essential role in the control of food intake and body weight. Centrally administered NPY causes robust increases in food intake and body weight and, with chronic administration, can eventually produce obesity. NPY activates a population of at least six G protein-coupled Y receptors. NPY analogs exhibit varying degrees of affinity and specificity for these Y receptors. There has been renewed speculation that ligands for Y receptors may be of benefit for the treatment of obesity. This review highlights the therapeutic potential of Y(1), Y(2), Y(4), and Y(5) receptor agonists and antagonists as additional intervention to treat human obesity.

Direct evidence that stimulation of neuropeptide Y Y5 receptor activates hypothalamo-pituitary-adrenal axis in conscious rats via both corticotropin-releasing factor- and arginine vasopressin-dependent pathway

An abundance of data suggests a crucial role of neuropeptide Y (NPY) as an activator of the hypothamamo-pituitary-adrenal (HPA) axis. However, there is quite limited evidence regarding receptors that mediate this response. Here, we address the possibility that Y(5) receptor subtype may be responsible for NPY-induced activation of HPA axis. For this purpose, the effects of an intracerebroventricular injection of Y(5)-selective agonist, [cPP(1-7), NPY(19-23), Ala(31), Aib(32), Gln(34)]-human pancreatic polypeptide (hPP), on circulating ACTH and corticosterone in conscious rats were evaluated. Central injection of hPP (100 pmol) produced significant increases in plasma ACTH and corticosterone compared with artificial cerebrospinal fluid, and previous treatment with a novel Y(5)-selective antagonist, FMS586 [3-(9-isopropyl-6,7,8,9-tetrahydro-5H-carbazol-3-yl)-1-methyl-1-(2-pyridin-4-yl-ethyl)-urea hydrochloride] (25 mg/kg, po), completely blocked these alterations. Pretreatment with corticotropin-releasing factor (CRF) receptor antagonist (astressin, 10-50 microg/rat, iv) or arginine vasopressin (AVP) receptor antagonist ([deamino-Pen(1), O-Me-Tyr(2), Arg(8)] vasopressin; 3-30 microg/rat, iv) differentially suppressed these increases by 70-80 or 40-50%, respectively. The combined treatment showed no additive effect of these antagonists. Furthermore, an exogenous AVP (0.3 microg/rat, iv)-induced HPA activation was fully inhibited by astressin, suggesting a convergent pathway of AVP receptor signals onto CRF neurons. Central injection of hPP also evoked marked up-regulation of mRNA expression for CRF and AVP in the hypothalamus, which, likewise, were completely reversed by FMS586. Our observations provide the first evidence that selective stimulation of Y(5) receptor provokes activation of the HPA axis and its downstream pathway is chiefly composed of both CRF (primary regulator) and AVP (subordinate to the former) with distinct relative contribution.