Structure-activity relationships of neuropeptide Y Y1 receptor antagonists related to BIBP 3226

RF-amide neuropeptides and their receptors in Mammals: Pharmacological properties, drug development and main physiological functions

RF-amide neuropeptides, with their typical Arg-Phe-NH2 signature at their carboxyl C-termini, belong to a lineage of peptides that spans almost the entire life tree. Throughout evolution, RF-amide peptides and their receptors preserved fundamental roles in reproduction and feeding, both in Vertebrates and Invertebrates. The scope of this review is to summarize the current knowledge on the RF-amide systems in Mammals from historical aspects to therapeutic opportunities. Taking advantage of the most recent findings in the field, special focus will be given on molecular and pharmacological properties of RF-amide peptides and their receptors as well as on their implication in the control of different physiological functions including feeding, reproduction and pain. Recent progress on the development of drugs that target RF-amide receptors will also be addressed.

Anxiogenic and Stressor Effects of the Hypothalamic Neuropeptide RFRP-3 Are Overcome by the NPFFR Antagonist GJ14

RFamide-related peptide-3 (RFRP-3) is a recently discovered neuropeptide that has been proposed to play a role in the stress response. We aimed to elucidate the role of RFRP-3 and its receptor, neuropeptide FF (NPFF1R), in modulation of stress and anxiety responses. To achieve this, we characterized a new NPFF1R antagonist because our results showed that the only commercially available putative antagonist, RF9, is in fact an agonist at both NPFF1R and the kisspeptin receptor (KISS1R). We report here the identification and pharmacological characterization of GJ14, a true NPFFR antagonist. In in vivo tests of hypothalamic-pituitary-adrenal (HPA) axis function, GJ14 completely blocked RFRP-3-induced corticosterone release and neuronal activation in CRH neurons. Furthermore, chronic infusion of GJ14 led to anxiolytic-like behavior, whereas RFRP-3 infusion had anxiogenic effects. Mice receiving chronic RFRP-3 infusion also had higher basal circulating corticosterone levels. These results indicate a stimulatory action of RFRP-3 on the HPA axis, consistent with the dense expression of NPFF1R in the vicinity of CRH neurons. Importantly, coinfusion of RFRP-3 and GJ14 completely reversed the anxiogenic and HPA axis-stimulatory effects of RFRP-3. Here we have established the role of RFRP-3 as a regulator of stress and anxiety. We also show that GJ14 can reverse the effects of RFRP-3 both in vitro and in vivo. Infusion of GJ14 causes anxiolysis, revealing a novel potential target for treating anxiety disorders.

Computational prediction of alanine scanning and ligand binding energetics in G-protein coupled receptors

Site-directed mutagenesis combined with binding affinity measurements is widely used to probe the nature of ligand interactions with GPCRs. Such experiments, as well as structure-activity relationships for series of ligands, are usually interpreted with computationally derived models of ligand binding modes. However, systematic approaches for accurate calculations of the corresponding binding free energies are still lacking. Here, we report a computational strategy to quantitatively predict the effects of alanine scanning and ligand modifications based on molecular dynamics free energy simulations. A smooth stepwise scheme for free energy perturbation calculations is derived and applied to a series of thirteen alanine mutations of the human neuropeptide Y1 receptor and series of eight analogous antagonists. The robustness and accuracy of the method enables univocal interpretation of existing mutagenesis and binding data. We show how these calculations can be used to validate structural models and demonstrate their ability to discriminate against suboptimal ones.

The neuropeptide y y(1) receptor: a diagnostic marker? Expression in mcf-7 breast cancer cells is down-regulated by antiestrogens in vitro and in xenografts

The neuropeptide Y (NPY) Y(1) receptor (Y(1)R) has been suggested as a tumor marker for in vivo imaging and as a therapeutic target. In view of the assumed link between estrogen receptor (ER) and Y(1)R in mammary carcinoma and with respect to the development of new diagnostic tools, we investigated the Y(1)R protein expression in human MCF-7 cell variants differing in ER content and sensitivity against antiestrogens. ER and Y(1)R expression were quantified by radioligand binding using [(3)H]-17β-estradiol and the Y(1)R selective antagonist [(3)H]-UR-MK114, respectively. The latter was used for cellular binding studies and for autoradiography of MCF-7 xenografts. The fluorescent ligands Cy5-pNPY (universal Y(1)R, Y(2)R and Y(5)R agonist) and UR-MK22 (selective Y(1)R antagonist), as well as the selective antagonists BIBP3226 (Y(1)R), BIIE0246 (Y(2)R) and CGP71683 (Y(5)R) were used to identify the NPY receptor subtype(s) by confocal microscopy. Y(1)R functionality was determined by mobilization of intracellular Ca(2+). Sensitivity of MCF-7 cells against antiestrogen 4-hydroxytamoxifen correlated directly with the ER content. The exclusive expression of Y(1)Rs was confirmed by confocal microscopy. The Y(1)R protein was up-regulated (100%) by 17β-estradiol (EC(50) 20 pM) and the predominant role of ERα was demonstrated by using the ERα-selective agonist "propylpyrazole triol". 17β-Estradiol-induced over-expression of functional Y(1)R protein was reverted by the antiestrogen fulvestrant (IC(50) 5 nM) in vitro. Furthermore, tamoxifen treatment of nude mice resulted in an almost total loss of Y(1)Rs in MCF-7 xenografts. In conclusion, the value of the Y(1)R as a target for therapy and imaging in breast cancer patients may be compromised due to Y(1)R down-regulation induced by hormonal (antiestrogen) treatment.

Isosteric N-arylpiperazine replacements in a series of dihydropyridine NPY1 receptor antagonists

4-Amino-N-arylpiperidines serve as effective bioisosteres for N-arylpiperazines in the series of dihydropyridine NPY1 receptor antagonists. These were prepared by a ZnCl2-mediated reductive amination reaction between elaborated primary amines, 2 or 5, and 4-arylpiperidones.

Pharmacological characterization of human NPFF1 and NPFF2 receptors expressed in CHO cells by using NPY Y1 receptor antagonists

Neuropeptide FF (NPFF) belongs to an opioid-modulatory system including two precursors (pro-NPFF(A) and pro-NPFF(B)) and two G-protein coupled receptors (NPFF(1) and NPFF(2)). The pharmacological and functional profiles of human NPFF(1) and NPFF(2) receptors expressed in Chinese hamster ovary (CHO) cells were compared by determining the affinity of several peptides derived from both NPFF precursors and by measuring their abilities to inhibit forskolin-induced cAMP accumulation. Each NPFF receptor recognizes peptides from both precursors with nanomolar affinities, however, with a slight preference of pro-NPFF(A) peptides for NPFF(2) receptors and of pro-NPFF(B) peptides for NPFF(1) receptors. BIBP3226 ((R)-N(2)-(diphenylacetyl)-N-[(4-hydroxyphenyl)-methyl]-argininamide) and BIBO3304 ((R)-N(2)-(diphenylacetyl)-N-[4-(aminocarbonylaminomethyl)-benzyl]-argininamide trifluoroacetate), two selective neuropeptide Y (NPY) Y(1) receptor antagonists, display relative high affinities for NPFF receptors and exhibit antagonist properties towards hNPFF(1) receptors. The structural determinants responsible for binding of these molecules to NPFF receptors were investigated and led to the synthesis of hNPFF(1) receptor antagonists with affinities from 40 to 80 nM. Our results demonstrate differences in pharmacological characteristics between NPFF(1) and NPFF(2) receptors and the feasibility of subtype-selective antagonists.