Annette G. Beck-Sickinger

The first highly potent and selective non-peptide neuropeptide Y Y1 receptor antagonist: BIBP3226.

The design and subsequent in vitro and in vivo biological characterisation of the first potent and selective non-peptide neuropeptide Y Y1 receptor antagonist, BIBP3226 ((R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-argininami de) is reported. BIBP3226 displaced 125I-labelled neuropeptide Y with high affinity (Ki = 7 nM) from the human neuropeptide Y Y1 receptor and proved to be highly selective. BIBP3226 displayed potent antagonistic properties both in in vitro and in vivo models and thus represents the first selective non-peptide neuropeptide Y Y1 receptor antagonist.

Neuropeptide Y stimulates neuronal precursor proliferation in the post-natal and adult dentate gyrus

Adult dentate neurogenesis is important for certain types of hippocampal‐dependent learning and also appears to be important for the maintenance of normal mood and the behavioural effects of antidepressants. Neuropeptide Y (NPY), a peptide neurotransmitter released by interneurons in the dentate gyrus, has important effects on mood, anxiety‐related behaviour and learning and memory. We report that adult NPY receptor knock‐out mice have significantly reduced cell proliferation and significantly fewer immature doublecortin‐positive neurons in the dentate gyrus. We also show that the neuroproliferative effect of NPY is dentate specific, is Y1‐receptor mediated and involves extracellular signal‐regulated kinase (ERK)1/2 activation. NPY did not exhibit any effect on cell survival in vitro but constitutive loss of the Y1 receptor in vivo resulted in greater survival of newly generated neurons and an unchanged total number of dentate granule cells. These results show that NPY stimulates neuronal precursor proliferation in the dentate gyrus and suggest that NPY‐releasing interneurons may modulate dentate neurogenesis.

The first selective agonist for the neuropeptide YY5 receptor increases food intake in rats.

The first Y5 receptor-selective analog of neuropeptide Y (NPY), [Ala31,Aib32]NPY, has been developed and biologically characterized. Using competition binding assays on cell lines that express different Y receptors, we determined the affinity of this analog to be 6 nm at the human Y5 receptor, >500 nm at the Y1 and Y2 receptors, and >1000 nm at the Y4 receptor. Activity studies performed in vitro using a cAMP enzyme immunoassay, and in vivousing food intake studies in rats, showed that the peptide acted as an agonist. Further peptides obtained by the combination of the Ala31-Aib32 motif with chimeric peptides containing segments of NPY and pancreatic polypeptide displayed the same selectivity and even higher affinity (up to 0.2 nm) for the Y5 receptor. In vivoadministration of the new Y5 receptor-selective agonists significantly stimulated feeding in rats. The NMR solution structures of NPY and [Ala31,Aib32]NPY showed a different conformation in the C-terminal region, where the α-helix of NPY was substituted by a more flexible, 310-helical turn structure.

Molecular characterization of the ligand–receptor interaction of the neuropeptide Y family

Neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) belong to the NPY hormone family and activate a class of receptors called the Y‐receptors, and also belong to the large superfamily of the G‐protein coupled receptors. Structure–affinity and structure–activity relationship studies of peptide analogs, combined with studies based on site‐directed mutagenesis and anti‐receptor antibodies, have given insight into the individual characterization of each receptor subtype relative to its interaction with the ligand, as well as to its biological function. A number of selective antagonists at the Y1‐receptor are available whose structures resemble that of the C‐terminus of NPY. Some of these compounds, like BIBP3226, BIBO3304 and GW1229, have recently been used for in vivo investigations of the NPY‐induced increase in food intake. Y2‐receptor selective agonists are the analog cyclo‐(28/32)‐Ac‐[Lys28‐Glu32]‐(25–36)‐pNPY and the TASP molecule containing two units of the NPY segment 21–36. Now the first antagonist with nanomolar affinity for the Y2‐receptor is also known, BIIE0246. So far, the native peptide PP has been shown to be the most potent ligand at the Y4‐receptor. However, by the design of PP/NPY chimera, some analogs have been found that bind not only to the Y4‐, but also to the Y5‐receptor with subnanomolar affinities, and are as potent as NPY at the Y1‐receptor. For the characterization of the Y5‐receptor in vitro and in vivo, a new class of highly selective agonists is now available. This consists of analogs of NPY and of PP/NPY chimera which all contain the motif Ala31‐Aib32. This motif has been shown to induce a 310‐helical turn in the region 28–31 of NPY and is suggested to be the key motif for high Y5‐receptor selectivity. The results of feeding experiments in rats treated with the first highly specific Y5‐receptor agonists support the hypothesis that this receptor plays a role in the NPY‐induced stimulation of food intake. In conclusion, the selective compounds for the different Y‐receptor subtypes known so far are promising tools for a better understanding of the physiological properties of the hormones of the NPY family and related receptors. Copyright

Neuropeptide Y is neuroproliferative for post-natal hippocampal precursor cells

New neurones are produced in the adult hippocampus throughout life and are necessary for certain types of hippocampal learning. Little, however, is known about the control of hippocampal neurogenesis. We used primary hippocampal cultures from early post‐natal rats and neuropeptide Y Y1 receptor knockout mice as well as selective neuropeptide Y receptor antagonists and agonists to demonstrate that neuropeptide Y is proliferative for nestin‐positive, sphere‐forming hippocampal precursor cells and β‐tubulin‐positive neuroblasts and that the neuroproliferative effect of neuropeptide Y is mediated via its Y1 receptor. Immunohistochemistry confirmed Y1 receptor staining on both nestin‐positive cells and β‐tubulin‐positive cells in culture and short pulse 5‐bromo‐2‐deoxyuridine studies demonstrated that neuropeptide Y has a proliferative effect on both cell types. These studies suggest that the proliferation of hippocampal neuroblasts and precursor cells is increased by neuropeptide Y and, therefore, that hippocampal learning and memory may be modulated by neuropeptide Y‐releasing interneurones.

The anti-epileptic actions of neuropeptide Y in the hippocampus are mediated by Y2 and not Y5 receptors

Neuropeptide Y (NPY) potently inhibits glutamate release and seizure activity in rodent hippocampus in vitro and in vivo, but the nature of the receptor(s) mediating this action is controversial. In hippocampal slices from rats and several wild‐type mice, a Y2‐preferring agonist mimicked, and the Y2‐specific antagonist BIIE0246 blocked, the NPY‐mediated inhibition both of glutamatergic transmission and of epileptiform discharges in two different slice models of temporal lobe epilepsy, stimulus train‐induced bursting (STIB) and 0‐Mg2+ bursting. Whereas Y5 receptor‐preferring agonists had small but significant effects in vitro, they were blocked by BIIE0246, and a Y5 receptor‐specific antagonist did not affect responses to any agonist tested in any preparation. In slices from mice, NPY was without effect on evoked potentials or in either of the two slice seizure models. In vivo, intrahippocampal injections of Y2‐ or Y5‐preferring agonists inhibited seizures caused by intrahippocampal kainate, but again the Y5 agonist effects were insensitive to a Y5 antagonist. Neither Y2‐ nor Y5‐preferring agonists affected kainate seizures in mice. A Y5‐specific antagonist did not displace the binding of two different NPY ligands in WT or mice, whereas all NPY binding was eliminated in the mouse. Thus, we show that Y2 receptors alone mediate all the anti‐excitatory actions of NPY seen in the hippocampus, whereas our findings do not support a role for Y5 receptors either in vitro or in vivo. The results suggest that agonists targeting the Y2 receptor may be useful anticonvulsants.

PYY3-36 as an anti-obesity drug target.

The neuropeptide Y (NPY)/peptide YY (PYY) system has been implicated in the physiology of obesity for several decades. More recently, Batterham et al. 2002 ignited enormous interest in PYY3‐36, an endogenous Y2‐receptor agonist, as a promising anti‐obesity compound. Despite this interest, there have been remarkably few subsequent reports reproducing or extending the initial findings, while at the same time studies finding no anti‐obesity effects have surfaced. Out of 41 different rodent studies conducted (in 16 independent labs worldwide), 33 (83%) were unable to reproduce the reported effects and obtained no change or sometimes increased food intake, despite use of the same experimental conditions (i.e. adaptation protocols, routes of drug administration and doses, rodent strains, diets, drug vendors, light cycles, room temperatures). Among studies by authors in the original study, procedural caveats are reported under which positive effects may be obtained. Currently, data speak against a sustained decrease in food intake, body fat, or body weight gain following PYY3‐36 administration and make the previously suggested role of the hypothalamic melanocortin system unlikely as is the existence of PYY deficiency in human obesity. We review the studies that are in the public domain which support or challenge PYY3‐36 as a potential anti‐obesity target.

Epitope mapping of the Dermatophagoides pteronyssinus house dust mite major allergen Der p II using overlapping synthetic peptides

Fourteen synthetic peptides of 15 amino acid residues length, overlapping by five residues and spanning the entire sequence of the major allergen Der p II from the house dust mite Dermatophagoides pteronyssinus were synthesized. These peptides were coupled to CNBr-activated Sepharose-4B and used as solid-phase antigens in epitope mapping studies using human IgE antisera. These antibodies bound predominantly to the peptide comprising residues 65-78, the binding of which was inhibited by native Der p II. In addition these antisera bound, to a lesser extent, to the peptide that comprised residues 1-15, which binding was not inhibited by native Der p II. Thus, we found one sequential epitope for a number of IgE sera.

Visfatin/PBEF/Nampt : structure, regulation and potential function of a novel adipokine

Over the last few years, it has become obvious that obesity and insulin resistance are linked by a variety of proteins secreted by adipocytes. Visfatin/PBEF (pre-B-cell colony-enhancing factor) has recently been identified as a novel adipokine with insulin-mimetic effects. Furthermore, an enzymatic function has been reported that reveals visfatin/PBEF as Nampt (nicotinamide phosphoribosyltransferase; EC 2.4.2.12.). Moreover, reports on the structure and hormonal regulation of visfatin/PBEF/Nampt have given further insights into its potential physiological role. The present review summarizes studies on visfatin/PBEF/Nampt as a novel adipokine.

In vitro and in vivo evaluation of a 99mTc(I)-labeled bombesin analogue for imaging of gastrin releasing peptide receptor-positive tumors

A new radiolabeled bombesin analogue, [99mTc(I)-PADA-AVA]bombesin (7-14), was synthesized and in vitro and in vivo characterized. High affinity and rapid internalization were obtained in binding assays. A specific binding towards gastrin releasing peptide receptors-positive tissues, pancreas and tumor, was observed in CD-1 nu/nu mice bearing PC-3 prostate adenocarcinoma xenografts. We therefore conclude that [99mTc(I)-PADA-AVA]bombesin (7-14) might have promising characteristics for applications in nuclear medicine, namely for diagnosis of GRP receptor overexpressing tumors.