Ovarian cancer derived PKR1 positive exosomes promote angiogenesis by promoting migration and tube formation in vitro.

Cancer cell derived exosomes play important roles in cancer progression and modulation of the tumour microenvironment. This study aims to investigate the role of prokineticin receptor 1 (PKR1) positive exosomes on angiogenesis. In the present study, PKR1 expression in tumour samples from ovarian cancer patients were examined firstly. Then, two ovarian cancer cell lines, namely A2780 and HO-8910 cells, were used to isolate and obtain the PKR1 positive exosomes from the serum free medium. The function analysis of PKR1 positive exosomes on angiogenesis was conducted by cell proliferation and migration assay, tube formation analysis, and tumour volume assay. The results showed that PKR1 expression was down regulated in tumour samples of ovarian cancer patients compared with adjacent normal tissues. The intracellular expression of PKR1 could be detected in A2780 and HO-8910 cells. And, the isolated exosomes from the serum free medium were confirmed by transmission electron microscopic and NTA analysis, as well as the co-presence of PKR1 with exosome marker CD63. The function analysis of PKR1 positive exosomes on angiogenesis demonstrated the uptake of PKR1 positive exosomes by human umbilical vein endothelial cells through immunofluorescence staining. The angiogenesis assays in vitro indicated that PKR1 positive exosomes promoted migration and tube formation of HUVECs but not proliferation. The endogenous PKR1 was also verified to help to enhance migration and promote tube formation of vascular endothelial cells, which might involved in the phosphorylation of STAT3. Additionally, The tumour volume from exosomes treated A2780 tumour-bearing mice was significantly increased compared with the control group, accompanied with the induced PKR1 expression and phosphorylation of STAT3 level. SIGNIFICANCE OF THE STUDY: This study proved the important role of PKR1 positive exosomes released from ovarian cancer cells on promoting angiogenesis. The data indicated that PKR1 derived from ovarian cancer cells could act as an important tumour associated antigen and biomolecular factor for cellular communication in tumour microenvironment.

Silencing PROK2 Inhibits Invasion of Human Cervical Cancer Cells by Targeting MMP15 Expression.

Cervical cancer is the second most frequent type of gynecologic cancer worldwide. Prokineticin 2 (PROK2) is reported to be involved in tumor progression in some malignant tumors. However, the role of PROK2 in the development of cervical cancer remains unknown. Our results indicate that PROK2 is overexpressed in the human cervical cancer. Cervical cancer patients with high PROK2 expression have a shorter overall survival rate (OS) and disease-free survival rate (DFS). PROK2 acts as a potential biomarker for predicting OS and DFS of cervical cancer patients. We further show that PROK2 is important factor for oncogenic migration and invasion in human cervical cancer cells. Knockdown PROK2 significantly inhibited cell migration, invasion, and MMP15 protein expression in HeLa cells. High expression of MMP15 is confirmed in the human cervical cancer, is significantly associated with the shorter overall survival rate (OS) and is correlated with PROK2 expression. Overexpression of PROK2 using PROK2 plasmid significantly reverses the function of knockdown PROK2, and further upregulates MMP15 expression, migration and invasion of human cervical cancer cells. In conclusion, our findings are the first to demonstrate the role of PROK2 as a novel and potential biomarker for clinical use, and reveal the oncogenic functions of PROK2 as therapeutic target for cervical cancer.

Prokineticin 2 antagonist, PKRA7 suppresses arthritis in mice with collagen-induced arthritis.

BACKGROUND: Prokineticin 2 (PK2) expression is upregulated in mice with collagen-induced arthritis (CIA), an animal model of rheumatoid arthritis. The purpose of our study was to investigate the effects of PK2 inhibition on CIA. METHODS: PK2, prokineticin receptor (PKR) 1, and PKR2 mRNA transcripts in the joints of CIA mice were measured by real-time PCR on Days 21, 28, and 35 (n = 15/day). Localization of PKR1 and PKR2 proteins was examined immunohistochemically. PKRA7, a PK2 antagonist, was administered intraperitoneally for 2 weeks to CIA mice, and the severity of arthritis was compared between treated (n = 12) and untreated (n = 12) mice. The gene expression levels of inflammatory cytokines IL-1ß, IL-6, TNF-α, and VEGF were also measured by real-time PCR and compared between treated (n = 6) and untreated (n = 6) CIA mice. The data was statistically analyzed, and P values of less than 0.05 were considered significant. RESULTS: In the thickened synovial membrane, PKR1 protein was expressed in infiltrating neutrophils, while PKR2 expression was found in macrophage-like mononuclear cells. PK2 gene expression was significantly more pronounced on Days 28 and 35 than on Day 21 (2.15 and 2.03 versus 1.00, P = 0.0311 and 0.0247; Dunn's multiple comparison). PKR2 gene expression levels were significantly higher on Days 28 and 35 compared to Day 21 (25.4 and 39.3 versus 1.0, P = 0.002 and < 0.0001; Dunn's multiple comparison). Administration of PKRA7 suppressed the severity of arthritis (P < 0.001; two-way analysis of variance). A gene expression analysis of inflammatory cytokines revealed significantly reduced IL-1ß and lL-6 expression in the joints of PKRA7-treated mice compared to untreated mice (0.1 versus 1.0, P = 0.0043 and 0.04 versus 1.0, P = 0.0022, respectively; Mann-Whitney test). CONCLUSIONS: PK2 inhibition suppressed arthritis in mice with CIA.

Gut Hormone Suppression Increases Food Intake After Esophagectomy With Gastric Conduit Reconstruction.

OBJECTIVES: To characterize the gut hormone profile and determine the effect of satiety gut hormone blockade on food intake in disease-free postesophagectomy patients. BACKGROUND: Improved oncologic outcomes for esophageal cancer have resulted in increased survivorship and a focus on health-related quality of life. Anorexia and early satiety are common, but putative causative factors, in particular the gut-brain hormonal axis, have not been systematically studied. METHODS: In a double-blind, placebo-controlled, randomized crossover study, disease-free patients at least 1 year postresection and gastric conduit reconstruction received either 1 mL 0.9% saline or 1 mL (100 µg) octreotide acetate subcutaneously followed by a standardized ad libitum meal on each of two assessments. Fasting and postprandial plasma glucagon-like peptide 1 (GLP-1), peptide YY (PYY), and ghrelin immunoreactivity were measured. Gut hormone responses and calorie intake postsaline versus octreotide were compared between experimental and control groups. RESULTS: Eighteen subjects [esophagectomy (ES), n = 10, 2.4 ±â€Š0.75 years postresection; and unoperated control subjects, n = 8] were studied. ES demonstrated significant weight loss at 3, 6, 12, and 24 months postoperatively (all P < 0.05). Ghrelin levels were similar (P = 0.58) for both groups, but postprandial GLP-1 and PYY responses were significantly (P < 0.001) greater among ES as compared with controls. After octreotide, ad libitum calorie intake increased among ES (1.5 ±â€Š0.2 fold-change, P = 0.02) but not controls (1.1 ±â€Š0.1 fold-change, P = 0.30). CONCLUSIONS: ES demonstrated an exaggerated postprandial satiety gut hormone response that was attenuated by octreotide, thus identifying a potential therapeutic target to modulate in the ES patient with early satiety.

Bv8 regulates myeloid-cell-dependent tumour angiogenesis.

Bone-marrow-derived cells facilitate tumour angiogenesis, but the molecular mechanisms of this facilitation are incompletely understood. We have previously shown that the related EG-VEGF and Bv8 proteins, also known as prokineticin 1 (Prok1) and prokineticin 2 (Prok2), promote both tissue-specific angiogenesis and haematopoietic cell mobilization. Unlike EG-VEGF, Bv8 is expressed in the bone marrow. Here we show that implantation of tumour cells in mice resulted in upregulation of Bv8 in CD11b+Gr1+ myeloid cells. We identified granulocyte colony-stimulating factor as a major positive regulator of Bv8 expression. Anti-Bv8 antibodies reduced CD11b+Gr1+ cell mobilization elicited by granulocyte colony-stimulating factor. Adenoviral delivery of Bv8 into tumours was shown to promote angiogenesis. Anti-Bv8 antibodies inhibited growth of several tumours in mice and suppressed angiogenesis. Anti-Bv8 treatment also reduced CD11b+Gr1+ cells, both in peripheral blood and in tumours. The effects of anti-Bv8 antibodies were additive to those of anti-Vegf antibodies or cytotoxic chemotherapy. Thus, Bv8 modulates mobilization of CD11b+Gr1+ cells from the bone marrow during tumour development and also promotes angiogenesis locally.

Inhibition of FABP6 Reduces Tumor Cell Invasion and Angiogenesis through the Decrease in MMP-2 and VEGF in Human Glioblastoma Cells.

Malignant glioma is one of the most lethal cancers with rapid progression, high recurrence, and poor prognosis in the central nervous system. Fatty acid-binding protein 6 (FABP6) is a bile acid carrier protein that is overexpressed in colorectal cancer. This study aimed to assess the involvement of FABP6 expression in the progression of malignant glioma. Immunohistochemical analysis revealed that FABP6 expression was higher in glioma than in normal brain tissue. After the knockdown of FABP6, a decrease in the migration and invasion abilities of glioma cells was observed. The phosphorylation of the myosin light chain was inhibited, which may be associated with migration ability. Moreover, expression levels of invasion-related proteins, matrix metalloproteinase-2 (MMP-2) and cathepsin B, were reduced. Furthermore, tube formation was inhibited in the human umbilical vein endothelial cells with a decreased concentration of vascular endothelial growth factor (VEGF) in the conditioned medium after the knockdown of FABP6. The phosphorylation of the extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p65 were also decreased after FABP6 reduction. Finally, the bioluminescent images and immunostaining of MMP-2, cluster of differentiation 31 (CD31), and the VEGF receptor 1 (VEGFR1) revealed attenuated tumor progression in the combination of the FABP6-knocked-down and temozolomide (TMZ)-treated group in an orthotopic xenograft mouse tumor model. This is the first study that revealed the impact of FABP6 on the invasion, angiogenesis, and progression of glioma. The results of this study show that FABP6 may be a potential therapeutic target combined with TMZ for malignant gliomas.

Prokineticin Receptor Inhibition With PC1 Protects Mouse Primary Sensory Neurons From Neurotoxic Effects of Chemotherapeutic Drugs in vitro.

Neurotoxicity is a common side effect of chemotherapeutics that often leads to the development of chemotherapy-induced peripheral neuropathy (CIPN). The peptide Prokineticin 2 (PK2) has a key role in experimental models of CIPN and can be considered an insult-inducible endangering mediator. Since primary afferent sensory neurons are highly sensitive to anticancer drugs, giving rise to dysesthesias, the aim of our study was to evaluate the alterations induced by vincristine (VCR) and bortezomib (BTZ) exposure in sensory neuron cultures and the possible preventive effect of blocking PK2 signaling. Both VCR and BTZ induced a concentration-dependent reduction of total neurite length that was prevented by the PK receptor antagonist PC1. Antagonizing the PK system also reduced the upregulation of PK2, PK-R1, TLR4, IL-6, and IL-10 expression induced by chemotherapeutic drugs. In conclusion, inhibition of PK signaling with PC1 prevented the neurotoxic effects of chemotherapeutics, suggesting a promising strategy for neuroprotective therapies against the sensory neuron damage induced by exposure to these drugs.

Heat-stable enterotoxin of Escherichia coli (STa) can stimulate duodenal HCO3(-) secretion via a novel GC-C- and CFTR-independent pathway.

The heat-stable enterotoxin of Escherichia coli (STa) is a potent stimulant of intestinal chloride and bicarbonate secretion. Guanylyl cyclase C (GC-C) has been shown to be the primary receptor involved in mediating this response. However, numerous studies have suggested the existence of an alternative STa-binding receptor. The aims of this study were to determine whether a non-GC-C receptor exists for STa and what is the functional relevance of this for intestinal bicarbonate secretion in mice. (125)I-STa-binding experiments were performed with intestinal mucosae from GC-C knockout (KO) and wild type (WT) mice. Subsequently, the functional relevance of an alternative STa-binding receptor was explored by examining STa-, uroguanylin-, and guanylin-stimulated duodenal bicarbonate secretion (DBS) in GC-C KO mice in vitro and in vivo. Significant (125)I-STa-binding occurred in the proximal small intestines of GC-C KO and WT mice. Analysis of binding coefficients and pH dependence showed that (125)I-STa-binding in GC-C KO mice involved a receptor distinct from that of WT mice. Functionally, STa, uroguanylin, and guanylin all stimulated a significant increase in DBS in GC-C KO mice. Uroguanylin- and guanylin-stimulated DBS were significantly inhibited by glibenclamide, but not by 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS). However, STa-stimulated DBS was unaffected by glibenclamide but inhibited by DIDS. Taken together, our results suggest that alternative, non-GC-C, receptors likely exist for STa, uroguanylin, and guanylin in the intestines of mice. While uroguanylin- and guanylin-stimulated DBS are cystic fibrosis transmembrane conductance regulator (CFTR) dependent, STa-stimulated DBS is CFTR independent. Further understanding of this alternative receptor and its signaling pathway may provide important insights into rectification of intestinal bicarbonate secretion in cystic fibrosis.

The obesity pipeline: current strategies in the development of anti-obesity drugs.

This review provides a summary of currently available pharmaceutical therapies for the treatment of obesity, along with an overview of the pipeline of products currently in development, and the key mechanisms on which the major development candidates are based. In particular, the recent increase in understanding of the role of gut peptides in energy homeostasis is highlighted as a promising source of potential future obesity therapies.

New roles for prokineticin 2 in feeding behavior, insulin resistance and type 2 diabetes: Studies in mice and humans.

OBJECTIVE: Prokineticin 2 (PROK2) is a hypothalamic neuropeptide that plays a critical role in the rhythmicity of physiological functions and inhibits food intake. PROK2 is also expressed in the main olfactory bulb (MOB) as an essential factor for neuro-and morphogenesis. Since the MOB was shown to be strongly involved in eating behavior, we hypothesized that PROK2 could be a new target in the regulation of food intake and energy homeostasis, through its effects in the MOB. We also asked whether PROK2 could be associated with the pathophysiology of obesity, the metabolic syndrome (MetS), and type 2 diabetes (T2D) in humans. METHODS: We assessed in wild type mice whether the expression of Prok2 in the MOB is dependent on the nutritional status. We measured the effect of human recombinant PROK2 (rPROK2) acute injection in the MOB on food intake and olfactory behavior. Then, using a lentivirus expressing Prok2-shRNA, we studied the effects of Prok2 underexpression in the MOB on feeding behavior and glucose metabolism. Metabolic parameters and meal pattern were determined using calorimetric cages. In vivo 2-deoxyglucose uptake measurements were performed in mice after intraperitoneally insulin injection. Plasmatic PROK2 dosages and genetic associations studies were carried out respectively on 148 and more than 4000 participants from the D.E.S.I.R. (Data from an Epidemiologic Study on the Insulin Resistance Syndrome) cohort. RESULTS: Our findings showed that fasting in mice reduced Prok2 expression in the MOB. Acute injection of rPROK2 in the MOB significantly decreased food intake whereas Prok2-shRNA injection resulted in a higher dietary consumption characterized by increased feeding frequency and decreased meal size. Additionally, Prok2 underexpression in the MOB induced insulin resistance compared to scrambled shRNA-injected mice. In the human D.E.S.I.R. cohort, we found a significantly lower mean concentration of plasma PROK2 in people with T2D than in those with normoglycemia. Interestingly, this decrease was no longer significant when adjusted for Body Mass Index (BMI) or calorie intake, suggesting that the association between plasma PROK2 and diabetes is mediated, at least partly, by BMI and feeding behavior in humans. Moreover, common Single Nucleotide Polymorphisms (SNPs) in PROK2 gene were genotyped and associated with incident T2D or impaired fasting glycemia (IFG), MetS, and obesity. CONCLUSIONS: Our data highlight PROK2 as a new target in the MOB that links olfaction with eating behavior and energy homeostasis. In humans, plasma PROK2 is negatively correlated with T2D, BMI, and energy intake, and PROK2 genetic variants are associated with incident hyperglycemia (T2D/IFG), the MetS and obesity.

Increased endothelin-1-mediated vasoconstrictor tone in human obesity: effects of gut hormones.

The heavy impact of obesity on the development and progression of cardiovascular disease has sparked sustained efforts to uncover the mechanisms linking excess adiposity to vascular dysfunction. Impaired vasodilator reactivity has been recognized as an early hemodynamic abnormality in obese patients, but also increased vasoconstrictor tone importantly contributes to their vascular damage. In particular, upregulation of the endothelin (ET)-1 system, consistently reported in these patients, might accelerate atherosclerosis and its complication, given the pro-inflammatory and mitogenic properties of ET-1. In recent years, a number of gut hormones, in addition to their role as modulators of food intake, energy balance, glucose and lipid metabolism, and insulin secretion and action, have demonstrated favorable vascular actions. They increase the bioavailability of vasodilator mediators like nitric oxide, but they have also been shown to inhibit the ET-1 system. These features make gut hormones promising tools for targeting both the metabolic and cardiovascular complications of obesity, a view supported by recent large-scale clinical trials indicating that novel drugs for type 2 diabetes with cardiovascular potential may translate into clinically significant advantages. Therefore, there is real hope that better understanding of the properties of gut-derived substances might provide more effective therapies for the obesity-related cardiometabolic syndrome.

Gut hormone polyagonists for the treatment of type 2 diabetes.

Chemical derivatives of the gut-derived peptide hormone glucagon-like peptide 1 (GLP-1) are among the best-in-class pharmacotherapies to treat obesity and type 2 diabetes. However, GLP-1 analogs have modest weight lowering capacity, in the range of 5-10%, and the therapeutic window is hampered by dose-dependent side effects. Over the last few years, a new concept has emerged: combining the beneficial effects of several key metabolic hormones into a single molecular entity. Several unimolecular GLP-1-based polyagonists have shown superior metabolic action compared to GLP-1 monotherapies. In this review article, we highlight the history of polyagonists targeting the receptors for GLP-1, GIP and glucagon, and discuss recent progress in expanding of this concept to now allow targeted delivery of nuclear hormones via GLP-1 and other gut hormones, as a novel approach towards more personalized pharmacotherapies.

Identification and Investigation of Novel Binding Fragments in the Fatty Acid Binding Protein 6 (FABP6).

Fatty acid binding protein 6 (FABP6) is a potential drug discovery target, which, if inhibited, may have a therapeutic benefit for the treatment of diabetes. Currently, there are no published inhibitors of FABP6, and with the target believed to be amenable to fragment-based drug discovery, a structurally enabled program was initiated. This program successfully identified fragment hits using the surface plasmon resonance (SPR) platform. Several hits were validated with SAR and were found to be displaced by the natural ligand taurocholate. We report the first crystal structure of human FABP6 in the unbound form, in complex with cholate, and with one of the key fragments.

Prokineticin 2 facilitates mechanical allodynia induced by α,ß-methylene ATP in rats.

Prokineticin 2 (PK2), a new chemokine, causes mechanical hypersensitivity in the rat hind paw, but little is known about the molecular mechanism. Here, we have found that ionotropic P2X receptor is essential to mechanical allodynia induced by PK2. First, intraplantar injection of high dose (3 or 10 pmol) of PK2 significantly increased paw withdrawal response frequency (%) to innocuous mechanical stimuli (mechanical allodynia). And the mechanical allodynia induced by PK2 was prevented by co-administration of TNP-ATP, a selective P2X receptor antagonist. Second, although low dose (0.3 or 1 pmol) of PK2 itself did not produce an allodynic response, it significantly facilitated the mechanical allodynia evoked by intraplantar injection of α,ß-methylene ATP (α,ß-meATP). Third, PK2 concentration-dependently potentiated α,ß-meATP-activated currents in rat dorsal root ganglion (DRG) neurons. Finally, PK2 receptors and intracellular signal transduction were involved in PK2 potentiation of α,ß-meATP-induced mechanical allodynia and α,ß-meATP-activated currents, since the potentiation were blocked by PK2 receptor antagonist PKRA and selective PKC inhibitor GF 109203X. These results suggested that PK2 facilitated mechanical allodynia induced by α,ß-meATP through a mechanism involved in sensitization of cutaneous P2X receptors expressed by nociceptive nerve endings.

Gut hormones as peripheral anti obesity targets.

Many peptides are synthesised and released from the gastrointestinal tract. Whilst their roles in regulation of gastrointestinal function have been known for some time, it is now evident that they also influence eating behaviour and thus potential anti obesity targets. Peptide YY (PYY) is released post prandially from the gastrointestinal L-cells with glucagon-like peptide 1 (GLP-1) and oxyntomodulin. Following peripheral administration of PYY 3-36, the circulating form of PYY, to mouse, rat or human there is marked inhibition of food intake. PYY 3-36 is thought to mediate its actions through the NPY Y2 GPCR. Obese subjects have lower basal fasting PYY levels and have a smaller post prandial rise. However, obesity does not appear to be associated with resistance to PYY (as it is with leptin) and exogenous infusion of PYY 3-36 results in a reduction in food intake by 30% in an obese group and 31% in a lean group. GLP-1 or oxyntomodulin, products of the prepreglucagon gene, decrease food intake when administered either peripherally or directly into the CNS. In addition, both have been shown to decrease food intake in humans. These effects are thought to be mediated by the GLP-1 receptor. Ghrelin, a huger hormone produced by the stomach, increases in the circulation following a period of fasting. Administration of ghrelin either peripherally or directly into the CNS increases food intake and chronic administration leads to obesity. Further infusion into normal healthy volunteers increases both food intake and appetite. Ghrelin is thought to act through the growth hormone secretagogue receptor (GHS-R). Obesity is the current major cause of premature death in the UK, killing almost 1000 people a week. Worldwide its prevalence is accelerating. The administration of the naturally occurring gut hormone may offer a long-term therapeutic approach to weight control. Here we consider the therapeutic potential of some gut hormones, and the GPCR's through which they act, in the treatment of obesity.

Topical capsaicin pretreatment inhibits axon reflex vasodilatation caused by somatostatin and vasoactive intestinal polypeptide in human skin.

1 Wheal and flare reactions are described following intradermal injections of somatostatin, vasoactive intestinal polypeptide, substance P and histamine in normal human forearm skin. Bombesin failed to produce a significant wheal and flare.2 Pretreatment of skin with capsaicin in all cases dramatically inhibited the flare but not the wheal. This result is in accord with the hypothesis that capsaicin blocks the effector side of the axon reflex, perhaps by depleting nerve terminals of vasodilatory peptide(s).

Selective inhibition of neuropeptide Y Y1 receptors by BIBP3226 in rat and human epithelial preparations.

BIBP3226 (N2-(diphenylacetyl)-N-[4-hydroxyphenyl)methyl]-D-arginine amide) has been used to examine the presence of neuropeptide Y Y1 receptors in 3 gastrointestinal epithelial preparations, namely the rat jejunum and descending colon mucosae and a human colonic adenocarcinoma cell line. The selective Y1 receptor antagonist (1 microM BIBP3226) had no significant effect upon either peptide YY (PYY) responses or on electric field stimulated changes in electrogenic ion transport in rat jejunum mucosa. Partial inhibition of PYY responses was observed following BIBP3226 pretreatment of rat colon mucosal preparations in the presence and absence of tetrodotoxin. Responses to the Y1 selective agonist [Leu31,Pro34]neuropeptide Y ([Leu31, Pro34]NPY) in descending colon preparations were significantly attenuated by BIBP3226 (1 microM). The same concentration of antagonist abolished responses to PYY and [Leu31,Pro34]NPY but had no effect upon human pancreatic polypeptide (hPP) in monolayer cultures of the human adenocarcinoma cell line, Colony-6. Schild analysis of BIBP3226 antagonism of PYY responses in Colony-6 cells provided a pA2 value of 7.9 with a Hill slope of 1.03, indicating competitive antagonism at these epithelial Y1 receptors.

Apparent affinity and potency of BIBP3226, a non-peptide neuropeptide Y receptor antagonist, on purported neuropeptide Y Y1, Y2 and Y3 receptors.

The newly developed, purported non-peptide neuropeptide Y Y1 receptor antagonist BIBP3226 was evaluated for its potential effect on the recently characterized Y3 receptor subtype and for its apparent affinity in rat and human brain membrane binding assays using highly selective neuropeptide Y Y1 and Y2 radioligands. BIBP3226 potently blocked (pA2 = 7.36) the contractile effect of neuropeptide Y in the rabbit saphenous vein, a Y1 receptor bioassay and demonstrated nM affinity for Y1/[125I][Leu31,Pro34]peptide YY binding sites. In contrast, it failed to antagonize the biological effects of neuropeptide Y in the rat vas deferens (Y2) and rat colon (Y3) and did not significantly competed for Y2/[125I]peptide YY-(3-36) binding sites in rat and human brain homogenates. Taken together, the results demonstrate further the high potency and selectivity of BIBP3226 for the neuropeptide Y Y1 receptor by establishing its lack of antagonist activity on the Y3 subtype.

Effect of naloxone and antidepressants on hyperphagia produced by peptide YY.

Central injection of peptide YY (PYY) elicits a powerful feeding response with a short latency in satiated rats. Because of this effect, PYY has been implicated as a neurochemical signal in bulimia nervosa. Serotonin agonists and opioid antagonists induce anorectic effects upon feeding behavior in humans and animals. Therefore, to investigate a possible interaction between PYY-induced eating and these anorexigenic agents rats were given injections of either naloxone (100 micrograms/3 microliters, ICV, and 10 mg/kg, SC), fluoxetine (3-30 micrograms/3 microliters and 5-10 mg/kg, IP), or clomipramine (3-30 micrograms/3 microliters and 5-10 mg/kg, IP) prior to fourth ventricular injections of PYY (15 micrograms/18 microliters). Central and peripheral naloxone and IP but not central injections of fluoxetine blocked PYY-induced intake. Clomipramine had no effect. This suggests that PYY-stimulated feeding may require the action of endogenous opioids and may be inhibited by serotonergic function.

Suppression of peptide YY-induced hyperphagia by terbutaline.

Central administrations of neuropeptide Y and peptide YY (PYY) produce robust increases in food intake, and this response may be contingent upon the availability of insulin. In contrast, beta 2-adrenergic agonists decrease food intake, and this effect also appears to be dependent on circulating insulin. To investigate a possible interaction between PYY and beta 2-adrenergic function, rats were given systemic injections of terbutaline, a beta 2 agonist, at doses of 0, 5, 10, and 50 mg/kg prior to injections of 0.57 nmol PYY in the paraventricular nucleus of the hypothalamus. Terbutaline pretreatment significantly decreased feeding elicited by PYY in a dose-dependent fashion. This suggests that beta 2-adrenoreceptor activity is involved in PYY-induced feeding.