Pancreatic polypeptide enhances colonic muscle contraction and fecal output through neuropeptide Y Y4 receptor in mice.

Pancreatic polypeptide is released mainly from the pancreas, and is thought to be one of the major endogenous agonists of the neuropeptide Y Y(4) receptor. Pancreatic polypeptide has been shown to stimulate colonic muscle contraction, but whether pancreatic polypeptide has in vivo functional activity with respect to colonic transit is unclear. The present report investigated the effects of pancreatic polypeptide on fecal output as an index of colonic transit as well as intestinal motor activity, using wild-type (WT) and neuropeptide Y Y(4) receptor-deficient (KO) mice. Peripheral administration of pancreatic polypeptide increased fecal weight and caused diarrhea in WT mice in a dose-dependent manner (0.01-3mg/kg s.c.). Pancreatic polypeptide-induced increases in fecal weight and diarrhea completely disappeared in KO mice, while basal fecal weights did not differ between WT and KO mice. In longitudinal and circular muscles of mouse isolated colon, pancreatic polypeptide (0.01-1 microM) increased basal tone and frequency of spontaneous contraction in WT mice, but not in KO mice. Atropine did not affect pancreatic polypeptide-induced fecal output or increase in colonic muscle tone, indicating that the actions of pancreatic polypeptide are not mediated through cholinergic mechanisms. The present findings demonstrate that pancreatic polypeptide enhances colonic contractile activity and fecal output through neuropeptide Y Y(4) receptor, and a neuropeptide Y Y(4) receptor agonist might offer a novel therapeutic approach to ameliorate constipation.

Identification of MK-1925: a selective, orally active and brain-penetrable opioid receptor-like 1 (ORL1) antagonist.

Structure-activity relationship studies directed toward improving the metabolic stability of compound 1 resulted in the identification of 3-[5-(3,5-difluorophenyl)-3-({[(1S,3R)-3-fluorocyclopentyl]amino}methyl)-4-methyl-1H-pyrazol-1-yl]propanenitrile 39 (MK-1925) as a selective, orally available and brain-penetrable opioid receptor-like 1 (ORL1) antagonist. The compound also showed in vivo efficacy after oral dosing. Therefore, compound 39 was selected to undergo further studies as a clinical candidate.

Novel orally active NPY Y5 receptor antagonists: Synthesis and structure-activity relationship of spiroindoline class compounds.

Spiroindoline urea derivatives, designed to act as NPY Y5 receptor antagonists, were synthesized and their structure-activity relationships were investigated. Of these derivatives, compound 3a showed good Y5 binding affinity with favorable pharmacokinetic properties. Compound 3a significantly inhibited bPP Y5 agonist-induced food intake in rats, and suppressed body weight gain in DIO mice.

2-Cyclohexylcarbonylbenzimidazoles as potent, orally available and brain-penetrable opioid receptor-like 1 (ORL1) antagonists.

The synthesis and biological evaluation of new potent opioid receptor-like 1 (ORL1) antagonists are presented. Conversion of the thioether linkage of the prototype [It is reported prior to this communication as a consecutive series.: Kobayashi, K.; Kato, T.; Yamamoto, I.; Shimizu, A.; Mizutani, S.; Asai, M.; Kawamoto, H.; Ito, S.; Yoshizumi, T.; Hirayama, M.; Ozaki, S.; Ohta, H.; Okamoto, O. Bioorg. Med. Chem. Lett., in press] to the carbonyl linker effectively reduces susceptibility to P-glycoprotein (P-gp) efflux. This finding led to the identification of 2-cyclohexylcarbonylbenzimizole analogue 7c, which exhibited potent ORL1 activity, excellent selectivity over other receptors and ion channels, and poor susceptibility to P-gp. Compound 7c also showed satisfactory pharmacokinetic profiles and brain penetrability in laboratory animals. Furthermore, 7c showed good in vivo antagonism. Hence, 7c was selected as a clinical candidate for a brain-penetrable ORL1 antagonist.

Up-regulation of protease-activated receptor-1 in diabetic glomerulosclerosis.

Patients with diabetes are under a hypercoagulable state leading to generation of thrombin. It is not known whether thrombin plays a role in the progression of diabetic nephropathy. We analyzed gene expression of two thrombin receptors, protease-activated receptor-1 (PAR-1) and PAR-4 in the kidney of diabetic db/db mice. Mice developed hyperglycemia from 7 to 10 weeks of age and showed renal abnormalities such as mesangial expansion and urinary albumin excretion at 10 weeks of age. PAR-1 mRNA was up-regulated in isolated glomeruli in db/db mice compared with age-matched db/m littermates, but PAR-4 mRNA was not. In situ hybridization studies showed that PAR-1 mRNA was detected mainly at the glomerulus, and that intensive signals were observed in mesangial cells and podocytes. The up-regulation of PAR-1 in glomeruli in diabetic mice may play a role in the progression of glomerulosclerosis and abnormal urinary albumin excretion in diabetic nephropathy.

A novel class of cycloalkano[b]pyridines as potent and orally active opioid receptor-like 1 antagonists with minimal binding affinity to the hERG K+ channel.

A series of compounds based on 7-{[4-(2-methylphenyl)piperidin-1-yl]methyl}-6,7,8,9-tetrahydro-5 H-cyclohepta[ b]pyridine-9-ol ( (-)-8b), a potent and selective opioid receptor-like 1 (ORL1) antagonist, was prepared and evaluated using structure-activity relationship studies with the aim of removing its affinity to human ether-a-go-go related gene (hERG) K (+) channel. From these studies, 10l was identified as an optimized structure with respect to ORL1 antagonist activity, and affinity to the hERG K (+)channel. Furthermore, 10l showed good in vivo antagonism with a wide therapeutic index in regards to adverse cardiovascular effects.

A neuropeptide Y Y5 antagonist selectively ameliorates body weight gain and associated parameters in diet-induced obese mice.

Neuropeptide Y (NPY) is thought to have a major role in the physiological control of energy homeostasis. Among five NPY receptors described, the NPY Y5 receptor (Y5R) is a prime candidate to mediate some of the effects of NPY on energy homeostasis, although its role in physiologically relevant rodent obesity models remains poorly defined. We examined the effect of a potent and highly selective Y5R antagonist in rodent obesity and dietary models. The Y5R antagonist selectively ameliorated diet-induced obesity (DIO) in rodents by suppressing body weight gain and adiposity while improving the DIO-associated hyperinsulinemia. The compound did not affect the body weight of lean mice fed a regular diet or genetically obese leptin receptor-deficient mice or rats, despite similarly high brain Y5R receptor occupancy. The Y5R antagonist acts in a mechanism-based manner, as the compound did not affect DIO of Y5R-deficient mice. These results indicate that Y5R is involved in the regulation and development of DIO and suggest utility for Y5R antagonists in the treatment of obesity.

The functional shift of endothelin receptor subtypes in dogs with heart failure produced by rapid ventricular pacing.

To clarify the functional role of endothelin-A/endothelin- B (ETA/ETB) receptors in congestive heart failure (CHF), we examined the effects of a non-selective endothelin receptor agonist, endothelin-1 (ET-1), and a selective ETB receptor agonist, sarafotoxin S6c. CHF was induced in dogs by rapid ventricular pacing and resulted in decreased left ventricular dp/dtmax, decreased cardiac output and increased pulmonary vascular resistance. Sarafotoxin S6c (0.3 nmol/kg) resulted in decreased left ventricular dp/dtmax (-26 +/- 2%), decreased cardiac output (-47 +/- 3%) and increased pulmonary vascular resistance (+48 +/- 10%) in dogs without CHF. The effects of sarafotoxin S6c were attenuated in dogs with CHF (-12 +/- 5% in left ventricular dp/dtmax, -19 +/- 5% in cardiac output and +7 +/- 5% in pulmonary vascular resistance). In contrast, ET-1 (0.5 nmol/kg) had no effect on left ventricular dp/dtmax in dogs without CHF and increased left ventricular dp/dtmax by 16 +/- 3% in dogs with CHF. These data indicate that reduced cardiac contractile and pulmonary vasoconstrictor responses via the ETB receptor are attenuated and that responses mediated by the ETA receptor are more prominent in the context of CHF. This suggests a functional shift of endothelin receptor subtypes in CHF.

Characterization of neuropeptide Y (NPY) Y5 receptor-mediated obesity in mice: chronic intracerebroventricular infusion of D-Trp(34)NPY.

To clarify the role of the neuropeptide Y (NPY) Y5 receptor subtype in energy homeostasis, the effect of the intracerebroventricular infusion of a selective Y5 agonist, D-Trp(34)NPY, was investigated in C57BL/6J mice. Intracerebroventricular infusion of D-Trp(34)NPY (5 and 10 microg/d) produced hyperphagia and body weight gain, accompanied by increased adipose tissue weight, hypercholesterolemia, hyperinsulinemia, and hyperleptinemia. Oral administration of a selective Y5 antagonist at a dose of 100 mg/kg twice a day completely suppressed all of these D-Trp(34)NPY-induced changes, indicating that chronic activation of the Y5 receptor produces hyperphagia and obesity. In addition, D-Trp(34)NPY still resulted in an increase in adipose tissue weight accompanied by hyperleptinemia and hypercholesterolemia, although D-Trp(34)NPY-induced food intake was restricted by pair-feeding. Under the pair-fed condition, D-Trp(34)NPY decreased hormone-sensitive lipase activity in white adipose tissue and uncoupling protein-1 mRNA expression in brown adipose tissue. These findings indicate that Y5-mediated obesity may involve metabolic changes, such as decreased lipolysis and thermogenesis, as well as hyperphagia. Therefore, the Y5 receptor can play a key role in regulating energy homeostasis.

Structure-Activity relationships of 2-substituted 5,7-Diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acids as a novel class of endothelin receptor antagonists.

Synthesis and structure-activity relationships of 2-substituted-5,7-diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acids, a novel class of endothelin receptor antagonists, were described. Derivatization of a lead structure 1 (IC(50)=2.4nM, 170-fold selectivity) by incorporating a substituent such as an alkyl, alkoxy, alkylthio, or alkylamino group into the 2-position of the cyclopenteno[1,2-b]pyridine skeleton was achieved via the key intermediate 8. Introduction of an alkyl group led to the identification of potent ET(A)/ET(B) mixed receptor antagonists, a butyl (2d: IC(50)=0.21nM, 52-fold selectivity) and an isobutyl (2f: IC(50)=0.32nM, 26-fold selectivity) analogue. In contrast, installment of a primary amino group resulted in ET(A) selective antagonists, a propylamino 2p (IC(50)=0.12nM, 520-fold selectivity) and an isopropylamino 2q (IC(50)=0.10nM, 420-fold selectivity) analogue. These results suggested that a substituent at the 2-position of the 5,7-diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acids played a key role in the binding affinity for both ET(A) and ET(B) receptors.

6-Carboxy-5,7-diarylcyclopenteno[1,2-b]pyridine derivatives: a novel class of endothelin receptor antagonists.

Compounds (2-5) with a 6-carboxy-5,7-diarylcyclopentenopyridine skeleton were designed, synthesized, and identified as a new class of potent non-peptide endothelin receptor antagonists. The regio-isomer 2 was found to show potent inhibitory activity with an IC(50) value of 2.4 nM against (125)I-labeled ET-1 binding to human ET(A) receptors and a 170-fold selectivity for ET(A) over ET(B) receptors. Furthermore, 2 displayed more potent in vivo activity than did the indan-type compound 1 in a mouse ET-1 induced lethality model, suggesting the potential of 2 as a new lead structure. Derivatization on substituted phenyl groups at the 5- and 7-positions of 2 revealed that a 3,4-methylenedioxyphenyl group at the 5-position and a 4-methoxyphenyl group at the 7-position were optimal for binding affinity. Further derivatization of 2 by incorporating a substituent into the 2-position of the 4-methoxyphenyl group led to the identification of a more potent ET(A) selective antagonist 2p with an IC(50) value of 0.87 nM for ET(A) receptors and a 470-fold selectivity. In addition, 2p showed highly potent in vivo efficacy (AD(50): 0.04 mg/kg) in the lethality model.

Blockade of body weight gain and plasma corticosterone levels in Zucker fatty rats using an orally active neuropeptide Y Y1 antagonist.

1. An experiment was conducted to examine whether a potent, orally active and highly selective neuropeptide Y Y1 receptor antagonist attenuates hyperphagia and obesity in genetically obese Zucker fatty rats. 2. Oral administration of the Y1 antagonist (30 and 100 mg x kg(-1), once daily for 2 weeks) significantly suppressed the daily food intake and body weight gain in Zucker fatty rats accompanied with a reduction of fat cell size and plasma corticosterone levels. 3. Despite the fact that food intake was gradually returned to near the control level, the body weight of the treated animals remained significantly less when compared to that of the controls for the duration of the treatment. 4. These results suggest that the Y1 receptor, at least in part, participate in pathophysiological feeding and/or fat accumulation observed in Zucker fatty rats. Y1 antagonists might be useful for the treatment of obesity.