Non-peptide Agonist Research Articles

ORL1 Activation Mediates a Novel ORL1 Receptor Agonist SCH221510 Analgesia in Neuropathic Pain in Rats.

Opioid receptor like 1 (ORL1) receptor activation displayed an anti-nociceptive effect at spinal level for acute and neuropathic pain. SCH221510, an orally active non-peptide ORL1 agonist, was reported to be effective in treating neuropathic pain. The present study used ORL1 antagonist and siRNA to investigate that ORL1 activation mediates intrathecal SCH221510 analgesia in neuropathic pain induced by chronic constrictive injury (CCI) to rat sciatic nerve. Paw withdrawal latency and 50% mechanical threshold were measured for thermal and mechanical hypersensitivity in rats. CCI significantly decreased paw withdrawal latency and mechanical threshold. SCH221510 (3, 10, 30μg) or ORL1 antagonist ([Nphe1]nociceptin(1-13)NH2, 10μg) was intrathecally injected to test the behavioral effects on neuropathic pain. Intrathecal siRNA was started on 1day before CCI surgery and maintained for 7days. L4-L5 spinal cord ORL1 mRNA and protein were measured by real-time PCR and Western blot. The effect of intrathecal siRNA on SCH2210510 was tested in CCI rats on day 7. Intrathecal SCH221510 dose-dependently reduced thermal and mechanical hypersensitivity induced by CCI. [Nphe1]nociceptin(1-13)NH2 blocked SCH221510 analgesia in CCI rats. Intrathecal siRNA blocked ORL1 mRNA and protein increase induced by CCI. Intrathecal ORL1 siRNA did not change thermal and mechanical hypersensitivity induced by nerve injury. Intrathecal siRNA blocked SCH221510 analgesia in neuropathic pain at spinal level. Conclusively, ORL1 activation mediates SCH221510 analgesia in neuropathic pain at spinal level. The results warrant a potential clinically applicable drug in treating neuropathic pain.

Peptidergic control of the crop of the cabbage root fly, Delia radicum (L.) Diptera: Anthomyiidae): A role for myosuppressin

There is much interest in targeting neuropeptide signaling for the development of new and environmentally friendly insect control chemicals. In this study we have focused attention on the peptidergic control of the adult crop of Delia radicum (cabbage root fly), an important pest of brassicas in European agriculture. The dipteran crop is a muscular organ formed from the foregut of the digestive tract and plays a vital role in the processing of food in adult flies. We have shown using direct tissue profiling by MALDI-TOF mass spectrometry that the decapeptide myosuppressin (TDVDHVFLRFamide) is present in the crop nerve bundle and that application of this peptide to the crop potently inhibits the spontaneous contractions of the muscular lobes with an IC50 of 4.4 × 10−8 M. The delivery of myosuppressin either by oral administration or by injection had no significant detrimental effect on the adult fly. This failure to elicit a response is possibly due to the susceptibility of the peptide to degradative peptidases that cleave the parent peptide to inactive fragments. Indeed, we show that the crop of D. radicum is a source of neuropeptide-degrading endo- and amino-peptidases. In contrast, feeding benzethonium chloride, a non-peptide agonist of myosuppressin, reduced feeding rate and increased the rate of mortality of adult D. radicum. Current results are indicative of a key role for myosuppressin in the regulation of crop physiology and the results achieved during this project provide the basis for subsequent studies aimed at developing insecticidal molecules targeting the peptidergic control of feeding and food digestion in this pest species.

OWL833, an Orally Active Nonpeptide GLP-1 Receptor Agonist, Improves Glucose Tolerance by Increasing Insulin Secretion and Reduces Food Intake of Cynomolgus Monkeys

Activation of glucagon-like peptide-1 receptors (GLP-1R) is a promising approach for the treatment of type 2 diabetes mellitus (T2D), and several peptide analogues of GLP-1 have been successfully developed. Here we identified a new orally active non-peptide GLP-1R agonist, OWL833, and examined its efficacy in cynomolgus monkeys. The agonistic activity of OWL833 was evaluated by measuring cAMP accumulation in cells expressing mammal GLP-1Rs and other glucagon family receptors. In the cells expressing human or cynomolgus monkey GLP-1R, OWL833 promoted cAMP accumulation to the same level achieved by GLP-1, and its EC50 values for human and cynomolgus monkey GLP-1Rs were the same at 1.1 nmol/L. In contrast, OWL833 showed no stimulatory activity on human glucagon, GIP, and GLP-2 receptors. The predicted bioavailability and T1/2 of OWL833 in human based on rodent and non-rodent experimental data are 30% and ∼18 hour, respectively. After OWL833 followed by glucose was intravenously injected in cynomolgus monkeys, OWL833 decreased the blood glucose level via insulin secretion to the same extent as effective concentrations of exenatide, a GLP-1 peptide mimetic, in clinic. Doses of 0.and 0.1 mg/kg OWL833 given orally to cynomolgus monkeys reduced their food intake by 25% and 45%, respectively, as compared with vehicle group, and the effect on food intake was equal to that of 0.3 and 0.6 µg/kg subcutaneous injections of exenatide. No critical finding was observed in the subchronic toxicity studies in rats and cynomolgus monkeys. These findings demonstrate that OWL833 has full agonistic activity on human and cynomolgus GLP-1R and improves glucose tolerance by stimulating insulin secretion, and that it exhibits an anti-feeding activity similar to exenatide. In conclusion, OWL833 has potential as a once-daily, orally active, non-peptide GLP-1 receptor agonist. Disclosure T. Kawai: Employee; Self; Chugai Pharmaceutical Co., Ltd. F. Tanino: Employee; Self; Chugai Pharmaceutical Co., Ltd. M. Fukazawa: Employee; Self; Chugai Pharmaceutical Co., Ltd. K. Ogawa: Employee; Self; Chugai Pharmaceutical Co., Ltd. S. Nagao: Employee; Self; Chugai Pharmaceutical Co., Ltd. H. Yoshino: Employee; Self; Chugai Pharmaceutical Co., Ltd. S. Komatsu: Employee; Self; Chugai Pharmaceutical Co., Ltd. Y. Suzuki: Employee; Self; Chugai Pharmaceutical Co., Ltd. Y. Kawabe: Employee; Self; Chugai Pharmaceutical Co., Ltd..

Quinolones Modulate Ghrelin Receptor Signaling: Potential for a Novel Small Molecule Scaffold in the Treatment of Cachexia.

Cachexia is a metabolic wasting disorder characterized by progressive weight loss, muscle atrophy, fatigue, weakness, and appetite loss. Cachexia is associated with almost all major chronic illnesses including cancer, heart failure, obstructive pulmonary disease, and kidney disease and significantly impedes treatment outcome and therapy tolerance, reducing physical function and increasing mortality. Current cachexia treatments are limited and new pharmacological strategies are needed. Agonists for the growth hormone secretagogue (GHS-R1a), or ghrelin receptor, prospectively regulate the central regulation of appetite and growth hormone secretion, and therefore have tremendous potential as cachexia therapeutics. Non-peptide GHS-R1a agonists are of particular interest, especially given the high gastrointestinal degradation of peptide-based structures, including that of the endogenous ligand, ghrelin, which has a half-life of only 30 min. However, few compounds have been reported in the literature as non-peptide GHS-R1a agonists. In this paper, we investigate the in vitro potential of quinolone compounds to modulate the GHS-R1a in both transfected human cells and mouse hypothalamic cells. These chemically synthesized compounds demonstrate a promising potential as GHS-R1a agonists, shown by an increased intracellular calcium influx. Further studies are now warranted to substantiate and exploit the potential of these novel quinolone-based compounds as orexigenic therapeutics in conditions of cachexia and other metabolic and eating disorders.

Nonpeptide Orexin-2 Receptor Agonist Attenuates Morphine-induced Sedative Effects in Rats.

Sleepiness and decrease in attention are dose-limiting side effects of opioids. The orexin/hypocretin system plays an important role in maintaining wakefulness. This study aimed to explore the potential of a nonpeptide orexin receptor agonist to alleviate morphine-induced sedative effects. Morphine sedative effects were evaluated as changes in electroencephalogram (EEG), locomotor activity, and acoustic startle response in rats (n = 5 to 9 per group). Effects of intracerebroventricular orexin-A and systemic orexin type-2 receptor agonist, YNT-185, on EEG changes induced by morphine were examined. Furthermore, the authors examined effects of morphine administered with or without YNT-185 on locomotor activity and on acoustic startle response. Morphine-induced, frequent, short epochs of increased power (total epoch duration: 0.5 [0.0 to 8.0] s/10 min during baseline vs. 74.0 [49.0 to 115.0] s/10 min during the post-morphine administration period; P = 0.012). EEG analyses revealed that morphine-induced, high-amplitude, slow activity (increase in spectral power of frequencies less than 15 Hz, baseline vs. postmorphine; P < 0.001). Orexin-A and YNT-185 attenuated these changes. Locomotor activity decreased after morphine (268 [103 to 889] ambulatory movement counts during baseline period [20 min] vs. 138 [7 to 434] counts during 40 to 59 min postadministration; P = 0.012), but did not change after morphine with YNT-185 (363 [121 to 636] vs. 864 [381 to 1092] counts, difference within morphine + YNT-185 group; P = 0.071). Startle response latency was longer after morphine (26 [20 to 28] ms) than after morphine with YNT-185 (17 [16 to 18] ms; P = 0.012). Orexin-A and/or YNT-185 attenuated morphine-induced sedative effects assessed by EEG changes and behavioral measures in rats. The authors' results suggest that orexin-2 receptor activation alleviates morphine-induced sedative effects.

Compound 21 (C21), a Selective Angiotensin Type 2 (AT2) Receptor Agonist Attenuates Bleomycin induced Alveolar Epithelial Cell Death

BackgroundIdiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by excessive deposition of collagen‐rich matrix, which progressively leads to respiratory failure and death. Patients with IPF have a reduced survival rate and the disease remains refractory to current therapies. Hence, identifying novel targets and developing effective drugs are of paramount importance. Accumulating evidence indicate that death of alveolar epithelial cells (AEC) is a key event for the initiation of IPF. Bleomycin, a well‐known fibrotic agent is a potent inducer of apoptotic cell death in AEC through synthesis of Angiotensin II (Ang II). While the apoptotic actions of Ang II on AEC are mediated via the angiotensin type 1 (AT1) receptor, the functional role of angiotensin type 2 (AT2) receptor in AEC has not yet been characterized. We hypothesized that stimulation of the angiotensin type 2 (AT2) receptor by a non‐peptide agonist, Compound 21 (C21) protects against bleomycin‐induced alveolar epithelial cell death.MethodsIn this study, we investigated the effects of C21, the selective AT2 receptor agonist against bleomycin‐induced death of human pulmonary alveolar epithelial cells (A549). The MTT (3‐(4, 5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide) assay was performed to determine cell viability of A549.ResultsWe first determined the concentration of bleomycin required for the induction of cell death in cultured A549 cells. A dose‐dependent induction of cell death was obtained with different concentration of bleomycin (μg/mL: % cell death; 1: 30%; 10:42% and 20:61%). Since we observed optimal cell death with 10 μg/mL concentration of bleomycin, we selected this dose for subsequent experiments. Next, we evaluated the cell‐protective effects of C21 at different drug doses (0.001, 0.005, 0.01, 0.05 and 0.1 μM). C21 treatment of bleomycin‐challenged A549 cells (10 μg/mL) produced a dose‐dependent decrease in cell death (μM: % cell death; 0.001:31%; 0.005:29%; 0.01:16%; 0.05:14% and 0.1:9%) as analyzed by the MTT assay. We also observed that treatment of control A549 cells with the above mentioned doses of C21 had little effect on cell proliferation or cell death.ConclusionOur results suggest that C21, the selective AT2 receptor agonist protects against bleomycin‐induced alveolar epithelial cell death. Further studies are warranted to elucidate the mechanisms underlying the cytoprotective effects of C21.Support or Funding InformationAmerican Heart Association Grant (SDG12080302) awarded to Vinayak ShenoyStart‐up Grant from California Health Sciences UniversityThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract WP259: AT2 Receptor-interacting Protein Enhances Protective Effect of AT2 Receptor Stimulation in Ischemic Brain Damage

Objective: Accumulating evidences and previous our research suggest that angiotensin II type 2 (AT 2 ) receptor stimulation could contribute to protection against ischemic brain damage. We have cloned ATIP (AT 2 receptor interacting protein) as a protein interacting specifically with the C-terminal tail of the AT 2 receptor, and reported that ATIP might play key roles in diverse mechanisms of AT 2 receptor signaling. However, the effect of ATIP on ischemic brain damage is still unclear. Therefore, we investigated the effects of the ATIP and compound 21 (C21), a selective non-peptidic AT2 receptor agonist, on focal cerebral ischemia. Method: Ten-week-old male ATIP-transgenic (ATIP-Tg) and littermate (WT) mice were subjected to middle cerebral artery occlusion (MCAO) with silicon-coated micro-filament. C21 (10 μg/kg/day) was administered 2 weeks before MCAO. Twenty-four hours after MCAO, ischemic area was determined. Cerebral blood flow (CBF) before and after MCAO was measured by laser speckle flowmetry. Collateral circulation was evaluated by the perfusion of India ink. Expression of mRNA was determined by real-time RT-PCR. Results: There was no significant difference in ischemic size without C21 treatment between two strains. Treatment with C21 decreased ischemic size in both strains. Interestingly, this protective effect of C21 was more marked in ATIP-Tg compared with WT mice. In CBF of core region of ischemic area, there were no significant differences among all groups. However, the reduction of CBF in penumbra region just after MCA occlusion was attenuated in ATIP-Tg mice with C21 administration. Treatment with C21 tended to increase the cerebral collateral number before MCA occlusion in ATIP-Tg mice. Expression of vascular endothelial growth factor (VEGF) mRNA in the cortex before MCA occlusion did not differ among all groups. Expression of methyl methanesulfonate sensitive 2 (MMS2) as a neuroprotective factor increased in ipsilateral hemisphere of ATIP-Tg mice compared with contralateral hemisphere. Conclusions: These results suggested that ATIP could enhance the cerebral protective effects of AT 2 receptor stimulation at least in part due to the attenuation of CBF reduction and increase of MMS2 expression after ischemia.

Structure of the complement C5a receptor bound to the extra-helical antagonist NDT9513727.

The complement system is a crucial component of the host response to infection and tissue damage. Activation of the complement cascade generates anaphylatoxins including C5a and C3a. C5a exerts a pro-inflammatory effect via the G-protein-coupled receptor C5a anaphylatoxin chemotactic receptor 1 (C5aR1, also known as CD88) that is expressed on cells of myeloid origin. Inhibitors of the complement system have long been of interest as potential drugs for the treatment of diseases such as sepsis, rheumatoid arthritis, Crohn's disease and ischaemia-reperfusion injuries. More recently, a role of C5a in neurodegenerative conditions such as Alzheimer's disease has been identified. Peptide antagonists based on the C5a ligand have progressed to phase 2 trials in psoriasis and rheumatoid arthritis; however, these compounds exhibited problems with off-target activity, production costs, potential immunogenicity and poor oral bioavailability. Several small-molecule competitive antagonists for C5aR1, such as W-54011 and NDT9513727, have been identified by C5a radioligand-binding assays. NDT9513727 is a non-peptide inverse agonist of C5aR1, and is highly selective for the primate and gerbil receptors over those of other species. Here, to study the mechanism of action of C5a antagonists, we determine the structure of a thermostabilized C5aR1 (known as C5aR1 StaR) in complex with NDT9513727. We found that the small molecule bound between transmembrane helices 3, 4 and 5, outside the helical bundle. One key interaction between the small molecule and residue Trp2135.49 seems to determine the species selectivity of the compound. The structure demonstrates that NDT9513727 exerts its inverse-agonist activity through an extra-helical mode of action.

Connective tissue growth factor dependent collagen gene expression induced by MAS agonist AR234960 in human cardiac fibroblasts.

Perspectives on whether the functions of MAS, a G protein-coupled receptor, are beneficial or deleterious in the heart remain controversial. MAS gene knockout reduces coronary vasodilatation leading to ischemic injury. G protein signaling activated by MAS has been implicated in progression of adaptive cardiac hypertrophy to heart failure and fibrosis. In the present study, we observed increased expression of MAS, connective tissue growth factor (CTGF) and collagen genes in failing (HF) human heart samples when compared to non-failing (NF). Expression levels of MAS are correlated with CTGF in HF and NF leading to our hypothesis that MAS controls CTGF production and the ensuing expression of collagen genes. In support of this hypothesis we show that the non-peptide MAS agonist AR234960 increases both mRNA and protein levels of CTGF via ERK1/2 signaling in HEK293-MAS cells and adult human cardiac fibroblasts. MAS-mediated CTGF expression can be specifically blocked by MAS inverse agonist AR244555 and also by MEK1 inhibition. Expression of CTGF gene was essential for MAS-mediated up-regulation of different collagen subtype genes in HEK293-MAS cells and human cardiac fibroblasts. Knockdown of CTGF by RNAi disrupted collagen gene regulation by the MAS-agonist. Our data indicate that CTGF mediates the profibrotic effects of MAS in cardiac fibroblasts. Blocking MAS-CTGF-collagen pathway should be considered for pharmacological intervention for HF.

Hybrid peptide-small molecule oxytocin analogs are potent and selective agonists of the oxytocin receptor

Oxytocin (OT) is a peptide hormone agonist of the oxytocin receptor (OTR) that has been proposed as a therapeutic to treat a number of social and emotional disorders in addition to its current clinical use to induce labor and treat postpartum bleeding. OT is administered intravenously and intranasally rather than orally, in part because its low passive permeability causes low oral bioavailability. Non-peptidic OTR agonists have also been reported, but none with the exquisite potency of the peptide based agonists. In this report, we describe the OTR agonist activity and exposed polarity of a set of truncated OT analogs as well as hybrid peptide-small molecule analogs of OT. Examples of both truncated analogs and peptide-small molecule hybrid analogs are potent and selective OTR agonists. Hybrid agonist 13, which is 232 Da smaller than OT, still retains subnanomolar potency, full agonist activity, and selectivity over V1a. While these compounds were designed to address the low permeability of OT and other full length analogs, we found that reduction in molecular weight and the removal or replacement of the three amino acid tail of OT did not have a significant effect on passive permeability.

Peptidergic control in a fruit crop pest: The spotted-wing drosophila, Drosophila suzukii.

Neuropeptides play an important role in the regulation of feeding in insects and offer potential targets for the development of new chemicals to control insect pests. A pest that has attracted much recent attention is the highly invasive Drosophila suzukii, a polyphagous pest that can cause serious economic damage to soft fruits. Previously we showed by mass spectrometry the presence of the neuropeptide myosuppressin (TDVDHVFLRFamide) in the nerve bundle suggesting that this peptide is involved in regulating the function of the crop, which in adult dipteran insects has important roles in the processing of food, the storage of carbohydrates and the movement of food into the midgut for digestion. In the present study antibodies that recognise the C-terminal RFamide epitope of myosuppressin stain axons in the crop nerve bundle and reveal peptidergic fibres covering the surface of the crop. We also show using an in vitro bioassay that the neuropeptide is a potent inhibitor (EC50 of 2.3 nM) of crop contractions and that this inhibition is mimicked by the non-peptide myosuppressin agonist, benzethonium chloride (Bztc). Myosuppressin also inhibited the peristaltic contractions of the adult midgut, but was a much weaker agonist (EC50 = 5.7 μM). The oral administration of Bztc (5 mM) in a sucrose diet to adult female D. suzukii over 4 hours resulted in less feeding and longer exposure to dietary Bztc led to early mortality. We therefore suggest that myosuppressin and its cognate receptors are potential targets for disrupting feeding behaviour of adult D. suzukii.

Design and synthesis of a novel series of orally active, selective somatostatin receptor 2 agonists for the treatment of type 2 diabetes

The discovery of a novel series of β-methyltryptophan (β MeTrp) derivatives as selective and orally active non-peptide somatostatin receptor 2 (SSTR2) agonists for the treatment of Type 2 diabetes is described. In our previous research, Compound A, β-MeTrp derivative with highly potent and selective SSTR2 agonistic activity IC50 (SSTR2/SSTR5)=0.3/>100 (nM), was identified asa drug candidate for treatment of Type 2 diabetes which lowers significantly plasma glucose level in Wistar fatty rats in its oral administrations. However, as serious increase in AUC and phospholipidosis (PLsis) were observed in its toxicological studies in rats, follow-up compounds were searched to avoid risk of PLsis with reference to their in vitro PLsis potentials evaluated on the basis of accumulation of phospholipids in HepG2 cells exposed to the compounds.It has been found that introduction of a carbonyl group onto the piperidine and piperazine or aniline moiety of compounds A and B reduced markedly the in vitro PLsis potentials. And further modification of the compounds and their evaluation led to a discovery of compounds 3k with lower in vitro PLsis potentials exhibiting lowering effect of hypoglycemia-induced glucagon secretion in SD rats (ED50=1.1mg/kg) and glucose excursion in meal tolerance test in Wistar fatty diabetic rats (MED=3.0mg/kg) in oral administrations.Compound 3k was selected asa new drug candidate of selective and orally active non-peptide SSTR2 agonists for treatment of Type 2 diabetes with low in vivo PLsis potential.

Abstract P237: The At2 Receptor Agonist, C21, Can Also Stimulate Mas and Mrgd Receptors

Background: It is well accepted that Compound 21 (C21) is a highly selective non-peptide angiotensin AT2 receptor agonist. C21 as well as angiotensin (Ang)-(1-7) have cardiovascular protective effects and are opponents of the often detrimental Ang II within the renin-angiotensin system. Since the chemical structure of C21 is similar to the Mas receptor specific non-peptidic agonist AVE0991, and we could recently show that the AT2 receptor blocker, PD123319, can also block the effects of Ang-(1-7) at its natural receptors, Mas and MrgD, we tested whether C21 is also not AT2-specific but can stimulate the two Ang-(1-7) receptors, too. Methods and Results: Using cAMP as readout in receptor-transfected HEK293 cells, we generated pharmacological proof that Mas (EC 50 = 1.995 x 10 -12 M) and MrgD (EC 50 = 2.958 x 10 -9 M) are functional receptors for C21, whereby the three receptor blockers, A779, D-Pro7-Ang-(1-7), and PD123319 showed receptor-specific effects towards C21 signalling. Furthermore, C21 elevated the cAMP concentration in primary cells such as mesangial cells (EC 50 = 1.12 x 10 -6 M). However, significant increase in cAMP levels, but not in PKA activity, was still detectable in mesangial cells isolated from AT2-deficient mice, but completely blunted in Mas/MrgD-double knockouts. Finally, in silico modelling was performed to illustrate the structural similarities and differences between C21, AVE0991, and Ang-(1-7). Conclusions: Our results identify C21 as not being a specific AT2 receptor agonist but also interacting with the two Ang-(1-7) receptors, Mas and MrgD. Therefore, the partial overlap in beneficial effects of Ang-(1-7) and C21 might be based on the stimulation of the same receptors under specific pathophysiological circumstances. This also enforces the revisit of such publications which concluded on AT2 function by only using C21.

Abstract P450: AT2 Receptor Stimulation Reduces Ischemic Brain Damage Through AT2 Receptor-interacting Protein Signal

Objectives: We reported the preventive effects of angiotensin II type 2 (AT2) receptor stimulation on ischemic brain damage. Moreover, we have cloned ATIP (AT2 receptor interacting protein) as a protein interacting specifically with the C-terminal tail of the AT2 receptor, and suggest that ATIP should play key roles in diverse mechanisms of AT2 receptor actions. However, the effect of ATIP on ischemic brain damage is unclear. Therefore, we investigated the effects of the ATIP and compound 21 (C21), a selective non-peptide AT2 receptor agonist, on focal cerebral ischemia. Method: Ten-week-old male ATIP-transgenic (ATIP-Tg) and littermate (WT) mice were subjected to middle cerebral artery occlusion (MCAO) with silicon-coated micro-filament. C21 (10 μg/kg/day) was administered 2 weeks before MCAO. Twenty-four hours after MCAO, ischemic volume was determined and depicted as mm 3 . Expression of methyl methanesulfonate sensitive 2 (MMS2) mRNA as a neuroprotective factor was determined by real-time RT-PCR. Cerebral blood flow (CBF) before and after MCA occlusion were measured by laser speckle flowmetry. Collateral circulation was evaluated by the perfusion of India ink. Results: Systolic blood pressure did not differ among all groups. There was no significant difference in ischemic size without C21 treatment between two strains (WT, 80 mm 3 ; ATIP-Tg, 75 mm 3 ). Treatment with C21 significantly decreased ischemic size in both strains (WT, 66 mm 3 ; ATIP-Tg, 50 mm 3 ). Interestingly, this protective effect of C21 was more marked in ATIP-Tg compared with WT mice (WT, 16% (66 of 80); ATIP-Tg, 27% (50 of 75) reduction, respectively). MMS2 expression increased in ipsilateral hemisphere of ATIP-Tg mice compared with contralateral hemisphere. There were no significant differences in CBF of core region of ischemic area, among all groups. However, the reduction of CBF in penumbra region after MCA occlusion was attenuated in ATIP-Tg mice with C21 administration. Treatment with C21 tended to increase the cerebral collateral number before MCA occlusion in ATIP-Tg mice not in WT. Conclusions: These results suggested that ATIP could enhance the cerebral protective effects of AT 2 receptor stimulation at least in part due to the increase of CBF and MMS2 expression after ischemia.

Abstract P206: Anti-hyperglycemic Effects of Angiotensin-II Type 2 Receptor Activation by C21 in High Sodium Diet Fed Obese Zucker Rats

Intake of high sodium diet (HSD) has been implicated in development of insulin resistance and obese subjects are salt-sensitive. Recently, we reported that stimulation of angiotensin-II type 2 receptor (AT 2 R) by selective non-peptide agonist C21 prevents salt-sensitive hypertension and oxidative stress, however effect of AT 2 R activation on insulin resistance and circulating lipids in obese animals fed HSD is unknown. Therefore, we investigated effects of AT 2 R activation by C21 (1 mg/kg/day, s.c. by Alzet osmotic pump) on insulin resistance and circulating lipids in obese Zucker rats (OZR) fed HSD (4%) for 14 days. High-salt diet feeding significantly increased fasting plasma glucose (p&lt;0.05) and insulin (p&lt;0.05), and caused glucose intolerance as evident by oral glucose tolerance test (p&lt;0.05). Concurrent treatment with C21 reduced plasma glucose (p&lt;0.05) and insulin (p&lt;0.05) and improved glucose tolerance (p&lt;0.05). Circulating plasma free fatty acids (FFA) and triglycerides were unchanged in OZRs fed normal diet or HSD. Interestingly, however, C21 treatment lowered plasma FFA (p&lt;0.05), but not triglycerides. Results suggest that AT 2 R activation may prevent onset of hyperglycemia in obese animals fed HSD by improving insulin sensitivity, however, target organ involved in AT 2 R-mediated effects remains to be explored.

Anti-fibrotic Potential of AT2 Receptor Agonists

There are a number of therapeutic targets to treat organ fibrosis that are under investigation in preclinical models. There is increasing evidence that stimulation of the angiotensin II type 2 receptor (AT2R) is a novel anti-fibrotic strategy and we have reviewed the published in vivo preclinical data relating to the effects of compound 21 (C21), which is the only nonpeptide AT2R agonist that is currently available for use in chronic preclinical studies. In particular, the differential influence of AT2R on extracellular matrix status in various preclinical fibrotic models is discussed. Collectively, these studies demonstrate that pharmacological AT2R stimulation using C21 decreases organ fibrosis, which has been most studied in the setting of cardiovascular and renal disease. In addition, AT2R-mediated anti-inflammatory effects may contribute to the beneficial AT2R-mediated anti-fibrotic effects seen in preclinical models.

In vitro pharmacological characterization of a novel unbiased NOP receptor-selective nonpeptide agonist AT-403.

Nociceptin/orphanin FQ (N/OFQ) regulates several biological functions via selective activation of the N/OFQ receptor (NOP), a member of the opioid receptor family. We recently identified a new high affinity and highly selective NOP agonist AT‐403. In this study, we characterized the functional profile of AT‐403 and compared it to other known nonpeptide NOP agonists Ro 65‐6570, Ro 2q, SCH‐221510, MCOPPB, AT‐202 and SCH‐486757, using the following assays: GTP γ[35S] stimulated binding, calcium mobilization assay in cells‐expressing human NOP or classical opioid receptors and chimeric G proteins, bioluminescence resonance energy transfer (BRET) based assay for studying NOP receptor interaction with G protein and arrestin, and the electrically stimulated mouse vas deferens bioassay. All compounds behaved as NOP full agonists consistently showing the following rank order of potency MCOPPB > AT‐403 > Ro 65‐6570 = Ro 2q > SCH‐221510 > AT‐202 > SCH‐486757. AT‐403 and MCOPPB displayed the highest NOP selectivity both at human and murine receptors. Interestingly, while all the other nonpeptide NOP agonists displayed bias toward G protein‐mediated signaling in the BRET assay, AT‐403, similar to the natural ligand N/OFQ, behaved as an unbiased agonist, activating G‐protein‐mediated function as well as arrestin recruitment. AT‐403 may be a useful nonpeptide tool compound to study the pharmacology of NOP activation in disease states.

Nonpeptide orexin type-2 receptor agonist ameliorates narcolepsy-cataplexy symptoms in mouse models

Narcolepsy-cataplexy is a debilitating disorder of sleep/wakefulness caused by a loss of orexin-producing neurons in the lateroposterior hypothalamus. Genetic or pharmacologic orexin replacement ameliorates symptoms in mouse models of narcolepsy-cataplexy. We have recently discovered a potent, nonpeptide OX2R-selective agonist, YNT-185. This study validates the pharmacological activity of this compound in OX2R-transfected cells and in OX2R-expressing neurons in brain slice preparations. Intraperitoneal, and intracerebroventricular, administration of YNT-185 suppressed cataplexy-like episodes in orexin knockout and orexin neuron-ablated mice, but not in orexin receptor-deficient mice. Peripherally administered YNT-185 also promotes wakefulness without affecting body temperature in wild-type mice. Further, there was no immediate rebound sleep after YNT-185 administration in active phase in wild-type and orexin-deficient mice. No desensitization was observed after repeated administration of YNT-185 with respect to the suppression of cataplexy-like episodes. These results provide a proof-of-concept for a mechanistic therapy of narcolepsy-cataplexy by OX2R agonists.

Investigation of pyrazolo-sulfonamides as putative small molecule oxytocin receptor agonists

The neuropeptide oxytocin has been implicated in multiple central nervous system functions in mammalian species. Increased levels have been reported to improve trust, alleviate symptoms related to autism and social phobias, and reduce social anxiety. Hoffman-La Roche published a patent claiming to have found potent small molecule oxytocin receptor agonists, smaller than the first non-peptide oxytocin agonist reported, WAY 267,464. We selected two of the more potent compounds from the patent and, in addition, created WAY 267,464 hybrid structures and determined their oxytocin and vasopressin receptor activity. Human embryonic kidney and Chinese hamster ovary cells were used for the expression of oxytocin or vasopressin 1a receptors and activity assessed via IP1 accumulation assays and calcium FLIPR assays. The results concluded that the reported compounds in the patent and the hybrid structures have no activity at the oxytocin or vasopressin 1a receptors.

Vasopressin and Related Peptides; Potential Value in Diagnosis, Prognosis and Treatment of Clinical Disorders

Vasopressin (AVP) and its receptors play a pivotal role in maintaining body homeostasis under physiological and pathophysiological conditions. As a consequence, the vasopressin system has emerged as an important target for both diagnostic and therapeutic applications in a number of medical conditions. Stoichiometric generation of AVP with copeptin, which is relatively accessible in the blood for measurements, makes copeptin a valuable surrogate of AVP. In this review, we present the regulation of release of AVP and activation of V1a, V1b, and V2 vasopressin receptors under physiological and pathological conditions. We make a survey of the role of AVP in: the regulation of the cardiovascular system; body fluid osmolality; natraemia; endocrine regulation; food intake; metabolism; circadian rhythmicity, immunological processes; and in the formation of learning, memory, cognition, and emotional and social behaviours. We also discuss the significance of the inappropriate functioning of the vasopressin system for: the development of cardiovascular diseases; disturbances of the water-electrolyte balance; energy metabolism; inflammatory processes; pain; neurogenic stress; memory disorders; depression; anxiety; autism; and schizophrenia. The structure and biological properties of peptide and non-peptide agonists and antagonists of V1a, V1b and V2 vasopressin receptors are presented and the potential use of copeptin and the current and likely indications for AVP agonists and antagonists in the diagnosis and therapeutics of multiple pathological conditions is discussed.