ABSTRACT
Kappa opioid receptors and their endogenous neuropeptide ligand, dynorphin A, are densely localized in limbic and cortical areas comprising the brain reward system, and appear to play a key role in modulating stress and mood. Growing literature indicates that kappa receptor antagonists may be beneficial in the treatment of mood and addictive disorders. However, existing literature on kappa receptor antagonists has used extensively JDTic and nor-BNI which exhibit long-lasting pharmacokinetic properties that complicate experimental design and interpretation of results. Herein, we report for the first time the in vitro and in vivo pharmacological profile of a novel, potent kappa opioid receptor antagonist with excellent selectivity over other receptors and markedly improved drug-like properties over existing research tools. LY2456302 exhibits canonical pharmacokinetic properties that are favorable for clinical development, with rapid absorption (t(max): 1-2 h) and good oral bioavailability (F = 25%). Oral LY2456302 administration selectively and potently occupied central kappa opioid receptors in vivo (ED50 = 0.33 mg/kg), without evidence of mu or delta receptor occupancy at doses up to 30 mg/kg. LY2456302 potently blocked kappa-agonist-mediated analgesia and disruption of prepulse inhibition, without affecting mu-agonist-mediated effects at doses >30-fold higher. Importantly, LY2456302 did not block kappa-agonist-induced analgesia one week after administration, indicating lack of long-lasting pharmacodynamic effects. In contrast to the nonselective opioid antagonist naltrexone, LY2456302 produced antidepressant-like effects in the mouse forced swim test and enhanced the effects of imipramine and citalopram. LY2456302 reduced ethanol self-administration in alcohol-preferring (P) rats and, unlike naltrexone, did not exhibit significant tolerance upon 4 days of repeated dosing. LY2456302 is a centrally-penetrant, potent, kappa-selective antagonist with pharmacokinetic properties favorable for clinical development and activity in animal models predictive of efficacy in mood and addictive disorders.
Subject(s)
Benzamides/pharmacology , Depression/drug therapy , Narcotic Antagonists/pharmacology , Pyrrolidines/pharmacology , Receptors, Opioid, kappa/antagonists & inhibitors , Reflex, Startle/drug effects , Sensory Gating/drug effects , Analgesia , Animals , Antidepressive Agents/pharmacokinetics , Antidepressive Agents/pharmacology , Antidepressive Agents/therapeutic use , Benzamides/pharmacokinetics , Benzamides/therapeutic use , Disease Models, Animal , Ethanol/administration & dosage , Male , Mice , Narcotic Antagonists/pharmacokinetics , Narcotic Antagonists/therapeutic use , Pyrrolidines/pharmacokinetics , Pyrrolidines/therapeutic use , Rats , Self AdministrationABSTRACT
BACKGROUND: Selective kappa opioid receptor antagonism is a promising experimental strategy for the treatment of depression. The kappa opioid receptor antagonist, LY2456302, exhibits ~30-fold higher affinity for kappa opioid receptors over mu opioid receptors, which is the next closest identified pharmacology. METHODS: Here, we determined kappa opioid receptor pharmacological selectivity of LY2456302 by assessing mu opioid receptor antagonism using translational pupillometry in rats and humans. RESULTS: In rats, morphine-induced mydriasis was completely blocked by the nonselective opioid receptor antagonist naloxone (3mg/kg, which produced 90% mu opioid receptor occupancy), while 100 and 300 mg/kg LY2456302 (which produced 56% and 87% mu opioid receptor occupancy, respectively) only partially blocked morphine-induced mydriasis. In humans, fentanyl-induced miosis was completely blocked by 50mg naltrexone, and LY2456302 dose-dependently blocked miosis at 25 and 60 mg (minimal-to-no blockade at 4-10mg). CONCLUSIONS: We demonstrate, for the first time, the use of translational pupillometry in the context of receptor occupancy to identify a clinical dose of LY2456302 achieving maximal kappa opioid receptor occupancy without evidence of significant mu receptor antagonism.
Subject(s)
Benzamides/pharmacology , Narcotic Antagonists/pharmacology , Pupil/drug effects , Pyrrolidines/pharmacology , Receptors, Opioid, kappa/antagonists & inhibitors , Adolescent , Adult , Animals , Benzamides/blood , Cross-Over Studies , Dose-Response Relationship, Drug , Double-Blind Method , Fentanyl/pharmacology , Humans , Male , Middle Aged , Miosis/chemically induced , Miosis/drug therapy , Morphine/pharmacology , Mydriasis/chemically induced , Mydriasis/drug therapy , Naltrexone/pharmacology , Narcotic Antagonists/blood , Narcotics/pharmacology , Pupil/physiology , Pyrrolidines/blood , Rats, Sprague-Dawley , Receptors, Opioid, kappa/agonists , Receptors, Opioid, kappa/metabolism , Young AdultABSTRACT
General opioid receptor antagonists reduce food intake and body weight in rodents, but the contributions of specific receptor subtypes are unknown. We examined whether genetic deletion of the kappa-opioid receptor (KOR) in mice alters metabolic physiology. KOR-knockout (KO) and wild-type (WT) mice were fed a high-energy diet (HED) for 16 wk. KO mice had 28% lower body weight and 45% lower fat mass when compared to WT mice fed an HED. No differences in caloric intake were found. An HED reduced energy expenditure in WT mice, but not in KO mice. KOR deficiency led to an attenuation of triglyceride synthesis in the liver. Malonyl CoA levels were also reduced in response to an HED, thereby promoting hepatic beta-oxidation. Glycemic control was also found to be improved in KO mice. These data suggest a key role for KORs in the central nervous system regulation of the metabolic adaptation to an HED, as we were unable to detect expression of KOR in liver, white adipose tissue, or skeletal muscle in WT mice. This study provides the first evidence that KORs play an essential physiological role in the control of hepatic lipid metabolism, and KOR activation is a permissive signal toward fat storage.-Czyzyk, T. A., Nogueiras, R., Lockwood, J. F., McKinzie, J. H., Coskun, T., Pintar, J. E., Hammond, C., Tschöp, M. H., Statnick, M. A. kappa-Opioid receptors control the metabolic response to a high-energy diet in mice.
Subject(s)
Energy Intake , Liver/metabolism , Receptors, Opioid, kappa/metabolism , Triglycerides/biosynthesis , Adipose Tissue, White/metabolism , Animals , Body Weight/genetics , Gene Expression Regulation/genetics , Mice , Mice, Knockout , Muscle, Skeletal/metabolism , Organ Specificity/genetics , Oxidation-Reduction , Receptors, Opioid, kappa/geneticsABSTRACT
A series of 6-bicycloaryloxynicotinamides were identified as opioid receptor antagonists at mu, kappa, and delta receptors. Compounds in the 6-(2,3,4,5-tetrahydro-1H-benzo[c]azepin-7-yloxy)nicotinamide scaffold exhibited potent in vitro functional antagonism at all three receptors.
Subject(s)
Amides/chemistry , Carboxylic Acids/chemistry , Ethers/chemistry , Ethers/pharmacology , Narcotic Antagonists , Acrylic Resins/chemistry , Ethers/chemical synthesis , Molecular Structure , Receptors, Opioid/metabolism , Structure-Activity RelationshipABSTRACT
LY255582 is a pan opioid selective receptor antagonist that has been shown to have high affinity for mu, delta, and kappa receptors in vitro. In order to better understand the in vivo opioid receptor selectivity of LY255582, we developed in vivo receptor occupancy assays in the rat for the opioid mu, kappa and delta receptors using the occupancy tracers naltrexone, GR103545 and naltriben respectively. Individual assays for each target were established and then a "triple tracer" assay was created where all three tracers were injected simultaneously, taking advantage of LC/MS/MS technology to selectively monitor brain tracer levels. This is the first report of a technique to concurrently measure receptor specific occupancy at three opioid receptors in the same animal. The opioid subtype selective antagonists cyprodime, JDTic and naltrindole were used to validate selectivity of the assay. Examination of LY255582 in dose-occupancy experiments demonstrated a relative order of potency of mu>kappa>delta, reproducing the previously reported order determined with in vitro binding.
Subject(s)
Brain/metabolism , Cyclohexanes/pharmacology , Narcotic Antagonists/pharmacology , Piperidines/pharmacology , Receptors, Opioid, delta/metabolism , Receptors, Opioid, kappa/metabolism , Receptors, Opioid, mu/metabolism , Animals , Binding, Competitive , Brain/drug effects , Chromatography, Liquid/methods , Cyclohexanes/administration & dosage , Injections, Intravenous , Male , Mice , Mice, Knockout , Narcotic Antagonists/administration & dosage , Obesity/drug therapy , Obesity/metabolism , Piperidines/administration & dosage , Protein Binding , Rats , Receptors, Opioid, delta/antagonists & inhibitors , Receptors, Opioid, kappa/antagonists & inhibitors , Receptors, Opioid, mu/antagonists & inhibitors , Receptors, Opioid, mu/genetics , Tandem Mass Spectrometry/methodsABSTRACT
A structurally unique and new class of opioid receptor antagonists (OpRAs) that bear no structural resemblance with morphine or endogenous opioid peptides has been discovered. A series of carboxamido-biaryl ethers were identified as potent receptor antagonists against mu, kappa and delta opioid receptors. The structure-activity relationship indicated para-substituted aryloxyaryl primary carboxamide bearing an amine tether on the distal phenyl ring was optimal for potent in vitro functional antagonism against three opioid receptor subtypes.
Subject(s)
Ethers/chemical synthesis , Ethers/pharmacology , Narcotic Antagonists , Animals , CHO Cells , Cricetinae , Cricetulus , Drug Design , Guanosine 5'-O-(3-Thiotriphosphate)/antagonists & inhibitors , Humans , Molecular Conformation , Receptors, Opioid, delta/antagonists & inhibitors , Receptors, Opioid, kappa/antagonists & inhibitors , Receptors, Opioid, mu/antagonists & inhibitors , Structure-Activity RelationshipABSTRACT
Differences in the anorectic activity of morphinan (e.g., naltrexone) and 3,4-dimethyl-4-(3-hydroxyphenyl)piperidine (4PP) opioid receptor antagonists have been described. In an attempt to explain these differences, the influence of Na(+) on opioid binding affinity and functional activity of 4PP antagonists was compared to other opioid antagonists. The binding affinities of neutral antagonists were unaffected by the addition of Na(+), whereas that for the peptide, inverse agonist N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH (ICI174864) was increased. Similarly, the binding affinities of the 4PP antagonist (3R,4R)-1-((S)-3-hydroxy-3-cyclohexylpropyl)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidine (LY255582) and other 4PP antagonists were increased in the presence of Na(+) with the greatest effects at the delta opioid receptor followed by the mu and kappa opioid receptors, respectively. Similar to ICI174864, 4PP antagonists were found to inhibit basal GTPgamma[(35)S] binding at the delta opioid receptor indicating inverse agonist activity. A correlation was observed between the binding affinities in the presence of Na(+), the inverse agonist potency, and the anorectic potency of 4PP antagonists. These data suggest that 4PP antagonists differ from morphinan antagonists in their inverse agonist activity and suggest a relationship between inverse agonism and anorectic activity.