RESUMO
This paper describes the chemical synthesis and CCK-B and CCK-A receptor binding affinities of a series of compounds in which the central amide bond of the CCK-B "dipeptoid" ligand tricyclo[3.3.1.1(3,7)]dec-2-yl [R-(R*,S*)]-[2-[[1-(hydroxymethyl)- 2-phenylethyl]amino]-1-(1H-indol-3-ylmethyl)-2-oxoethyl]carb amate (4) (CCK-B IC50 = 852 nM), and tricyclo[3.3.1.1(3,7)]dec-2-yl (R)-[1-(1H-indol-3-ylmethyl)-1-methyl- 2-oxo-2-[(2-phenylethyl)amino]ethyl]carbamate (23) (CCK-B IC50 = 32 nM) is replaced by 11 different amide replacements. These replacements are the methyleneamino (CH2NH), the reverse amide (NHCO), the ester (COO), the N-methylamide (CONMe), the thioamide (CSNH), the N-acetylmethyleneamino (CH2NAc), the cis double bond (CHCH), the ethylene (CH2CH2), the thiolester (COS), the hydroxyethylene (CHOHCH2), and a 4,5-dihydro-1,3-thiazole. Most of the replacements have weaker affinity and reduced selectivity for the CCK-B receptor than the parent amide. However, this affinity can be improved by appending a fumarate side chain to the phenethyl group, e.g. tricyclo[3.3.1.1(3,7)]dec-2-yl-3-(1H-indol-3-yl-methyl)-3-methyl-4 ,9- dioxo-7-phenyl-5,13-dioxa-2,8-diazatetradec-10-enoate (36) (CCK-B IC50 = 38.8 nM). Replacement of the amide of compound 4 with a 4,5-dihydro-1,3-thiazole gives tricyclo[3.3.1.1(3,7)]dec-2-yl [1-[4,5-dihydro-4-(phenylmethyl)-2- thiazolyl]-2-(1H-indol-3-yl)ethyl]carbamate (5), which is selective for the CCK-A receptor (CCK-A IC50 = 125 nM, CCK-B IC50 = 2580 nM, ratio = 21). The methyleneamino and hydroxyethylene replacements, which have been used elsewhere as transition-state inhibitors of enzymes, are poor mimics of the amide in these CCK-B receptor ligands. Some of the steric, lipophilic, and hydrogen bonding properties of amide replacements incorporated into the simple amide, N-methylacetamide, have been quantified with the aid of molecular modeling. These data will contribute to the rational selection of amide bond replacements in other substrates.
Assuntos
Amidas/síntese química , Colecistocinina/análogos & derivados , Amidas/farmacologia , Indóis/farmacologia , Meglumina/análogos & derivados , Meglumina/farmacologia , Modelos Moleculares , Receptores da Colecistocinina/efeitos dos fármacos , Receptores da Colecistocinina/metabolismo , Relação Estrutura-AtividadeRESUMO
We have investigated the pharmacological properties of MEN 11467, a novel partially retro-inverse peptidomimetic antagonist of tachykinin NK(1) receptors. MEN 11467 potently inhibits the binding of [(3)H] substance P (SP) to tachykinin NK(1) receptors in the IM9 limphoblastoid cell line (pK(i) = 9.4 +/- 0.1). MEN 11467 is highly specific for the human tachykinin NK(1) receptors, since it has negligible effects (pK(i) <6) on the binding of specific ligands to tachykinin NK(2) or NK(3) receptors and to a panel of 30 receptors ion channels unrelated to tachykinin receptors. The antagonism exerted by MEN 11467 at tachykinin NK(1) receptors is insurmountable in saturation binding experiments, both K(D) and B(max) of SP were significantly reduced by MEN 11467 (0.3-10 nM). In the guinea-pig isolated ileum, MEN 11467 (0.03-1 nM) produced a nonparallel rightward shift of the concentration-response curve to SP methylester with a concomitant reduction of the Emax to the agonist (pK(B) = 10.7 +/- 0.1). Moreover the antagonist activity of MEN 11467 was hardly reversible despite prolonged washout. In vivo, MEN 11467 produced a long lasting (> 2-3h) dose-dependent antagonism of bronchoconstriction induced by the selective tachykinin NK(1) receptor agonist, [Sar(9), Met(O(2))(11)]SP in anaesthetized guinea-pigs (ID(50)s' = 29+/-5, 31+/-12 and 670+/-270 microg/kg, after intravenous, intranasal and intraduodenal administration, respectively), without affecting bronchoconstriction induced by methacholine. After oral administration MEN 11467 produced a dose-dependent inhibition of plasma protein extravasation induced in guinea-pig bronchi by [Sar(9), Met(O(2))(11)] (ID(50) = 6.7 +/- 2 mg/kg) or by antigen challenge in sensitized animals (ID(50) = 1.3 mg/kg). After i.v. administration MEN 11467 weakly inhibited the GR 73632-induced foot tapping behaviour in gerbil (ED(50) = 2.96 +/- 2 mg/kg), indicating a poor ability to block central tachykinin NK(1) receptors. These results demonstrate that MEN 11467 is a potent, highly selective and orally effective insurmountable pseudopeptide antagonist of peripheral tachykinin NK(1) receptors with a long duration of action.
Assuntos
Cicloexilaminas/farmacologia , Indóis/farmacologia , Antagonistas dos Receptores de Neurocinina-1 , Substância P/análogos & derivados , Administração Oral , Animais , Broncoconstrição/efeitos dos fármacos , Cicloexilaminas/administração & dosagem , Cicloexilaminas/química , Gerbillinae , Cobaias , Indóis/administração & dosagem , Indóis/química , Linfoma/metabolismo , Masculino , Fragmentos de Peptídeos/farmacologia , Receptores da Neurocinina-2/antagonistas & inibidores , Receptores da Neurocinina-3/antagonistas & inibidores , Substância P/metabolismo , Substância P/farmacologia , Células Tumorais CultivadasRESUMO
In this study we investigated the pharmacological properties of MEN 11149, 2-(2-naphthyl)-1-N-[(1R,2S)-2-N-[1(H)indol-3-ylcarbonyl]aminocy clohexanecarbonyl]-1-[N'-methyl-N'-(4-methylphenylacetyl)]di aminoethane, a novel partially retro-inverse pseudo peptide antagonist of tachykinin NK1 receptors. MEN 11149 potently inhibits the binding of [3H]substance P to tachykinin NK1 sites in IM9 cells (pKi = 8.5 +/- 0.1). The compound is highly specific for the human tachykinin NK1 receptors, since it has negligible effects (pKi < 6) on the binding of specific ligands to tachykinin NK2, NK3 receptors and a battery of central and peripheral receptors or ion channels. The tachykinin NK1 receptor antagonism of MEN 11149 appears to be insurmountable since, in saturation binding experiments, both K(D) and Bmax are significantly affected by incubation with the compound (1-30 nM). In isolated guinea-pig ileum, MEN 11149 (0.1-100 nM) shifts to the right in a non-parallel way the substance P methyl ester-induced cumulative concentration-response curve with progressive inhibition of the maximal response (pK(B) = 9.6 +/- 0.1). When tested for reversibility at 5 nM in the same preparation, the compound displays a slow dissociation rate compared to the fast dissociation rate with FK888 (N2-[(4R)-4-hydroxy-1-(1-methyl-1H-indol-3-yl)carbonyl-L-prolyl]-N-methy l-N-phenylmethyl-L-3-(2-naphthyl)alaninamide) at 5 nM. In the same preparation, MEN 11149 (10 microM) did not affect the cumulative concentration-response curve to acetylcholine. In vivo, MEN 11149 dose dependently antagonizes [Sar9,Met(O2)11]substance P-induced bronchoconstriction in anaesthetized guinea-pigs (ID50 = 83 +/- 31 nmol/kg i.v.). The duration of the effect exceeds 3 h. MEN 11149 does not affect the bronchoconstriction induced by neurokinin A. The compound dose dependently inhibits [Sar9,Met(O2)11]substance P-induced plasma protein extravasation in guinea-pig bronchi whether administered intravenously (ID50 = 0.22 +/- 0.02 micromol/kg) or orally (ID50 = 0.97 +/- 0.21 micromol/kg). These results demonstrate that MEN 11149 is a potent, highly selective and orally effective insurmountable antagonist of tachykinin NK1 receptors with a long duration of action.
Assuntos
Íleo/efeitos dos fármacos , Indóis/farmacologia , Contração Muscular/efeitos dos fármacos , Naftalenos/farmacologia , Receptores de Taquicininas/antagonistas & inibidores , Taquicininas/metabolismo , Administração Oral , Animais , Proteínas Sanguíneas/efeitos dos fármacos , Broncoconstrição/efeitos dos fármacos , Cobaias , Humanos , Íleo/fisiologia , Canais Iônicos/efeitos dos fármacos , Masculino , Receptores de Taquicininas/efeitos dos fármacos , Substância P/metabolismo , Substância P/farmacologia , Células Tumorais Cultivadas/efeitos dos fármacosRESUMO
We have designed and synthesized a conformationally homogeneous series of cyclic pentapeptides of the general structure c[Pro-aa(i)-D-Tic-Oic-aa(i + 3)] which adopt a type-II' beta-turn conformation believed important for high affinity antagonism of the bradykinin (BK) B2 receptor. We incorporated D-Tic and octahydroindole-2-carboxylic acid (Oic) residues (present in known active antagonists) in a cyclic pentapeptide that would place the D-aa in the i + 1 position of the beta-turn and a proline as a bridge between the C- and N-termini sides of the turn. In positions i and i + 3 alkyl, aromatic, polar or charged amino acids could be introduced without dramatically changing the overall structure. Ten analogues were studied using 1H nuclear magnetic resonance (NMR) and evaluated for their binding affinity for the human B2 receptor. The NMR data in dimethylsulfoxide (DMSO) confirmed the structural homogeneity within the class and, on the basis of this, one representative member of the series was chosen for a detailed structure determination using NMR data in sodium dodecylsulphate (SDS) micelles and molecular dynamics calculations. Despite the structural similarity, the binding affinity of the ten analogues was strongly influenced by the nature of the side-chains in positions i and i + 3, with the doubly charged analogue 49 (pKi = 6.2) proving best. This compound may serve as the starting point for the discovery of new non-peptide bradykinin B2 receptor antagonists.
Assuntos
Antagonistas dos Receptores da Bradicinina , Peptídeos Cíclicos/síntese química , Peptídeos/síntese química , Receptores da Bradicinina/química , Dimetil Sulfóxido/química , Humanos , Cinética , Espectroscopia de Ressonância Magnética , Micelas , Modelos Químicos , Peptídeos/química , Peptídeos Cíclicos/química , Ligação Proteica , Conformação Proteica , Receptor B2 da Bradicinina , Dodecilsulfato de Sódio/química , Tensoativos/farmacologiaRESUMO
In the course of a program aimed at synthesizing novel, potent NK-1 tachykinin receptor antagonists, we developed upon a bioactive model by comparing the low energy structures of a series of peptide and nonpeptide Substance P antagonists. The comparison was based on the superimposition of the aromatic rings, assuming that the rest of the molecule behaves predominantly as a template to arrange the key aromatic groups in the right spatial position. A series of 2-aminocyclohexane carboxylic acid analogues were then selected as the best templates for reproducing the postulated bioactive structure, leading to several pseudo-peptides with interesting biological activity. According to the molecular modeling, these compounds exhibit a neat parallel facing of the indolyl and naphthyl groups at about 3 A distance. Ultraviolet absorption and steady state fluorescence measurements support this conclusion, showing a linear correlation between the spectral properties and the binding affinity of these analogues. Stacking of the indole ring with naphthalene gives rise to a complex characterized by a well-defined molar extinction coefficient. Consistently, steady state and lifetime fluorescence measurements suggest that the quenching process is ascribable to ground-state interactions between the chromophores. Implications of the pi stacking propensity of aromatic groups in the biological activity of the compounds examined are briefly discussed.