New isoxazole derivatives with a potent and selective beta 2-adrenergic activity

A series of 1-(3-subst-5-isoxazolyl)-2-alkylaminoethanol derivatives was synthesized and tested in order to evaluate the effectiveness of the isoxazole ring in replacing the catechol moiety of beta-adrenergic compounds. Direct binding studies and the influence on beta-receptors mediated responses in isolated guinea-pig atria and guinea-pig trachea were investigated to determine the pharmacological profile of the new derivatives. The results indicate that some derivatives with proper substitution in the isoxazole ring and in the aminoalcohol chain displayed a marked selectivity towards beta 2 tracheal receptors. In vivo studies confirmed this profile, and the derivative 1-(3-bromo-5-isoxazolyl)-2-tert.butyl aminoethanol hydrochloride was selected and further developed as a potential bronchodilatory agent.     

Structure-activity relationship studies of phenoxypropanolamine derivatives for beta 3-adrenergic activity

In this study, some compounds of phenoxypropanolamine (SWR-0342SA) derivatives were found to possess beta 3-adrenoceptor (beta 3-AR) agonistic activity. Addition and deletion of the substituents on phenoxyacetate, chain length variation between two aromatic rings, conversion of phenoxypropanolamine to phenylethanolamine, insertion of double bonds and another ether group in the side chain between two phenyl rings in SWR-0342SA derivatives resulted in novel phenoxypropanolamine and phenylethanolamine compounds. This study was performed to evaluate the structural modification of the parent SWR-0342SA and their effects on the binding affinities as well as functional activities of these derivatives using COS-7 cells and CHO cells expressing human beta 1, beta 2, beta 3-AR and only beta 3-AR respectively. Compounds SWR-0342SA, SWR-0339SA (S-enantiomer with trans-ethylidene group), SWR-0315NA (non-isomeric with racemic ethylidene group and sodium salt), and SWR-0334NA (non-isomeric with trans-ethylidene group and sodium salt), all belonging to phenoxypropanolamine group, were found to have high binding and functional activities and were supposed to be potent beta 3-AR agonists. Since many of the phenoxypropanolamine compounds acts as antagonists to beta 1- and beta 2-ARs, these derivatives have also been evaluated for their affinity to beta 1- and beta 2-ARs. The pKi values of these derivatives to beta-AR subtypes were also compared. These compounds show little selectivities towards beta 3-AR subtypes.     

New beta 2-adrenergic agonist aerosols

The beta 2-adrenergic agonists are reviewed in terms of their dose-response characteristics, and two newer agents, fenoterol hydrobromide and bitolterol mesylate aerosols, are reviewed in relation to older agents. The fenoterol aerosol contains a more potent beta 2-adrenergic agonist dose per puff than the other aerosols but, when given in equipotent doses, offers no advantage over available agents. Bitolterol mesylate is a prodrug that is hydrolyzed to the active beta 2-adrenergic agonist colterol by lung esterases. Bitolterol demonstrates an improved bronchoselectivity in animals, but there are insufficient comparative data in humans. Tachycardia is the dose-limiting toxicity for all beta 2-adrenergic agonists. Currently available data do not suggest an important improvement in duration of action for the newer agents over terbutaline or albuterol. Aerosol administration improves bronchoselectivity of all the agents. Optimal use of beta 2-adrenergic agonist aerosols requires understanding of the variable dose-response characteristics. The type of delivery system and patient technique are important variables in determining the dose delivered. Tube-spacer devices attached to aerosol canisters can significantly improve delivery of the beta 2-adrenergic agonists to the lungs in patients unable to synchronize actuation and inspiration. They provide minimal to no improvement in patients who can perform the appropriate technique. Aerosol administration is the route of choice for beta 2-adrenergic agonists for prophylaxis of exercise-induced bronchospasm; albuterol and terbutaline provide a prolonged duration of action with excellent beta 2-adrenergic selectivity. Patients should be carefully instructed in the optimal use of metered-dose inhalers, and some patients may benefit from use of tube-spacers.     

Predictive QSAR modeling study on berberine derivatives with hypolipidemic activity

Berberine (BBR), isolated from a Chinese herb, is identified as a new cholesterol‐lowering small molecule, and hundreds of berberine derivatives have been obtained for optimization of their hypolipidemic activities in recent years. However, so far there is no available quantitative structure–activity relationship (QSAR) model used for the development of novel BBR analogues with hypolipidemic activities, mainly due to lack of lipid‐lowering molecular mechanisms and target identification of BBR. In this paper, the tactics using ligand efficiency indice instead of pIC₅₀ as the activity could be adopted for the development of BBR QSAR models. A series of 59 BBR derivatives with hypolipidemic activities have been studied and split randomly into three sets of training and test sets. Statistical quality of most building models shows obviously robust. Best calculated model that employs LLE indice as the activity (Model 6 ) has the following statistical parameters: for training set R² = .984, Q² = 0.981, RMSE = 0.1160, and for test set R² = .989, RMSE = 0.0067. This model would be used for the development of novel BBR analogues with lipid‐lowering activities as a hit discovery tool.     

Interactions of putatively irreversible antagonists with beta 1- and beta 2-adrenergic receptors

Three compounds that have been suggested to irreversibly inactivate beta-adrenergic receptors were studied: NHNPNBE [N-(2-hydroxy-3-[1-napthoxy]-propyl)-N-bromoacetylethylenediami ne], BAAM (bromoacetylalprenololmenthane), and Ro 3-7894 [1-(5-chloracetylaminobenzfuran-2-yl)-2-isopropylaminoethanol++ +]. Membranes of rat cerebral cortex were used as a source of predominantly beta 1-adrenergic receptors and membranes of rat cerebellum were used as a source of predominantly beta 2-adrenergic receptors. Beta-Adrenergic receptor binding sites were studied by Scatchard analysis of saturation isotherms of specific [125I]-pindolol ([125I]PIN) binding. NHNPNBE added to the incubation medium competitively inhibited specific [125I]PIN binding in both cerebellum and cerebral cortex with KI values of 1-2 microM in each tissue. After washout of membranes pretreated with NHNPNBE for 30 min at 37 degrees, no loss of specific [125I]PIN binding sites was observed in either cerebellum or cortex except at very high concentrations (30-100 microM). Ro 3-7894 caused a simple competitive inhibition of specific [125I]PIN binding in rat cerebellar membranes with a KI of approximately 14 microM, an effect which was reversed completely by washing. In cerebral cortex, Ro 3-7894 added to the incubation medium apparently decreased the density of [125I]PIN binding sites with an IC50 around 1 microM. This effect was reversed after washing the membranes twice. However, in the presence of Ro 3-7894 some Scatchard plots showed a slight curvature. Further saturation of the [125I]PIN binding sites in cerebral cortex showed that the inhibition by Ro 3-7894 was competitive but with a high- and low-affinity component, consistent with Ro 3-7894 being a beta 1-selective competitive antagonist. Ro 3-7894 was also beta 1-selective in other tissues. BAAM added to the incubation medium competitively inhibited specific [125I]PIN binding in both cerebellum and cortex with KI values of 0.006 to 0.03 microM, but was about 5-fold more potent in cerebellum. After treatment of membranes with higher concentrations of BAAM for 30 min at 37 degrees and washing twice, there was a dose-dependent decrease in the density of specific [125I]PIN binding sites with IC50 values of approximately 0.3 microM in both tissues. Similar effects were observed in rat heart. These data suggest that NHNPNBE is a simple competitive antagonist at both beta 1- and beta 2-adrenergic receptors except at very high concentrations. Ro 3-7894 is a beta 1-selective competitive antagonist with no apparent irreversible effects.(ABSTRACT TRUNCATED AT 400 WORDS)     

Controversies in asthma therapy with theophylline and the beta 2-adrenergic agonists

The pharmacology and clinical use of the beta 2-adrenergic agonists and theophylline, singly and in combination, are reviewed. The beta 2-adrenergic agents produce bronchodilation by stimulating production of intracellular cyclic adenosine monophosphate, while theophylline's mechanism of action is unknown. The primary differences between various beta 2-adrenergic agents are in specificity and duration of action. In acute asthma attacks, greater reversal of bronchospasm results from beta 2-adrenergic agents than from theophylline. Inhalation of beta 2-adrenergic agents is as effective as injection of these drugs and produces fewer side effects. Inhaled beta 2-adrenergic agents also produce the greatest degree of prevention of exercise-induced bronchospasm. In hospitalized patients with severe acute bronchospasm, the combination of intravenous aminophylline and inhaled beta 2-adrenergic agents appears to provide optimal therapy with the greatest margin of safety. For long-term bronchodilator therapy, there is no clear treatment of choice; combination therapy with inhaled beta 2-adrenergic agents and oral theophylline appears to be safe and effective.     

Synthesis and beta 1-, beta 2-adrenergic receptor binding studies of 4-acylamino-substituted phenoxypropanolamine and 5-acylamino-substituted naphthyloxypropanolamine derivatives

The object of this study was to investigate the beta-adrenergic receptor binding affinity of 4-acylaminophenoxypropanolamine (10-15) and 5-acylaminonaphthyloxypropanolamine (21-24) derivatives, which were prepared from 4-aminophenol (5) and 5-amino-1-naphthol (16), respectively. The in vitro beta 1- and beta 2-adrenergic receptor binding affinities of the newly synthesized compounds were assessed in turkey erythrocyte membrane (beta 1) and lung homogenates of rats (beta 2). The binding affinities were compared with that of propranolol (3) (propranolol hydrochloride, CAS 318-98-9). The compound N-[5-(3-tert-butylamino-2-hydroxy-propoxy)-naphthalen-1-yl]-acetamide (22) has beta-adrenergic receptor affinity comparable with that of propranolol and shows selectivity to beta 1-adrenergic receptors.     

The role of beta(2)-adrenergic receptors in inflammation and allergy

Essential role of beta(2)-adrenoreceptor (beta(2)AR) in airway relaxation is well established. Nevertheless, beta(2)AR seems playing an actual role in allergy and inflammation. Interaction between beta(2)AR and proinflamatory cytokines in airway smooth muscle has been revealed. Being located on proinflamatory cells, beta(2)ARs may influence function of these cells in vivo. It was clear established, that stimulation of beta(2)AR inhibits release of proinflamatory mediators from mast cells, influences T-cell growth and function, eosinophil survival and function, including GM-CSF- or PAF-induced degranulation. Stimulation of beta(2)ARs, located on alveolar macrophages and epithelial cells, has ambiguity influence on their regulation and function, including phagocytosis and mediator secretion, in vivo. Vascular responses, resulting in inhibition of plasma exudation were confirmed, but modulation of sensory nerves via beta(2)AR is not certain yet. beta(2)AR-agonists are effective in treatment of immediate allergic reactions, but desensitisation of beta(2)ARs on inflammatory cells may result in paradoxical effects, especially in asthma. In summary, it is clear that beta(2)ARs may play an anti-inflammatory role in vitro. Unfortunately, in vitro data have shown limited applicability in vivo; therefore further research in this field is required.     

Identification of a beta 2-adrenergic receptor in mammalian epidermis

The presence of a beta₂-adrenergic receptor in the epidermis has been demonstrated, based on the following pieces of information: (1) the addition of salbutamol, a beta₂-agonist, to slices of epidermal tissue increased the levels of cyclic AMP in the tissue above control levels in a dose-dependent manner with a maximum response after 5 min of incubation in 5 × 10^?5 M salbutamol, (2) the addition of butoxamine, a beta₂-antagonist, in conjunction with isoproterenol or salbutamol reduced the epidermal cyclic AMP levels when compared to levels obtained with agonist alone, (3) practolol, a beta₁-antagonist. had little effect on the salbutamol-induced increases in the cyclic AMP levels and further elevated the levels of cyclic AMP obtained by the addition of isoproterenol, (4) the addition of propranolol to the tissue in conjunction with isoproterenol or salbutamol reduced the levels of cyclic AMP to near control values, and (5) Ro 20-1724, a cyclic nucleotide phosphodiesterase inhibitor, maintained the salbutamolelevated cyclic AMP levels for a longer period of time.     

Prediction of anti-HCV activity of thiourea derivatives: QSAR approach

Abstract  

In pursuit of more active thioureas as anti-HCV agent, QSAR studies were performed on a series of thioureas to explore the various physico-chemical parameters responsible for their activity against HCV-infected AVa 5 cell. Physico-chemical parameters were calculated using WIN CAChe 6.1. Stepwise multiple linear regression analysis was performed to derive QSAR models which were further evaluated for statistical significance and predictive power by internal and external validation. The selected best QSAR model was having correlation coefficient (R) = 0.902 and cross-validated squared correlation coefficient (Q ²) = 0.734. The developed significant QSAR model indicates that hydrophobicity, dielectric energy, valence connectivity index (order 1), and ionization potential of whole molecule play an important role in anti-HCV activity of thioureas. The hydrophobicity of thioureas was found to have parabolic relation with its anti-HCV activity. The optimum logP value for these anti-HCV compounds was found to be 4.988.     

Ion-pair liquid chromatographic assay of angiotensin-converting enzyme activity

A rapid and specific high-performance liquid chromatographic assay for the quantitative determination of angiotensin-converting enzyme activity is described. Hippuryl-L-histidyl-L-leucine (Hip-His-Leu) is used as substrate and the released hippuric acid is measured. The procedure is accurate and precise and no extraction is required.     

The third intracellular loop and the carboxyl terminus of beta2-adrenergic receptor confer spontaneous activity of the receptor

It is well established that the beta2-adrenergic receptor (beta2-AR) exhibits a robust ligand-independent activity, whereas this property is considerably weaker in the closely related beta1-AR subtype. To identify the potential domain(s) of beta2-AR responsible for the spontaneous receptor activation, we created three chimeras in which the third intracellular loop (beta1/beta2-Li3) or the carboxyl terminus (beta1/beta2-CT) or both domains (beta1/beta2-Li3CT) of beta1-AR are replaced by the corresponding parts of the beta2-AR. Using adenoviral gene transfer, we individually expressed these beta1/beta2-AR chimeras in mouse cardiomyocytes lacking both native beta1-AR and beta2-AR (beta1/beta2 double knockout), and examined their possible spontaneous activities. Overexpression of these beta1/beta2-AR chimeras markedly elevated basal cAMP accumulation and myocyte contractility in the absence of agonist stimulation compared with those infected by a control adenovirus expressing beta-galactosidase or an adenovirus expressing wild type beta1-AR. These effects were fully reversed by a beta2-AR inverse agonist, (+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol (ICI 118,551; 5 x 10-7 M), regardless of inhibition of Gi with pertussis toxin, but not by a panel of beta1-AR antagonists, including [2-(3-carbamoyl-4-hydroxyphenoxy)-ethylamino]-3-[4-(1-methyl-4-trifluormethyl-2-imidazolyl)-phenoxy]-2-propanolmethanesulfonate (CGP20712A), betaxolol, bisoprolol, and metoprolol. Furthermore, we have shown that the C-terminal postsynaptic density 95/disc-large/ZO-1 (PDZ) motif of beta1-AR is not responsible for the lack of beta1-AR spontaneous activation, although it has been known that the beta1-AR PDZ motif prevents the receptor from undergoing agonist-induced trafficking and Gi coupling in cardiomyocytes. Taken together, the present results indicate that both the third intracellular loop and the C terminus are involved in beta2-AR spontaneous activation and that either domain seems to be sufficient to confer the receptor spontaneous activity.     

Glycosyl derivatives of 2-bromosugar of selected non-steroidal anti-inflammatory drugs. Synthesis and QSAR data.

On the basis of molecular modeling and calculation of physicochemical SAR data we obtained new derivatives of 2-bromosugars 5a-d and 6 for widely used non-steroidal anti-inflammatory drugs (NSAIDs). Compounds 5a-d and 6 were synthesized as stable, crystalline compounds from the reaction of phosphoroates 1-3 with salicylic acid (4a), aspirin (4b), diclofenac (4c) and indomethacin (4d) in an aprotic solvent. The reaction took place in the presence of silver carbonate as the activator of leaving groups with high stereoselectivity and good yields. The structures of the new derivatives of 5a-d and 6 for NSAIDs were established by spectroscopic methods 1H and 13C NMR, and elemental analyses.     

Synthesis and biological evaluation of a tetrahydroisoquinoline derivative possessing selective beta2-adrenergic agonist activity.

This paper reports the synthesis of 4-(3,4,5-trimethoxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (2) and 2-(3,4-dihydroxyphenyl)-3-(3,4,5-trimethoxyphenyl)propylamine (3). The biological activity of these agents relative to that of trimetoquinol (1) in guinea pig atria and guinea pig trachea is reported. The relative activities in relaxation of guinea pig trachea is 1 greater than 2 greater than 3 while in the chronotropic response in guinea pig atria the relative order of activity is 1 greater than 3 greater than 2.     

Alpha 1-adrenergic stimulation and beta 2-adrenergic inhibition of DNA synthesis in vascular smooth muscle cells

Effects of catecholamines on DNA synthesis in vascular smooth muscle cells (VSMC) were investigated in a chemically defined medium that included insulin, transferrin, and sodium selenite. Smooth muscle-rich preparation was obtained from rat aortic media and VSMC were further purified by cell cloning. A clone that was positive for smooth muscle actin and was negative for the coagulation factor VIII was used in this study. The fetal calf serum-induced proliferation was enhanced by alpha-adrenergic and inhibited by beta-adrenergic stimulation. When cells of low passages were used, dose-response curves for norepinephrine were biphasic; when cells were subconfluent, norepinephrine stimulated DNA synthesis at as low as 1 nM and was apparently ineffective at more than 100 nM. When cells were confluent, the effect of norepinephrine was inhibitory at lower concentrations (less than 1 nM) and stimulatory at relatively higher concentrations. Cells of higher passages exhibited only inhibitory effects of the amine. Stimulatory and inhibitory effects on DNA synthesis were mediated through alpha 1- and beta 2-adrenergic receptors, respectively. Thus, the alpha 1-agonist phenylephrine was more potent than the alpha 2-agonist clonidine in stimulating DNA synthesis. An alpha 1-adrenergic antagonist, prazosin, was more effective than the alpha 2-adrenergic antagonist yohimbine in antagonizing the stimulatory effect of norepinephrine. beta-Adrenergic agonists inhibited DNA synthesis with IC50 values in the nanomolar range; the rank order of potency of agonists was isoproterenol greater than salbutamol greater than or equal to (-)-epinephrine much greater than (-)-norepinephrine, consistent with beta 2-receptor specificity. (+)-Epinephrine or (+)-norepinephrine, the stereoisomers of the catecholamines, were ineffective. The inhibitory effects of norepinephrine were reversed by beta-adrenergic antagonists, with the rank order of potency of pindolol greater than butoxamine greater than atenolol, consistent with beta 2-receptor specificity. The dose-response curves of norepinephrine, therefore, seemed to be determined by a balance between alpha 1-receptor-mediated stimulation and beta 2-receptor-mediated inhibition of DNA synthesis. Minimum time required for exhibiting alpha 1-adrenergic or beta 2-adrenergic effects was between 6 and 15 hr, suggesting that the G0 or G1 phase of the cell cycle might be the site of action. These results show that catecholamines dually modulate DNA synthesis in VSMC through specific adrenergic receptors.