Development of novel ß2-adrenergic receptor agonists for the stimulation of glucose uptake - The importance of chirality and ring size of cyclic amines.

ß2-Adrenergic receptor (ß2AR) agonists have been reported to stimulate glucose uptake (GU) by skeletal muscle cells and are therefore highly interesting as a possible treatment for type 2 diabetes (T2D). The chirality of compounds often has a great impact on the activity of ß2AR agonists, although this has thus far not been investigated for GU. Here we report the GU for a selection of synthesized acyclic and cyclic ß-hydroxy-3-fluorophenethylamines. For the N-butyl and the N-(2-pentyl) compounds, the (R) and (R,R) (3d and 7e) stereoisomers induced the highest GU. When the compounds contained a saturated nitrogen containing 4- to 7-membered heterocycle, the (R,R,R) enantiomer of the azetidine (8a) and the pyrrolidine (9a) had the highest activity. Altogether, these results provide pivotal information for designing novel ß2AR agonist for the treatment of T2D.

Antiasthmatic Compounds Targeting ß2-Adrenergic Receptor from Perilla frutescens Improved Lung Inflammation by Inhibiting the NF-κB Signaling Pathway.

Asthma is a highly prevalent and heterogeneous chronic respiratory disease and is often treated with inhaled corticosteroids or in combination with a ß2-adrenergic receptor (ß2-AR) agonist. However, around 5% of asthma remains uncontrolled, and more effective antiasthmatic drugs with known mechanisms are in high demand. Herein, we immobilized ß2-AR on the polystyrene amino microsphere surface in a one-step fashion. The successful immobilization of ß2-AR was verified by scanning electron microscopy and chromatographic analysis. We screened rosmarinic acid (RA) as the bioactive compound targeting ß2-AR in Perilla frutescens (L.) Britton by mass spectroscopy. The binding constant between RA and ß2-AR was determined to be 2.95 × 104 M-1 by adsorption energy distribution and frontal analysis. The antiasthmatic effect and mechanism of RA were examined on a murine model of allergic asthma induced by ovalbumin (OVA) and aluminum hydroxide. The results showed that RA significantly reduced lung inflammatory cell numbers, the production of Th2 cytokines, and the secretion of total IgE, OVA-specific IgE, and eotaxin. The decreased inflammatory cell infiltration and mucus hypersecretion were associated with the inhibition of the NF-κB signaling pathway. Moreover, the mRNA expression levels of AMCase, CCL11, CCR3, Ym2, and E-selectin in the lung tissues were effectively reduced. It is the first time that RA was proven to target ß2-AR and be effective in counteracting allergic airway inflammation via the NF-κB signaling pathway. Therefore, the immobilized ß2-AR preserves the potential in screening antiasthmatic compounds from herbal medicine, and RA can be developed as an effective agent for the treatment of allergic asthma.

Design, synthesis and biological evaluation of 8-(2-amino-1-hydroxyethyl)-6-hydroxy-1,4-benzoxazine-3(4H)-one derivatives as potent ß2-adrenoceptor agonists.

A series of ß2-adrenoceptor agonists with an 8-(2-amino-1-hydroxyethyl)-6-hydroxy-1,4-benzoxazine-3(4H)-one moiety is presented. The stimulatory effects of the compounds on human ß2-adrenoceptor and ß1-adrenoceptor were characterized by a cell-based assay. Their smooth muscle relaxant activities were tested on isolated guinea pig trachea. Most of the compounds were found to be potent and selective agonists of the ß2-adrenoceptor. One of the compounds, (R)-18c, possessed a strong ß2-adrenoceptor agonistic effect with an EC50 value of 24 pM. It produced a full and potent airway smooth muscle relaxant effect same as olodaterol. Its onset of action was 3.5 min and its duration of action was more than 12 h in an in vitro guinea pig trachea model of bronchodilation. These results suggest that (R)-18c is a potential candidate for long-acting ß2-AR agonists.

The determination of ß-agonist residues in bovine tissues using liquid chromatography-tandem mass spectrometry.

We aimed to develop a rapid, simple and reproducible method based on LC-tandem mass spectrometry (LC-MS/MS) to analyze ß-agonist residues (clenbuterol, zilpaterol, ractopamine and isoxsuprine) in bovine tissues. The method was validated in accordance with the European Council Decision 2002/657/EC. The samples were homogenized, and then 10 mL of an acetate buffer was added to a 5-g sample. The sample was then centrifuged at 12,000 rpm and filtered. Sodium hydroxide (2 m) was added to adjust pH of the sample that was centrifuged again. The extract was filtered through a solid-phase extraction column. The residue was re-dissolved in 250 µL acetonitrile and then subjected to LC-MS/MS. The separation was done on a C18 column. The mobile phase consisted of 0.1% formic acid in deionized water and 0.1% formic acid in methanol. The mean recoveries of ß-agonists were in the range of 84.3%-119.1% with relative standard deviations (%RSDs) of 0.683%-4.05%. Decision limits and detection capabilities of the analytes ranged from 0.0960 to 4.9349 µg/kg and from 0.0983 to 5.0715, respectively. This method was used to detect four ß-agonists in 100 bovine muscle, 100 liver and 100 kidney tissues from a slaughterhouse. No residue was found above the maximum residue limit level.

Cold Flow Evaluation in Transdermal Drug Delivery Systems by Measuring the Width of the Oozed Adhesive.

The objective of this study was to develop a simpler and more practical quantitative evaluation method of cold flow (CF) in transdermal drug delivery systems (TDDSs). CF was forcibly induced by loading a weight on a punched-out sample (bisoprolol and tulobuterol tapes). When the extent of CF was analyzed using the area of oozed adhesive as following a previously reported method, the CF profiles were looked different between the samples 12 mm in diameter subjected to a 0.5-kg weight and samples 24 mm in diameter subjected to a 2.0-kg weight despite an equal load per unit area (4.42 g/mm2). The width of oozed adhesive around the original sample was suggested to be an index that properly describes the relationship between the load per unit area and the extent of CF. Further, it was clarified that the average CF width over the entire circumference of the sample was the same whether the samples were round or square as long as the sample area and load were the same. We also observed a linear relationship between the CF width and the aspect ratio of oval and rectangular samples. These results indicated that the CF properties of typical TDDS products lacking CF-proof processing at the edges could be determined by testing samples cut from the product rather than the whole TDDS patch. The proposed width measuring method was simple and useful for optimizing the composition of the adhesive and for testing the quality of the product.

Hydrophobic deep eutectic solvent-based dispersive liquid-liquid microextraction for the simultaneous enantiomeric analysis of five ß-agonists in the environmental samples.

In this study, a simple and effective method was developed for the enantiomeric analysis of five ß-agonists (terbutaline, clorprenaline, tulobuterol, clenbuterol, and salbutamol) in water samples using deep eutectic solvent (DES) based dispersive liquid-liquid microextraction and chiral LC-MS. In such a framework, different kinds of hydrophobic DESs were tailored to examine their extraction ability for five ß-agonists from aqueous sample. After an initial screening, the primary factors affecting the extraction recovery of DES based dispersive liquid-liquid microextraction, such as hydrogen-bond acceptor/hydrogen-bond donor ratio, DES volume, type and volume of disperser solvent and so on, were investigated and optimized. Finally, the established method was validated and found to be linear, precise, and accurate. The method was successfully applied to analyze the five ß-agonists in water samples, which will help better understand the behavior of individual enantiomer and make accurate risk assessment on the ecosystem.

Photoelectrochemical determination of ractopamine based on inner filter effect between gold nanoparticles and graphitic carbon nitride-copper(II) polyphthalocyanine coupled with 3D DNA stabilizer.

Copper(II) polyphthalocyanine (CuPPc) was combined with graphitic carbon nitride (g-C3N4) to form a heterojunction with enhanced photoelectrochemical (PEC) signal. A sensitive PEC method was developed for determination of ractopamine based on a PEC inner filter effect between gold nanoparticles (AuNPs) and the g-C3N4/CuPPc. A gold electrode was modified with g-C3N4/CuPPc and the DNA was linked to the AuNPs. Initially, the PEC signal is weak due to the inner filter effect between the AuNPs and g-C3N4/CuPPc. In the presence of ractopamine, it interacts with the aptamer and the complementary chain (C chain) is released. This triggers the entropy-driven cyclic amplification and results in the release of the substrate B chain (SB chain) from three-dimensional DNA stabilizer. The probe is released from the electrode due to the interaction of probe DNA and the SB chain. As a result, the PEC signal increases linearly in the 0.1 pmol·L-1 to 1000 pmol·L-1 ractopamine concentration range. The detection limit is 0.03 pM, and the relative standard deviation is 3.4% (at a 10 pmol·L-1 level; for n = 11). The method has been successfully applied to the determination of ractopamine in pork samples. Graphical abstract Schematic presentation of detection method based on PEC inner filter effect between AuNPs and the g-C3N4/CuPPc being fabricated for ractopamine. 3D DNA was used as stabilizer to decrease the PEC blank signal.

Visualization and colorimetric determination of clenbuterol in pork by using magnetic beads modified with aptamer and complementary DNA as capture probes, and G-quadruplex/hemin and DNA antibody on the metal-organic framework MIL-101(Fe) acting as a peroxidase mimic.

A visualization strategy is described for the detection of clenbuterol (CLB). It is using of antibody against dsDNA and G-quadruplex/hemin labeled on a metal organic framework of type MIL-101(Fe) (G-quadruplex/hemin-anti-DNA/MIL-101) acting as a peroxidase mimetic, and magnetic beads modified with aptamer and complementary DNA (MB/Apt-cDNA) as capture probes. The detection reagent was prepared via the reactions between the double stranded DNA (Apt-cDNA) in capture probes and anti-DNA in peroxidase mimetic. In the presence of CLB, the aptamer on the magnetic beads preferentially binds CLB, and the peroxidase mimetic is released to the supernatant after magnetic separation. The released peroxidase mimetic can catalyze the TMB/H2O2 chromogenic system under mild conditions. This leads to the development of a blue-green coloration whose absorbance is measured at 650 nm. The detection limit is as low as 34 fM of CLB. The method was applied to the determination of CLB in pork samples and gave results that were consistent with data obtained with an ELISA kit. Graphical abstract A visualization strategy is described for the detection of clenbuterol. The selectivity of detection system for clenbuterol is excellent compared with other interferents. The method was applied to the determination of CLB in pork samples.

The synthesis of isotopologues of AZD7307: A selective ß2 -adrenoreceptor agonist.

A medicinal chemistry program to develop potent and selective LABA compounds required the synthesis of both carbon-14 and stable-isotope labelled materials.  Carbon-14 labelled AZD7307 was successfully synthesised in 6 steps from [14C]chloroacetyl chloride in an overall radiochemical yield of 10%. In addition, the synthetic route of a stable labelled isotopomer of AZD7307 is also described and synthesised in four linear steps from [13C6]cyclohexylamine hydrochloride in an overall yield of 12%.

Development of a highly sensitive and specific monoclonal antibody based enzyme-linked immunosorbent assay for the detection of a new ß-agonist, phenylethanolamine A, in food samples.

BACKGROUND: All ß-agonists are banned as feed additives for growth promotion in animals due to toxic effects on humans after consuming the ß-agonist contaminated meats. Phenylethanolamine A (PA) is a newly emerged ß-agonist. Thus there is a need to develop highly sensitive and specific analytical methods for the detection of PA in food samples. In this study, the monoclonal antibody (mAb) against PA was produced by hybridoma technology and used for the development of enzyme-linked immunosorbent assay (ELISA). RESULTS: The IC50 values and limits of detection (LODs) of the ELISA using homogeneous combination of coating antigen/antibody for PA were 0.16 ng mL-1 and 0.011 ng mL-1 , respectively. The cross-reactive (CR) values of the assay with 14 structurally related ß-agonists were lower than 0.59%. Swine liver and meat samples were spiked with PA at different content and analysed by ELISA. Acceptable recovery rates of 91.40-105.51% and intra-assay coefficients of variation of 1.56-9.92% (n = 3) were obtained. The ELISA for seven spiked samples was confirmed by LC-MS/MS with a high correlation coefficient of 0.9881. CONCLUSION: The proposed mAb-based ELISA was highly sensitive and specific for PA and could be used as a quantitative/screening method for PA analysis in food samples. © 2016 Society of Chemical Industry.

Efficient synthesis of D6 -clenproperol and D6 -cimaterol using deuterium isopropylamine as labelled precursor.

This report presents an efficient synthesis of D6 -clenproperol and D6 -cimaterol with 99.5% and 99.7% isotopic abundance in acceptable yields and excellent chemical purities with deuterium isopropylamine as labelled precursor. Their structures and the isotope-abundance were confirmed by proton nuclear magnetic resonance and liquid chromatography-mass spectrometry.

Determination of a large set of ß-adrenergic agonists in animal matrices based on ion mobility and mass separations.

While the coupling of traveling wave ion mobility spectrometry (TWIMS) and mass spectrometry is mainly reported for structural purposes, we studied its potential in enhancing compounds analysis such as growth promoters used in livestock animals at trace concentrations. ß-Adrenergic agonists have been selected as model compounds since they exhibit a range of close physicochemical properties leading to analytical issues using classical approaches. In this paper, the potential of Synapt G2-S (Q-TWIM-TOF MS) has been investigated for sensitive and specific detection of a range of these synthetic phenethanolamines in various complex biological matrices (retina, meat, and urine) from bovine considered as relevant in the context of detecting ß-adrenergic agonists use in animals. In particular, the specificity of the additional information provided by the TWIMS (i.e., collision cross section) together with the interest of the extra dimension of separation is discussed.

Determination of beta-agonists in swine hair by µFIA and chemiluminescence.

ß-Agonists are a group of illegal feed additives. In this paper, it was found that the light emission produced by the oxidation of luminol by potassium ferricyanide was enhanced by the ß-agonists (ractopamine, salbutamol, and terbutaline). Based on chemiluminescence phenomenon, a novel, rapid, and sensitive microflow injection analysis system on a microfluidic glass chip was established for determination of the ß-agonists. The chip was fabricated from two glass plates (64 mm × 32 mm) with microchannels of 200 µm width and 100 µm depth. The detection limits were achieved at 2.0 × 10(-8) mol/L of ractopamine, 1.0 × 10(-8) mol/L of terbutaline and 5.0 × 10(-7) mol/L of salbutamol. In this report, our method was applied for determination of the ß-agonists in swine hair from three different sources with satisfactory results.

Trantinterol, a novel ß2-adrenoceptor agonist, noncompetitively inhibits P-glycoprotein function in vitro and in vivo.

P-glycoprotein (P-gp)-mediated drug-drug interactions are important factors causing adverse effects of drugs in clinical use. The aim of this study was to determine whether trantinterol (also known as SPFF), a novel ß2-adrenoceptor agonist, was a P-gp inhibitor or substrate. The results showed that trantinterol was not a substrate of P-gp but increased rhodamine 123 (Rho 123) uptake by MDCK-MDR1 cells and decreased the efflux transport of both Rho 123 and cyclosporine A (CsA) in bidirectional transport studies across MDCK-MDR1 cell monolayers. This suggested that trantinterol was a P-gp inhibitor but not a P-gp substrate. The mechanism of inhibition was investigated in the P-gp-Glo assay system, where it was found that trantinterol inhibited P-gp ATPase activity in a dose-dependent manner. A subsequent study using the antibody binding assay with the conformation-sensitive P-gp-specific antibody UIC2 confirmed that trantinterol decreased UIC2 binding at 10 µM in contrast to the competitive inhibitor, verapamil. This suggested that trantinterol was a noncompetitive inhibitor of P-gp. Finally, a pharmacokinetic study in rat showed that trantinterol significantly increased the area under the plasma concentration-time curve (AUC) and maximum plasma concentration (Cmax) of digoxin and paclitaxel (PAC), and the Cmax of cyclosporine A (CsA). In summary, trantinterol is a potent noncompetitive P-gp inhibitor which may increase the bioavailability of other P-gp substrate drugs coadministered with it.

Agonist binding by the ß2-adrenergic receptor: an effect of receptor conformation on ligand association-dissociation characteristics.

The ß2-adrenergic receptor (ß2-AR), a G protein-coupled receptor (GPCR), is a physiologically important transmembrane protein that is a target for drugs used for treatment of asthma and cardiovascular diseases. Study of the first steps of ligand recognition and the molecular basis of ligand binding to the orthosteric site is essential for understanding the pharmacological properties of the receptor. In this work we investigated the characteristic features of the agonist association-dissociation process to and from the different conformational forms of ß2-AR by use of advanced molecular modeling techniques. The investigation was focused on estimating the free energy profiles (FEPs) corresponding to the process of a full agonist ((R,R)-fenoterol) and an inverse agonist (carazolol) binding and unbinding to and from ß2-AR. The two different conformational forms of ß2-AR, i.e. active ß2-AR-PDB: 3P0G and inactive ß2-AR-PDB: 2RH1 were included in this stage of the study. We revealed several significant qualitative differences between FEPs characteristic of both conformational forms. Both FEPs suggest the existence of three transient binding sites in the extracellular domain of ß2-AR. Comparison of the residues surrounding these transient binding sites in both ß2-AR states revealed the importance of the aromatic residues F194, H93(2.64), H296(6.58), and H178 (extracellular part of ß2-AR) in the early stages of the binding process. In addition, slightly different exit and entry paths are preferred by the ligand molecule in the extracellular part of ß2-AR, depending on the conformation of the receptor.

Assessing the clinical value of fast onset and sustained duration of action of long-acting bronchodilators for COPD.

The long-acting inhaled bronchodilators available for use in chronic obstructive pulmonary disease (COPD) vary in their pharmacological class (ß2-adrenergic agonist or antimuscarinic/anticholinergic, alone or combined), durations of action and speed of onset of bronchodilator effect. In the early stages of development of a maintenance bronchodilator, the goals are to identify a molecule with the theoretically 'ideal' profile of fast onset and prolonged duration of action in comparison with existing agents, while minimizing non-specific activity at organs outside the lungs. The move towards increasing duration of bronchodilator action is generally paralleled by improved effects on clinical outcomes, and the advent of more potent agents seems likely to provide an opportunity to reduce overreliance on the use of inhaled corticosteroids in treating COPD. In terms of onset of action, an immediately perceived benefit in reducing dyspnea, although not definitively demonstrated, might prove useful in increasing adherence, which is very poor among patients with COPD. Once-daily administration may also be helpful in this respect. Shared decision-making between patient and physician in the choice of treatment is important in optimizing adherence and, thus, treatment effectiveness.

Higenamine 4'-O-ß-d-glucoside in the lotus plumule induces glucose uptake of L6 cells through ß2-adrenergic receptor.

Hypoglycemic effect is an efficient means to modulate elevated blood glucose levels in patients with diabetes. We found that the extract of lotus plumule (the germ of Nelumbo nucifera Gaertn. seed) showed potent glucose uptake enhancement activity against L6 myotubes, which results in a hypoglycemic effect. This activity was further investigated, and an active constituent was identified as a single bioactive compound, higenamine 4'-O-ß-d-glucoside. Mechanistic studies employing phosphatidylinositol 3-kinase (PI3K) inhibitor, AMP-activated protein kinase (AMPK) inhibitor, or adrenergic receptor antagonist showed that the compound induced its activity through ß2-adrenergic receptor. Patients with type II diabetes mellitus frequently develop insulin resistance. Owing to the differences between the mechanism of action of insulin and of the isolated compound, the compound or lotus plumule itself may have the possibility of modulating blood glucose levels in insulin-resistant patients effectively.

Studies on binding interactions between clenbuterol hydrochloride and two serum albumins by multispectroscopic approaches in vitro.

In this study, binding properties of clenbuterol hydrochloride (CL) with human serum albumin (HSA) and bovine serum albumin (BSA) were examined using constant protein concentrations and various CL contents under physiological conditions. The binding parameters were confirmed using fluorescence quenching spectroscopy at various temperatures. The experimental results confirmed that the quenching mechanisms of CL and HSA/BSA were both static quenching processes. The thermodynamic parameters, namely, enthalpy change (ΔH) and entropy change (ΔS), were calculated according to the van't Hoff equation, which suggested that the electrostatic interactions were the predominant intermolecular forces in stabilizing the CL-HSA complex, and hydrogen bonds and van der Waals force were the predominant intermolecular forces in stabilizing the CL-BSA complex. Furthermore, the conformational changes of HSA/BSA in the presence of CL were determined using the data obtained from three-dimensional fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy and circular dichroism spectroscopy.

Enantioselective disposition of clenbuterol in rats.

Clenbuterol is a long-acting ß2-adrenoceptor agonist and bronchodilator that is used for the treatment of asthma, but the desired activities reside almost exclusively in the (-)-R-enantiomer. This study examined enantioselectivity in the disposition of clenbuterol following administration of clenbuterol racemate to rats. Concentrations of clenbuterol enantiomers in plasma, urine and bile were determined by LC-MS/MS assay with a Chirobiotic T column. This method was confirmed to show high sensitivity, specificity and precision, and clenbuterol enantiomers in 0.1 ml volumes of plasma were precisely quantified at concentrations as low as 0.25 ng/ml. The pharmacokinetic profiles of clenbuterol enantiomers following intravenous and intraduodenal administration of clenbuterol racemate (2 mg/kg) in rats were significantly different. The distribution volume of (-)-R-clenbuterol (9.17 l/kg) was significantly higher than that of (+)-S-clenbuterol (4.14 l/kg). The total body clearance of (-)-R-clenbuterol (13.5 ml/min/kg) was significantly higher than that of the (+)-S-enantiomer (11.5 ml/min/kg). An in situ absorption study in jejunal loops showed no difference in the residual amount between the (-)-R- and (+)-S-enantiomers. Urinary clearance was the same for the two enantiomers, but biliary excretion of (-)-R-clenbuterol was higher than that of the (+)-S-enantiomer. The fractions of free (non-protein-bound) (-)-R- and (+)-S-clenbuterol in rat plasma were 48.8% and 33.1%, respectively. These results indicated that there are differences in the distribution and excretion of the clenbuterol enantiomers, and these may be predominantly due to enantioselective protein binding.

ß3-Adrenoceptor-mediated responses in diabetic rat heart.

ß3-adrenoceptors mediate negative inotropic effect in contrast to classical ß1- and ß2-adrenoceptors. Cardiac ß3-adrenoceptors are upregulated in experimental diabetes. Thus, cardiodepressant effect mediated by ß3-adrenoceptors has been proposed to contribute to the impaired cardiac function in this pathology. In our study, we investigated the influence of streptozotocin-diabetes on cardiac contractility to ß3-adrenoceptors stimulation by using Langendorff-perfused rat hearts. BRL 37344, a selective ß3-adrenoceptor agonist, induced dose-dependent decreases in left ventricular developed pressure (LVDP) in hearts from control rats. BRL 37344 also dose-dependently decreased +dP/dt and -dP/dt values. Effects of BRL 37344 were abolished by SR 59230, but not altered by nadolol pre-treatment. On the other hand, these effects of BRL 37344 were all significantly increased in hearts from diabetic rats. We also observed that diabetes significantly increased the mRNA levels encoding cardiac ß3-adrenoceptors. In addition, Giα2 mRNA expressions were found to be increased in the cardiac tissue of diabetic rats as well. The effect of BRL 37344 on cardiac contractility was normalized upon treatment of diabetic rats with insulin. These data demonstrate an increased effect of ß3-adrenoceptor stimulation on hemodynamic function of the heart in accordance with an increased mRNA levels encoding cardiac ß3-adrenoceptors in 8-week diabetic rats.