Drug-receptor Interactions Research Articles

Target-directed screening of the bioactive compounds specifically binding to β₂-adrenoceptor in Semen brassicae by high-performance affinity chromatography.

The bioactive ingredients in Semen sinapis were rapidly screened by immobilized β2-adrenoceptor (β2-AR) and target-directed molecular docking. The methods involved the attachment of β2-AR using any amino group in the receptor, the simultaneous separation and identification of the retention compounds by high-performance affinity chromatography; the binding mechanism of the interesting compound to the receptor was investigated by zonal elution and molecular docking. Sinapine in Semen sinapis was proved to be the bioactive compound that specifically binds to the immobilized receptor. The association constant of sinapine to β2-AR was determined to be 1.36 × 10(5) M(-1) with a value of 1.27 × 10(-6) M for the number of binding sites. Ionic bond was believed to be the driving force during the interaction between sinapine and β2-AR. It is possible to become a powerful alternative for rapid screening of bioactive compounds from a complex matrix such as traditional Chinese medicine and further investigation on the drug-receptor interaction.

Development of selective DprE1 inhibitors: Design, synthesis, crystal structure and antitubercular activity of benzothiazolylpyrimidine-5-carboxamides

Decaprenylphosphoryl-b-d-ribose 20-epimerase (DprE1) is a potential drug target for development of antitubercular agents. Structure based drug discovery approach yielded twenty novel derivatives of benzothiazolylpyrimidine-5-carboxamides (7a–t) which were synthesised by three component one pot reaction involving benzothiazolyl oxobutanamide, thiourea and substituted aromatic benzaldehydes. These derivatives were evaluated for antitubercular activity to determine MIC and compound 7a, 7e, 7f and 7o were found to be potentially active against Mycobacterium tuberculosis (H37Rv). Log P of these compounds was found to be between 2.0 and 3.0 making them suitable for oral dosing. DprE1 selectivity and pharmacokinetic studies were carried out for these compounds of which 7a and 7o were found to be highly selective and bioavailability was found to be above 52% by oral dose. Crystal structure of 7a was studied and molecular packing was determined, it exhibited a triclinic crystal lattice arrangement having hydrogen bonded dimeric arrangement. Drug receptor interactions were studied which exhibited docking in the active site of receptor with hydrogen bonding, hydrophobic interactions, vdW interactions with amino acid residues such as Cys387, Asn385, Lys418, Tyr314, Gln334 and Lys367 respectively. 3D QSAR analysis was carried out by kNN-MFA method to determine and develop theoretical model, best suitable model was found to be based on Simulated Annealing k-Neariest Neighbour Molecular Field Analysis (SA kNN-MFA). The model provided with hydrophobic descriptors in positive side indicating the need of bulky groups, steric and electronegative descriptors in negative coordinates hints with contribution by the electronegative substitutions as favourable and desirable moieties for enhancing the activity. The q2, q2_se and Pred_r2se were found to be 0.5000, 0.6404 and 1.0094 respectively. A pharmacophore model was generated which suggested for necessity of aromatic, aliphatic carbon centre and hydrogen bond donor for development of newer DprE1 selective inhibitors.

Spectroscopic and quantum chemical analysis of a natural product – Hayatin hydrochloride

Majority of drugs in use today are natural products, natural product mimics or semi synthetic derivatives. Therefore in recent times, focus on plant research has increased all over the world and large body of evidence has been collected to show immense potential of medicinal plants used in various traditional systems. Therefore, in the present communication to aid that research, structural and spectroscopic analysis of a natural product, an alkaloid Hayatin hydrochloride was performed. Both ab initio Hartree–Fock and density functional theory employing B3LYP with complete relaxation in the potential energy surface using 6-311G (d,p) basis set were used for the calculations. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR and micro-Raman spectra. The complete assignments were performed on the basis of potential energy distribution. The structure–activity relationship has also been interpreted by mapping electrostatic potential surface, which are valuable information for the quality control of medicines and drug-receptor interactions. Electronic properties have been analysed employing TD-DFT for both gaseous and solvent phase. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis.

Analysis of Drug Interactions with Dopamine Receptor by Frontal Analysis and Cell Membrane Chromatography

Determining the interactions between drugs and receptors is very important in revealing the activity and mechanism of drugs. The dopamine receptor was purified from rat brain tissue and immobilized on the surface of silica gel to prepare the stationary phase. From the model of frontal analysis conducted with DAR/CMC columns, the dissociation equilibrium constants (K D) were (4.87 ± 0.35) × 10−6 M for dopamine, (5.58 ± 0.20) × 10−7 M for olanzapine, (5.22 ± 0.12) × 10−7 M for quetiapine, (4.50 ± 0.37) × 10−7 M for bupropion, and (3.41 ± 0.28) × 10−7 M for domperidone. The affinity order conducted by frontal analysis had a positive correlation with the k values of the antagonists. Competitive binding study showed that domperidone, bupropion, quetiapine and olanzapine occupied certain binding sites of DAR on the column, thus hindering the association of dopamine. In addition, hydrophobic interaction was the main force for domperidone, bupropion and dopamine to bind with DAR. For quetiapine and olanzapine, hydrogen bond or Van der Waals force is the major factor contributing to the interaction. The studies showed that CMC could be applied to the investigation of drug–receptor interactions.

ErbB polymorphisms: insights and implications for response to targeted cancer therapeutics.

Advances in high-throughput genomic-scanning have expanded the repertory of genetic variations in DNA sequences encoding ErbB tyrosine kinase receptors in humans, including single nucleotide polymorphisms (SNPs), polymorphic repetitive elements, microsatellite variations, small-scale insertions and deletions. The ErbB family members: EGFR, ErbB2, ErbB3, and ErbB4 receptors are established as drivers of many aspects of tumor initiation and progression to metastasis. This knowledge has provided rationales for the development of an arsenal of anti-ErbB therapeutics, ranging from small molecule kinase inhibitors to monoclonal antibodies. Anti-ErbB agents are becoming the cornerstone therapeutics for the management of cancers that overexpress hyperactive variants of ErbB receptors, in particular ErbB2-positive breast cancer and non-small cell lung carcinomas. However, their clinical benefit has been limited to a subset of patients due to a wide heterogeneity in drug response despite the expression of the ErbB targets, attributed to intrinsic (primary) and to acquired (secondary) resistance. Somatic mutations in ErbB tyrosine kinase domains have been extensively investigated in preclinical and clinical setting as determinants for either high sensitivity or resistance to anti-ErbB therapeutics. In contrast, only scant information is available on the impact of SNPs, which are widespread in genes encoding ErbB receptors, on receptor structure and activity, and their predictive values for drug susceptibility. This review aims to briefly update polymorphic variations in genes encoding ErbB receptors based on recent advances in deep sequencing technologies, and to address challenging issues for a better understanding of the functional impact of single versus combined SNPs in ErbB genes to receptor topology, receptor-drug interaction, and drug susceptibility. The potential of exploiting SNPs in the era of stratified targeted therapeutics is discussed.

A cell membrane chromatography method for screening 5-HT receptor agonists from drug pair of Chuanxiong Rhizoma and Angelicae Dahuricae Radix

Migraine is one of the common and frequently encountered diseases. The study proves that 5-hydroxytryptamine (5-HT) receptor, plays an important role in the occurrence of migraine. Rat striatum was used for preparation of the cell membrane stationary phase (CMSP) in our experiments. The cell membrane chromatography (CMC)-offline-HPLC system was applied to specifically recognize the components from the drug pair of Chuanxiong Rhizoma and Angelicae Dahuricae Radix, which interact with the receptors on CMSP. The dissociation equilibrium constant (KD) was measured in a rat striatum/CMC system, performed by continuously pumping sumatriptan, a 5-HT1D agonist, ranging from 2.42 x 10(-8) to 4.84 x 10(-7) mol · L(-1) through a CMC column, and the capacity factors (k') were recorded. The KD value obtained from the model was (4.59 ± 0.33) x 10(-6) mol · L(-1) for imperatorin, and the rat model of migraine induced by nitroglycerin was applied to validate the pharmacological effects of the drug pair. The results indicated that the CMC method could be a quick and efficient way for characterizing the drug-receptor interactions in vitro.

Spectral, thermal and kinetic studies of charge-transfer complexes formed between the highly effective antibiotic drug metronidazole and two types of acceptors: σ- and π-acceptors

Understanding the interaction between drugs and small inorganic or organic molecules is critical in being able to interpret the drug–receptor interactions and acting mechanism of these drugs. A combined solution and solid state study was performed to describe the complexation chemistry of drug metronidazole (MZ) which has a broad-spectrum antibacterial activity with two types of acceptors. The acceptors include, σ-acceptor (i.e., iodine) and π-acceptors (i.e., dichlorodicyanobenzoquinone (DDQ), chloranil (CHL) and picric acid (PA)). The molecular structure, spectroscopic characteristics, the binding modes as well as the thermal stability were deduced from IR, UV–vis, 1H NMR and thermal studies. The binding ratio of complexation (MZ: acceptor) was determined to be 1:2 for the iodine acceptor and 1:1 for the DDQ, CHL or PA acceptor, according to the CHN elemental analyses and spectrophotometric titrations. It has been found that the complexation with CHL and PA acceptors increases the values of enthalpy and entropy, while the complexation with DDQ and iodine acceptors decreases the values of these parameters compared with the free MZ donor.

A cell membrane chromatography method for investigation of 5-hydroxytryptamine receptor-ligustilide interaction

A rat striatum cell membrane chromatography (CMC) frontal analysis method was developed for the determination of the equilibrium dissociation constants (KD) for 5-hydroxytryptamine (5-HT) receptor 5-HT1D-ligustilide interactions. Rat striatum was used for preparation of the cell membrane stationary phase (CMSP). An enzyme-linked inmunosorbent assay (ELISA) was applied to determine the 5-HIT level of CMSP before and after the adsorption of cell membrane, and the value was (40.5 ± 2.3) pg per gram of silica. The CAIC-offline-HPLC system was applied to specifically recognize the mixed standard solution of sumatriptan and ligustilide. Sumatriptan, a 5-HT1D agonist of 24.2 to 242 nmol/L, was pumped through a CMC column continuously, and the breakthrough curves were recorded. For further competitive studies, the mobile phase that contained ligustilide (37.0-370 nmol/L) was pumped through the column to saturate the binding sites. Afterwards, sumatriptan was propelled towards the column. The breakthrough curves were recorded and compared with those obtained from the column without saturation. K(D), values obtained using frontal analysis were 389 nmol/L and 4.21 µmol/L for sumatriptan and ligustilide, respectively. The competitive binding study indicated that the CMC method could be a quick and efficient way for determining the K(D) values in drug-receptor interactions.

DRUG-RECEPTOR INTERACTIONS:IN SILICOAPPROACHES APPLIED TO EXPERIMENTAL CLASSES REGARDING THE EVOLUTION OF ANGIOTENSIN CONVERTING ENZYME INHIBITORS

Teaching classes and events regarding the molecular aspects of drug-receptor interactions is not an easy task. The ligand stereochemistry and the spatial arrangement of the macromolecular targets highly increase the complexity of the process. In this context, the use of alternative and more playful approaches could allow students to gain a more thorough understanding of this important topic in medicinal chemistry. Herein, we describe a practical teaching approach that uses computational strategies as a tool for drug-receptor interaction studies performed for angiotencsin converting enzyme inhibitors (ACEi). Firstly, the students learn how to find the crystallographic structure (enzyme-ligand complex). Then, they proceed to the treatment of crude crystallographic data. Thereafter, they learn how to analyze the positioning of the drug on the active site of the enzyme, looking for regions related to the molecular recognition. At the end of the study, students can summarize the molecular requirements for the interaction and the structure-activity relationships of the studied drugs.

Individual variation of human S1P1 coding sequence leads to heterogeneity in receptor function and drug interactions

Sphingosine 1-phosphate receptor 1 (S1P₁), an abundantly-expressed G protein-coupled receptor which regulates key vascular and immune responses, is a therapeutic target in autoimmune diseases. Fingolimod/Gilenya (FTY720), an oral medication for relapsing-remitting multiple sclerosis, targets S1P₁ receptors on immune and neural cells to suppress neuroinflammation. However, suppression of endothelial S1P₁ receptors is associated with cardiac and vascular adverse effects. Here we report the genetic variations of the S1P₁ coding region from exon sequencing of >12,000 individuals and their functional consequences. We conducted functional analyses of 14 nonsynonymous single nucleotide polymorphisms (SNPs) of the S1PR1 gene. One SNP mutant (Arg¹²⁰ to Pro) failed to transmit sphingosine 1-phosphate (S1P)-induced intracellular signals such as calcium increase and activation of p44/42 MAPK and Akt. Two other mutants (Ile⁴⁵ to Thr and Gly³⁰⁵ to Cys) showed normal intracellular signals but impaired S1P-induced endocytosis, which made the receptor resistant to FTY720-induced degradation. Another SNP mutant (Arg¹³ to Gly) demonstrated protection from coronary artery disease in a high cardiovascular risk population. Individuals with this mutation showed a significantly lower percentage of multi-vessel coronary obstruction in a risk factor-matched case-control study. This study suggests that individual genetic variations of S1P₁ can influence receptor function and, therefore, infer differential disease risks and interaction with S1P₁-targeted therapeutics.

In situ drug-receptor binding kinetics in single cells: a quantitative label-free study of anti-tumor drug resistance.

Many drugs are effective in the early stage of treatment, but patients develop drug resistance after a certain period of treatment, causing failure of the therapy. An important example is Herceptin, a popular monoclonal antibody drug for breast cancer by specifically targeting human epidermal growth factor receptor 2 (Her2). Here we demonstrate a quantitative binding kinetics analysis of drug-target interactions to investigate the molecular scale origin of drug resistance. Using a surface plasmon resonance imaging, we measured the in situ Herceptin-Her2 binding kinetics in single intact cancer cells for the first time, and observed significantly weakened Herceptin-Her2 interactions in Herceptin-resistant cells, compared to those in Herceptin-sensitive cells. We further showed that the steric hindrance of Mucin-4, a membrane protein, was responsible for the altered drug-receptor binding. This effect of a third molecule on drug-receptor interactions cannot be studied using traditional purified protein methods, demonstrating the importance of the present intact cell-based binding kinetics analysis.

Contributions of charge-density research to medicinal chemistry.

This article reviews efforts in accurate experimental charge-density studies with relevance to medicinal chemistry. Initially, classical charge-density studies that measure electron density distribution via least-squares refinement of aspherical-atom population parameters are summarized. Next, interaction density is discussed as an idealized situation resembling drug-receptor interactions. Scattering-factor databases play an increasing role in charge-density research, and they can be applied both to small-molecule and macromolecular structures in refinement and analysis; software development facilitates their use. Therefore combining both of these complementary branches of X-ray crystallography is recommended, and examples are given where such a combination already proved useful. On the side of the experiment, new pixel detectors are allowing rapid measurements, thereby enabling both high-throughput small-molecule studies and macromolecular structure determination to higher resolutions. Currently, the most ambitious studies compute intermolecular interaction energies of drug-receptor complexes, and it is recommended that future studies benefit from recent method developments. Selected new developments in theoretical charge-density studies are discussed with emphasis on its symbiotic relation to crystallography.

Investigation on the Binding of Terazosin Hydrochloride and Naftopidil to an Immobilized α 1-Adrenoceptor by Zonal Elution

The interaction between drugs and receptors is particularly important in revealing the drug acting mechanism and developing new leads. In this work, α1-Adrenoceptor (α1-AR) from HEK293 cell line is purified and immobilized on the surface of macro-pore silica gel to prepare an high-performance affinity chromatography stationary phase for the pursuit of drug–receptor interactions by competition zonal elution. Naftopidil is found to have only one type of binding site to α1-AR with an association constant of 1.45 × 106 M−1 and a concentration of binding sites of 1.56 × 10−6 M, while terazosin hydrochloride proves to present two kinds of binding site on the receptor at which the association constants are determined to be 1.61 × 105 M−1 and 2.06 × 103 M−1, and the corresponding concentrations of the binding sites are 1.56 × 10−6 M and 1.11 × 10−3 M, respectively. It is concluded that the stationary phase containing attached α1-AR can be used to realize the binding of a drug to the receptor.

Application of charge-transfer complexation for evaluation of the drug-receptor mechanism of interaction: Spectroscopic and structure morphological properties of procaine and pilocarpine complexes with chloranilic acid acceptor

Study of the charge-transfer or proton-transfer interaction of drugs is important for understanding the drug-receptor interactions and the mechanism of drug action. In the current research the corresponding data were accumulated in the course of synthesis and study of the H-bonded complexes originated from the interaction between procaine (Pro) or pilocarpine (Pil) drugs and chloranilic acid (CLA). The targeted microstructure products have been isolated and characterized by elemental and spectral (electronic and vibrational) data. Microstructural properties of the reported complexes were studied with XRD and SEM techniques. The Pil drug containing complex exhibited a specific electronic spectrum with a strong, broad absorption band with much longer wavelength, λmax, than those typical for the individual reagents. It is noteworthy that the complex had good crystallinity. Application of Debye-Scherrer equation indicated that the reported complexes were in the range of nanosize.

Recent advances in cell membrane chromatography for traditional Chinese medicines analysis

Traditional Chinese medicines (TCMs) have been used for preventative care for thousands of years. The active components are the basis for the pharmacodynamics of TCMs, and they can be an important source of lead compounds. As a bioaffinity chromatography technique, cell membrane chromatography (CMC) has been developed for almost 20 years since 1996. It has been proven to be a useful method for studying drug–receptor interactions and screening active components from medicinal herbs. In our review in 2007 (Drug Discov. Ther., 1 (2007) 104–107), the preparation, identification, evaluation, and preliminary applications of CMC stationary phases were presented. In this article, we briefly review some of the latest progress and applications about CMC including instrument development, research on drug–receptor interactions, screening active components from TCMs, and quality control of TCMs.

Designing of Sulfanilamide/Sulfacetamide Derivatives as Human Topoisomerase II Inhibitor: A Docking Approach

Diseases characterized by out-of-control cell growth are known as cancer. One of the most important mechanisms for handling it is the inhibition of the human topoisomerase II receptor. In same context while studying the treatment of cancer we found the significant effects of the derivatives of the sulfonamides, this promotes us to design novel derivatives by the means of in-silico resources with anticancer effects. Molecular docking approaches are routinely used in modern drug design to help understand drug–receptor interaction. This study has been performed with the help of Chemdraw Ultra 7.0, AutoDock Vina (Python Prescription 0.8), and PaDEL software. Results revealed that ligand-protein interaction affinity of all 12 designed molecules ranges from -6.8 Kcal/mol to -8.6 Kcal/mol which is approximately comparable to pre-existing human topoisomerase II inhibitor i.e. etoposide (CID: 36462, ligand-protein interaction affinity is -9.7 Kcal/mol).

Comparative normal/failing rat myocardium cell membrane chromatographic analysis system for screening specific components that counteract doxorubicin-induced heart failure from Acontium carmichaeli.

Cell membrane chromatography (CMC) derived from pathological tissues is ideal for screening specific components acting on specific diseases from complex medicines owing to the maximum simulation of in vivo drug-receptor interactions. However, there are no pathological tissue-derived CMC models that have ever been developed, as well as no visualized affinity comparison of potential active components between normal and pathological CMC columns. In this study, a novel comparative normal/failing rat myocardium CMC analysis system based on online column selection and comprehensive two-dimensional (2D) chromatography/monolithic column/time-of-flight mass spectrometry was developed for parallel comparison of the chromatographic behaviors on both normal and pathological CMC columns, as well as rapid screening of the specific therapeutic agents that counteract doxorubicin (DOX)-induced heart failure from Acontium carmichaeli (Fuzi). In total, 16 potential active alkaloid components with similar structures in Fuzi were retained on both normal and failing myocardium CMC models. Most of them had obvious decreases of affinities on failing myocardium CMC compared with normal CMC model except for four components, talatizamine (TALA), 14-acetyl-TALA, hetisine, and 14-benzoylneoline. One compound TALA with the highest affinity was isolated for further in vitro pharmacodynamic validation and target identification to validate the screen results. Voltage-dependent K+ channel was confirmed as a binding target of TALA and 14-acetyl-TALA with high affinities. The online high throughput comparative CMC analysis method is suitable for screening specific active components from herbal medicines by increasing the specificity of screened results and can also be applied to other biological chromatography models.

Safety, tolerability, and pharmacokinetic evaluation of single‐ and multiple‐ascending doses of a novel kappa opioid receptor antagonist LY2456302 and drug interaction with ethanol in healthy subjects

Accumulating evidence indicates that selective antagonism of kappa opioid receptors may provide therapeutic benefit in the treatment of major depressive disorder, anxiety disorders, and substance use disorders. LY2456302 is a high-affinity, selective kappa opioid antagonist that demonstrates >30-fold functional selectivity over mu and delta opioid receptors. The safety, tolerability, and pharmacokinetics (PK) of LY2456302 were investigated following single oral doses (2-60 mg), multiple oral doses (2, 10, and 35 mg), and when co-administered with ethanol. Plasma concentrations of LY2456302 were measured by liquid chromatography-tandem mass spectrometry method. Safety analyses were conducted on all enrolled subjects. LY2456302 doses were well-tolerated with no clinically significant findings. No safety concerns were seen on co-administration with ethanol. No evidence for an interaction between LY2456302 and ethanol on cognitive-motor performance was detected. LY2456302 displayed rapid oral absorption and a terminal half-life of approximately 30-40 hours. Plasma exposure of LY2456302 increased proportionally with increasing doses and reached steady state after 6-8 days of once-daily dosing. Steady-state PK of LY2456302 were not affected by coadministration of a single dose of ethanol. No clinically important changes in maximum concentration (Cmax ) or AUC of ethanol (in the presence of LY2456302) were observed.

Functional Probes of Drug–Receptor Interactions Implicated by Structural Studies: Cys-Loop Receptors Provide a Fertile Testing Ground

Structures of integral membrane receptors provide valuable models for drug–receptor interactions across many important classes of drug targets and have become much more widely available in recent years. However, it remains to be determined to what extent these images are relevant to human receptors in their biological context and how subtle issues such as subtype selectivity can be informed by them. The high precision structural modifications enabled by unnatural amino acid mutagenesis on mammalian receptors expressed in vertebrate cells allow detailed tests of predictions from structural studies. Using the Cys-loop superfamily of ligand-gated ion channels, we show that functional studies lead to detailed binding models that, at times, are significantly at odds with the structural studies on related invertebrate proteins. Importantly, broad variations in binding interactions are seen for very closely related receptor subtypes and for varying drugs at a given binding site. These studies highlight the essential interplay between structural studies and functional studies that can guide efforts to develop new pharmaceuticals.

Nano-structured complexes of reserpine and quinidine drugs with chloranilic acid based on intermolecular H-bond: Spectral and surface morphology studies

The study of the drug-acceptor interaction may be useful in understanding the drug-receptor interactions and the mechanism of drug action. Here, complexes of reserpine (Res) and quinidine (Qui) drugs with chloranilic acid (CLA) have been synthesized. Then, these complexes were characterized chemically and structurally using CHN elemental analysis, infrared (IR) and electronic absorption spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The stoichiometry of the H-bonded complex was found to have a 1:1 ratio, so these complexes can be formulated as [(Drug)(CLA)]. IR measurements confirmed the presence of intermolecular H-bond. Application of Debye–Scherrer equation indicates that the formed complexes are in the range of nano-size. The Res complex exhibits a remarkable crystalline morphology. It was also found that the particle size of Res complex is 1.533 time higher than that of Qui complex. Interestingly, free Res molecular weight is higher than that of free Qui by the same ratio (precisely; 1.525).