Ligand and Structure Based Models for the Identification of Beta 2 Adrenergic Receptor Antagonists.

Ligand bound beta 2 adrenergic receptor (ß2AR) crystal structures are in use for screening of compound libraries for identifying inducers and blockers. However, in case of G protein coupled receptors (GPCR), docking and binding energy (BE) calculations are not enough to discriminate agonist and antagonists. Absence of a reliable model for discriminating ß2AR antagonist is still a major hurdle. Docking of known antagonists and agonists into activated and ground state ß2AR revealed several key intermolecular interactions and H-bonding patterns, which in combination, emerged as a model for prediction of antagonists. Present study identifies an alternative binding orientation, within the binding pocket, for blockers and a minimum grid size to lessen the false positive predictions. Cluster analysis revealed structural variability among the antagonists and a conserved pattern in case of agonists. A combination of docking and structure activity relationship (SAR) model reliably discriminated antagonists. Based on key intermolecular interactions, a set of agonists and antagonists useful to SAR, quantitative structure activity relationship (QSAR) and pharmacophore modeling, has also been proposed for identifying antagonists.

Prilocaine hydrochloride protects zebrafish from lethal effects of ionizing radiation: role of hematopoietic cell expansion.

Drug repositioning is an approach of significant translatability, and the present study was undertaken to screen a collection of FDA approved small-molecule clinical compounds for identification of novel radioprotective agents. Screening of JHCCL (Johns Hopkins Clinical Compound Library), a collection of 1,400 FDA approved small molecules, lead to identification of prilocaine hydrochloride, a local anesthetic used widely during dental procedures, as a potential radioprotector. Prilocaine, at a concentration of 20 µM, protected zebrafish from radiation induced (20 Gy) pericardial edema (PE), microphthalmia and rendered 60 % survival advantage over radiation exposed controls. While 40 % survival advantage over radiation exposed controls was achieved with 10 µM prilocaine. Prilocaine, in a dose-dependent manner, scavenged, radiation-induced hydroxyl radicals and maximally (43 %) at the highest concentration (1 mM) tried in this study. However, prilocaine exerted a mild superoxide anion scavenging potential (around 5 %) at all the concentrations used within this study. Prilocaine, at 20 µM concentration, significantly increased erythropoiesis, a marker for HSC function, in caudal hematopoietic tissue (CHT) in wild type and anemic zebrafish embryos (1.48 and 0.85 folds respectively) when compared to untreated (1) and phenylhydrazine (PHZ) (0.41 fold) treated control groups respectively. These results suggest that prilocaine is a radioprotective agent and free radical scavenging and HSC expanding potential seems to be contributing towards its radioprotective action.