ABSTRACT
INTRODUCTION: To evaluate the usefulness of in silico assay in predicting drug-induced QTc prolongation and ventricular proarrhythmia, we describe in this study 2-dimensional transmural ventricular wedge preparation model (2D model) of non-failing (non-FH) and failing hearts (FH) based on O'Hara-Rudy dynamic model of human ventricular myocytes. METHODS: Using the prepared 2D model, we simulated ventricular action potential and recorded electrocardiogram for the non-FH and FH. The FH model was constructed based on differences in mRNA, protein, and/or current levels of ion channels between non-diseased heart and failing heart. To simulate the effects of selected drugs, we incorporated changes in ion channel conductance depending on the IC50 value and Hill coefficient at unbound drug blood concentrations. RESULTS: Dofetilide concentration-dependently induced QTc prolongation at therapeutic concentration in the 2D model of both non-FH and FH. The QTc prolongation in FH was longer than that in non-FH. These findings are consistent with previously reported clinical data. At supratherapeutic concentration 20nM, dofetilide induced Torsade de Pointes-like arrhythmia in the 2D non-FH model. In contrast, the single ventricular myocyte model did not quantitatively reproduce experimental data due to lack of electrotonic interaction. The simulated QTc change induced by six drugs examined in the IQ-CSRC prospective study was almost equivalent to that recorded in drug-treated healthy volunteers. DISCUSSION: Our 2D model with or without heart failure faithfully reproduced drug-induced QT prolongation and ventricular arrhythmias, suggesting that the in silico approach is a powerful tool for predicting cardiac safety of drug candidates at preclinical stage.
Subject(s)
Action Potentials/drug effects , Drugs, Investigational/adverse effects , Heart Failure/chemically induced , Heart Ventricles/drug effects , Models, Cardiovascular , Myocytes, Cardiac/drug effects , Computer Simulation , Electrocardiography , Heart Failure/physiopathology , Heart Ventricles/physiopathology , Humans , Long QT Syndrome/chemically induced , Long QT Syndrome/physiopathology , Myocytes, Cardiac/physiologyABSTRACT
The human ether-a-go-go-related gene (HERG) potassium current (IHERG) has been shown to decrease in amplitude following stimulation with Gq protein-coupled receptors (GqRs), such as α1-adrenergic and M1-muscarinic receptors (α1R and M1R, respectively), at least partly via the reduction of membrane phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). The present study was designed to investigate the modulation of HERG channels by PI(4,5)P2 and phosphatidylinositol4-phosphate 5-kinase (PI(4)P5-K), a synthetic enzyme of PI(4,5)P2. Whole-cell patch-clamp recordings were used to examine the activity of HERG channels expressed heterologously in Chinese Hamster Ovary cells. The stimulation of α1R with phenylephrine or M1R with acetylcholine decreased the amplitude of IHERG accompanied by a significant acceleration of deactivation kinetics and the effects on IHERG were significantly attenuated in cells expressing PI(4)P5-K. The density of IHERG in cells expressing GqRs alone was significantly increased by the coexpression of PI(4)P5-K without significant differences in the voltage dependence of activation and deactivation kinetics. The kinase-deficient substitution mutant, PI(4)P5-K-K138A did not have these counteracting effects on the change in IHERG by M1R stimulation. These results suggest that the current density of IHERG is closely dependent on the membrane PI(4,5)P2 level, which is regulated by PI(4)P5-K and GqRs and that replenishing PI(4,5)P2 by PI(4)P5-K recovers IHERG.
Subject(s)
Ether-A-Go-Go Potassium Channels/drug effects , Phosphotransferases (Alcohol Group Acceptor)/physiology , Acetylcholine/pharmacology , Animals , CHO Cells , Cricetinae , Cricetulus , Ether-A-Go-Go Potassium Channels/physiology , GTP-Binding Protein alpha Subunits, Gq-G11/drug effects , Humans , Membrane Potentials/drug effects , Membrane Potentials/physiology , Mutation , Phenylephrine/pharmacology , Phosphatidylinositol 4,5-Diphosphate/physiology , Phosphotransferases (Alcohol Group Acceptor)/genetics , TransfectionABSTRACT
A series of peptide-based transition-state human neutrophil elastase (HNE) inhibitors with N-terminal acidic moieties were synthesized and their inhibitory activity against HNE was evaluated both in vitro and in vivo. Our results show that compounds containing cyclic amide bridged acidic moieties at the N-terminal have not only improved water solubility but also high in vivo potency. Among these compounds, AE-3763 showed remarkable efficacy in hamster models of elastase-induced lung hemorrhage and lipopolysaccharide (LPS)-induced lung injury as well as in a mouse model of LPS/galactosamine-induced acute multiple organ dysfunctions. The water solubility of AE-3763 (>1000 mg/ml in H(2)O) was also far superior to that of any of the other compounds synthesized. Thus, it is believed that AE-3763 would be useful for treatment of HNE-associated respiratory disorders, such as acute respiratory distress syndrome (ARDS), acute lung injury (ALI), and acute exacerbation of chronic obstructive pulmonary disease (COPD).
Subject(s)
Acute Lung Injury/drug therapy , Dipeptides/chemistry , Leukocyte Elastase/antagonists & inhibitors , Peptides/chemistry , Proteinase Inhibitory Proteins, Secretory/chemistry , Animals , Cricetinae , Dipeptides/chemical synthesis , Dipeptides/pharmacology , Disease Models, Animal , Galactosamine/toxicity , Humans , Leukocyte Elastase/metabolism , Lipopolysaccharides/toxicity , Mice , Proteinase Inhibitory Proteins, Secretory/chemical synthesis , Proteinase Inhibitory Proteins, Secretory/pharmacology , SolubilityABSTRACT
We have previously reported that (4R,5R)-5-ethyl-2-imino-4-methylthiazolidine (3) strongly inhibits inducible nitric oxide synthase (iNOS). In a successive search for strong and selective iNOS inhibitors, we, herein, describe the synthesis of the selenium analogue of 3 (4: ES-2133) and its related optically active compounds and examine their in vitro and in vivo inhibitory activity against iNOS. In addition, an alternative synthetic method to the selected compound 4 and its pharmacokinetic profile is also reported.
Subject(s)
Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacokinetics , Nitric Oxide Synthase/antagonists & inhibitors , Organoselenium Compounds/chemical synthesis , Organoselenium Compounds/pharmacokinetics , Arginine/antagonists & inhibitors , Biological Availability , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical , Enzyme Inhibitors/chemistry , Kinetics , Molecular Conformation , Nitric Oxide Synthase Type II , Organoselenium Compounds/chemistry , Selenium/chemistry , Structure-Activity RelationshipABSTRACT
In the course of our search for selective iNOS inhibitors, we have previously reported that 2-imino-1,3-oxazolidine derivatives (1) and 2-aminothiazole derivatives (2) are selective iNOS inhibitors. In order to find more potent iNOS inhibitors, we focused our efforts on the synthesis and evaluation of the inhibitory activity against iNOS and selectivity for iNOS both in vitro and in vivo of a series of 2-imino-1,3-thiazolidine derivatives (3), which are analogues of 1 and 2. Our results show that among the compounds synthesized (4R,5R)-5-ethyl-2-imino-4-methyl-1,3-thiazolidine [(4R,5R)-14a: ES-1537] exhibited potent inhibitory activity and selectivity for iNOS. In addition, ES-1537 had good pharmacokinetic profile in rats with BA value of 80%. It is therefore expected that ES-1537 may be therapeutically useful for the treatment of diseases related to excess production of NO.
