A novel assessment of nefazodone-induced hERG inhibition by electrophysiological and stereochemical method.

Nefazodone was used widely as an antidepressant until it was withdrawn from the U.S. market in 2004 due to hepatotoxicity. We have investigated methods to predict various toxic effects of drug candidates to reduce the failure rate of drug discovery. An electrophysiological method was used to assess the cardiotoxicity of drug candidates. Small molecules, including withdrawn drugs, were evaluated using a patch-clamp method to establish a database of hERG inhibition. Nefazodone inhibited hERG channel activity in our system. However, nefazodone-induced hERG inhibition indicated only a theoretical risk of cardiotoxicity. Nefazodone inhibited the hERG channel in a concentration-dependent manner with an IC50 of 45.3nM in HEK-293 cells. Nefazodone accelerated both the recovery from inactivation and its onset. Nefazodone also accelerated steady-state inactivation, although it did not modify the voltage-dependent character. Alanine mutants of hERG S6 and pore region residues were used to identify the nefazodone-binding site on hERG. The hERG S6 point mutants Y652A and F656A largely abolished the inhibition by nefazodone. The pore region mutant S624A mildly reduced the inhibition by nefazodone but T623A had little effect. A docking study showed that the aromatic rings of nefazodone interact with Y652 and F656 via π-π interactions, while an amine interacted with the S624 residue in the pore region. In conclusion, Y652 and F656 in the S6 domain play critical roles in nefazodone binding.

The Usefulness of Three-dimensional Computed Tomography as an Assessment of Periacetabular Osteolysis in Revision Total Hip Arthroplasty.

PURPOSE: This study was performed to determine the usefulness of three-dimensional computed tomography (3D-CT) in measuring periacetabular osteolysis by comparing the real volume of osteolysis in revision surgery. MATERIALS AND METHODS: Twnety-three patients who had undergone revision surgery due to periacetabular osteolysis but not included septic osteolysis and implant loosening. The mean age of patients at the time of surgery was 55.2 years. And the mean time interval between the primary total hip arthroplasty and revision surgery was 13.3 years. We measured the polyethylene wear in plain radiographs using computer assisted vector wear analysis program, the volume of acetabular osteolytic lesions in high-resolution spiral CT scans using Rapidia 3D software version 2.8 algorithms before the revision surgery were performed. Intraoperative real osteolytic volume was calculated as the sum of the volumetric increments of the acetabular cup and impacted allo-cancellous bone volume. RESULTS: Strong correlation was found between the volume of acetabular osteolytic lesions measured on 3D-CT and intraoperative real osteolytic volume which was calculated as the sum of the volumetric increments of the acetabular cup and impacted allo-cancellous bone volume. CONCLUSION: 3D-CT is considered a useful method for assessing and measuring the volume of periacetabular osteolysis before revision surgery.

Determination of mesoridazine by liquid chromatography-tandem mass spectrometry and its application to pharmacokinetic study in rats.

The object of the present study was to develop and validate an assay method of mesoridazine in rat plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Plasma samples from rats were prepared by simple protein precipitation and injected onto the LC-MS/MS system for quantification. Mesoridazine and chlorpromazine as an internal standard (IS) were separated by a reversed phase C18 column. A mobile phase was composed of 10mM ammonium formate in water and acetonitrile (ACN) (v/v) by a linear gradient system, increasing the percentage of ACN from 2% at 0.4min to 98% at 2.5min with 4min total run time. The ion transitions monitored in positive-ion mode [M+H](+) of multiple-reaction monitoring (MRM) were m/z 387>126 for mesoridazine and m/z 319>86 for IS. The detector response was specific and linear for mesoridazine at concentrations within the range 0.001-4µg/ml and the correlation coefficient (R(2)) was greater than 0.999 and the signal-to-noise ratios for the samples were ≥10. The intra- and inter-day precision and accuracy of the method were determined to be within the acceptance criteria for assay validation guidelines. The matrix effects were approximately 101 and 99.5% from rat plasma for mesoridazine and chlorpromazine, respectively. Mesoridazine was stable under various processing and/or handling conditions. Mesoridazine concentrations were readily measured in rat plasma samples after intravenous and oral administration. This assay method can be practically useful to the pharmacokinetic and/or toxicokinetic studies of mesoridazine.

Predicted drug-induced bradycardia related cardio toxicity using a zebrafish in vivo model is highly correlated with results from in vitro tests.

Several in vivo and in vitro studies have assessed methods of evaluating the cardio toxicity of compounds during drug development due to its importance for predicting human toxicity. However, in vivo/in vitro relationships have not yet been reported using a zebrafish model. This study determined the bradycardia of 15 compounds by evaluating the change in heart beat rate (HBR) in zebrafish, hERG fluorescence polarization (hERG-FP), and ionic current change using a patch clamp (hERG-PC). In addition, a model for prediction of drug-induced bradycardia was established using in vivo and in vitro assays designed for high-throughput toxicological screening. The IC(50) values correlated well in two in vitro studies (R(2)=0.9). The change in HBR in zebrafish caused by the compounds could be estimated using the IC(50) from the hERG-FP assay [(i.e., % of HBR=19.5×log(IC(50), hERG-FP)] or hERG-PC assay [(i.e., % of HBR=19.6×log(IC(50), hERG-FP)]. To validate the predictive model, 10 unknown compounds were used and the percentages of the HBR were estimated using the model. The observed and predicted HBR% for the compounds in zebrafish were well-correlated (R(2)=0.948). Therefore, the proposed models were useful for prediction of drug-induced bradycardia related cardio toxicity.

Synthesis of LipidGreen2 and its application in lipid and fatty liver imaging.

We have developed LipidGreen2, a second generation small molecule probe for lipid imaging. LipidGreen2 has a better fluorescence signal compared with the previous LipidGreen, and selectively stains neutral lipids in cells and fat deposits in live zebrafish. We also demonstrate the application of LipidGreen2 for detecting fatty liver.