Hepatocellular toxicity and pharmacological effect of amiodarone and amiodarone derivatives.

The aim of this work was to compare hepatocellular toxicity and pharmacological activity of amiodarone (2-n-butyl-3-[3,5 diiodo-4-diethylaminoethoxybenzoyl]-benzofuran; B2-O-Et-N-diethyl) and of eight amiodarone derivatives. Three amiodarone metabolites were studied, namely, mono-N-desethylamiodarone (B2-O-Et-NH-ethyl), di-N-desethylamiodarone (B2-O-Et-NH(2)), and (2-butyl-benzofuran-3-yl)-(4-hydroxy-3,5-diiodophenyl)-methanone (B2) carrying an ethanol side chain [(2-butylbenzofuran-3-yl)-[4-(2-hydroxyethoxy)-3,5-diiodophenyl]-methanone; B2-O-Et-OH]. In addition, five amiodarone analogs were investigated, namely, N-dimethylamiodarone (B2-O-Et-N-dimethyl), N-dipropylamiodarone (B2-O-Et-N-dipropyl), B2-O-carrying an acetate side chain [[4-(2-butyl-benzofuran-3-carbonyl)-2,6-diiodophenyl]-acetic acid; B2-O-acetate], B2-O-Et carrying an propionamide side chain (B2-O-Et-propionamide), and B2-O carrying an ethyl side chain [(2-butylbenzofuran-3-yl)-(4-ethoxy-3,5-diiodophenyl)-methanone; B2-O-Et]. A concentration-dependent increase in lactate dehydrogenase leakage from HepG2 cells and isolated rat hepatocytes was observed in the presence of amiodarone and of most analogs, confirming their hepatocellular toxicity. Using freshly isolated rat liver mitochondria, amiodarone and most analogs showed a dose-dependent toxicity on the respiratory chain and on beta-oxidation, significantly reducing the respiratory control ratio and oxidation of palmitate, respectively. The reactive oxygen species concentration in hepatocytes increased time-dependently, and apoptotic/necrotic cell populations were identified using flow cytometry and annexin V/propidium iodide staining. The effect of the three least toxic amiodarone analogs on the human ether-a-go-go-related gene (hERG) channel was compared with amiodarone. Amiodarone, B2-O-acetate, and B2-O-Et-N-dipropyl (each 10 microM) significantly reduced the hERG tail current amplitude, whereas 10 microM B2-O-Et displayed no detectable effect on hERG outward potassium currents. In conclusion, three amiodarone analogs (B2-O-Et-N-dipropyl, B2-O-acetate, and B2-O-Et) showed a lower hepatocellular toxicity profile than amiodarone, and two of these analogs (B2-O-Et-N-dipropyl and B2-O-acetate) retained hERG channel interaction capacity, suggesting that amiodarone analogs with class III antiarrhythmic activity and lower hepatic toxicity could be developed.

Green tea extract and its major polyphenol (-)-epigallocatechin gallate improve muscle function in a mouse model for Duchenne muscular dystrophy.

Duchenne muscular dystrophy is a frequent muscular disorder caused by mutations in the gene encoding dystrophin, a cytoskeletal protein that contributes to the stabilization of muscle fiber membrane during muscle activity. Affected individuals show progressive muscle wasting that generally causes death by age 30. In this study, the dystrophic mdx(5Cv) mouse model was used to investigate the effects of green tea extract, its major component (-)-epigallocatechin gallate, and pentoxifylline on dystrophic muscle quality and function. Three-week-old mdx(5Cv) mice were fed for either 1 or 5 wk a control chow or a chow containing the test substances. Histological examination showed a delay in necrosis of the extensor digitorum longus muscle in treated mice. Mechanical properties of triceps surae muscles were recorded while the mice were under deep anesthesia. Phasic and tetanic tensions of treated mice were increased, reaching values close to those of normal mice. The phasic-to-tetanic tension ratio was corrected. Finally, muscles from treated mice exhibited 30-50% more residual force in a fatigue assay. These results demonstrate that diet supplementation of dystrophic mdx(5Cv) mice with green tea extract or (-)-epigallocatechin gallate protected muscle against the first massive wave of necrosis and stimulated muscle adaptation toward a stronger and more resistant phenotype.