Using chimeric mice with humanized livers to predict human drug metabolism and a drug-drug interaction.

Interspecies differences in drug metabolism have made it difficult to use preclinical animal testing data to predict the drug metabolites or potential drug-drug interactions (DDIs) that will occur in humans. Although chimeric mice with humanized livers can produce known human metabolites for test substrates, we do not know whether chimeric mice can be used to prospectively predict human drug metabolism or a possible DDI. Therefore, we investigated whether they could provide a more predictive assessment for clemizole, a drug in clinical development for the treatment of hepatitis C virus (HCV) infection. Our results demonstrate, for the first time, that analyses performed in chimeric mice can correctly identify the predominant human drug metabolite before human testing. The differences in the rodent and human pathways for clemizole metabolism were of importance, because the predominant human metabolite was found to have synergistic anti-HCV activity. Moreover, studies in chimeric mice also correctly predicted that a DDI would occur in humans when clemizole was coadministered with a CYP3A4 inhibitor. These results demonstrate that using chimeric mice can improve the quality of preclinical drug assessment.

Pathomechanism of entrapment neuropathy in diabetic and nondiabetic rats reared in wire cages.

To examine the pathomechanism of entrapment neuropathy associated with diabetes with special emphasis on the roles of mast cells and Tenascin-C using a rat model of Streptozotocin-induced diabetes. The roles of mast cells and Tenascin-C in development of tarsal tunnel syndrome were analyzed electrophysiologically and histologically in 20 male Ws/Ws-/-rats (mast cell deficient) and 20 of their male wild type counterparts (12-16 weeks old; 250-300 g). Rats were assigned randomly to one of the following three groups; diabetic group and nondiabetic group reared in cages with a wire grid flooring; non-diabetic group in cages with sawdust covered plastic flooring. No significant role for mast cells in entrapment neuropathy was found in the rats with streptozotocin-induced diabetes. Distal latency was prolonged in diabetic rats compared with nondiabetic rats, and positively correlated with increases in blood glucose levels. Tenascin-C expression levels in the endoneurium at the tarsal tunnel in diabetic rats were found to be correlated with distal latency. The anti-alpha-smooth muscle actin (alpha-SMA) positive myofibroblast was scattered in nerve fascicles overexpressing Tenascin-C. It seems likely that Tenascin-C expressing myofibroblasts constrict axons by inducing collagen contraction of the endoneurium. Our data indicate that metabolic and phenotypic abnormalities of endoneurium and perineum lie behind the vulnerability of diabetic patients to entrapment neuropathy.