No abstract

Drug-induced liver injury is a major cause of safety-related drug-marketing withdrawals. Several drugs have been reported to disrupt mitochondrial function, resulting in hepatotoxicity. The development of a simple and effective in vitro assay to identify the potential for mitochondrial toxicity is thus desired to minimize the risk of causing hepatotoxicity and subsequent drug withdrawal. An in vitro test method called the "glucose-galactose" assay is often used in drug development but requires prior-culture of cells over several passages for mitochondrial adaptation, thereby restricting use of the assay. Here, we report a rapid version of this method with the same predictability as the original method. We found that replacing the glucose in the medium with galactose resulted in HepG2 cells immediately shifting their energy metabolism from glycolysis to oxidative phosphorylation due to drastic energy starvation; in addition, the intracellular concentration of ATP was reduced by mitotoxicants when glucose in the medium was replaced with galactose. Using our proposed rapid method, mitochondrial dysfunction in HepG2 cells can be evaluated by drug exposure for one hour without a pre-culture step. This rapid assay for mitochondrial toxicity may be more suitable for high-throughput screening than the original method at an early stage of drug development.

1. In order to evaluate the inhibition activity of 1-aminobenzotriazole (ABT) and (-)-borneol (borneol) against cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT), the substrates of these metabolic enzymes were incubated with ABT and borneol in human hepatocytes. We found that 3 mM ABT and 300 μM borneol were the most suitable experimental levels to specifically inhibit CYP and UGT. 2. Montelukast, mefenamic acid, flufenamic acid, diclofenac, tienilic acid, gemfibrozil, ibufenac and repaglinide were markedly metabolized in human hepatocytes, and the metabolism of gemfibrozil, mefenamic acid and flufenamic acid was inhibited by borneol. With regard to repaglinide, montelukast, diclofenac and tienilic acid, metabolism was inhibited by ABT. Ibufenac was partly inhibited by both inhibitors. Zomepirac, tolmetin, ibuprofen, indomethacin and levofloxacin were moderately metabolized by human hepatocytes, and the metabolism of zomepirac, ibuprofen and indomethacin was equally inhibited by both ABT and borneol. The metabolism of tolmetin was strongly inhibited by ABT, and was also inhibited weakly by borneol. Residual drugs, telmisartan, valsartan, furosemide, naproxen and probenecid were scarcely metabolized. 3. Although we attempted to predict the toxicological risks of drugs containing carboxylic groups from the combination chemical stability and CLint via UGT, the results indicated that this combination was not sufficient and that clinical daily dose is important.

Change in small intestinal brush border membranes of rats following methotrexate administration was monitored by the fluorescence spectra and polarization of the cationic fluorescent probe, safranin 0. Total protein content of brush border membranes of treated rats was less than that of control rats, whereas no significant difference in total sialic acid content of brush border membranes was observed between them. Thus, an apparent increase in the electronegative charge of brush border membrane vesicles per unit of membrane protein following methotrexate administration may possibly cause the change in fluorescence spectra and polarization of safranin 0.

Teriparatide is a potent therapeutic agent for the treatment of osteoporosis. One of the aims of this analysis was to develop a population pharmacokinetic (PPK) model to understand the pharmacokinetic characteristics of the once-weekly formulation of teriparatide. Another aim was to develop an exposure-response model to describe the relationship between change in bone mineral density (BMD) and teriparatide exposure after weekly subcutaneous administration. The PPK analysis showed that apparent total body clearance was significantly influenced by estimated creatinine clearance and the presence of osteoporosis. A data set consisting of lumbar spine BMD values for 513 osteoporosis patients whose area under the concentration-time curve (AUC) of teriparatide acetate was estimated by the developed PPK model was then compiled. Exposure-response analysis showed that the percentage change from baseline of BMD was well described by a function of the AUC of teriparatide acetate, time, and coadministration of alfacalcidol and a calcium preparation. The analysis indicated that AUC is an important parameter for predicting BMD response to once-weekly teriparatide in osteoporosis patients.