Metabolic Disposition of Triazolam and Clobazam in Humanized CYP3A Mice with a Double-Knockout Background of Mouse Cyp2c and Cyp3a Genes

Contribution of Japanese scientists to drug metabolism and disposition

Japanese researchers have played a pivotal role in advancing the field of drug metabolism and disposition, as demonstrated by their substantial contributions to the journal Drug Metabolism and Disposition (DMD) over the past 5 decades. This review highlights the historical and ongoing impact of Japanese scientists on DMD, celebrating their achievements in elucidating drug metabolism, membrane transport, pharmacokinetics, and toxicology. From the discovery of cytochrome P450 by Tsuneo Omura and Ryo Sato in 1962 to subsequent advances in drug transport research, Japan has maintained a leading position in the field. A geographical analysis of DMD publications reveals a notable increase in contributions from Japan during the 1980s, ranking second globally and maintaining this position through the 2000s. However, recent years have seen a slight decline in output, likely influenced by the COVID-19 pandemic and increased online journals as well as structural changes within academia and industry. Importantly, this trend is not unique to Japan. To sustain excellence and innovation in this field, it is crucial to strengthen funding for absorption, distribution, metabolism, excretion, and toxicity research and promote collaborations between academia, industry, and regulatory agencies. By prioritizing the translation of fundamental discoveries into drug development and clinical applications, scientists in this area can further advance global efforts toward achieving optimal drug efficacy and safety. This review underscores the enduring contributions of Japanese researchers to DMD and calls for renewed efforts to drive innovation and progress in this vital area of science. SIGNIFICANCE STATEMENT: Over the past 5 decades, Japanese scientists have made significant contributions to Drug Metabolism and Disposition through groundbreaking discoveries and advancements in the study of drug-metabolizing enzymes, transporters, pharmacokinetics analysis, and related areas. These contributions continue to shape the field, offering a foundation for future innovation in this area. We hope that the next generation of Japanese scientists will further solidify their global leadership in this area to advance drug development and proper pharmacotherapy.

Induction of hepatic CYP3A4 expression by cholesterol and cholic acid: Alterations of gene expression, microsomal activity, and pharmacokinetics

Human cytochrome P450 3A4 (CYP3A4) is a drug-metabolizing enzyme that is abundantly expressed in the liver and intestine. It is an important issue whether compounds of interest affect the expression of CYP3A4 because more than 30% of commercially available drugs are metabolized by CYP3A4. In this study, we examined the effects of cholesterol and cholic acid on the expression level and activity of CYP3A4 in hCYP3A mice that have a human CYP3A gene cluster and show human-like regulation of the coding genes. A normal diet (ND, CE-2), CE-2 with 1% cholesterol and 0.5% cholic acid (HCD) or CE-2 with 0.5% cholic acid was given to the mice. The plasma concentrations of cholesterol, cholic acid and its metabolites in HCD mice were higher than those in ND mice. In this condition, the expression levels of hepatic CYP3A4 and the hydroxylation activities of triazolam, a typical CYP3A4 substrate, in liver microsomes of HCD mice were higher than those in liver microsomes of ND mice. Furthermore, plasma concentrations of triazolam in HCD mice were lower than those in ND mice. In conclusion, our study suggested that hepatic CYP3A4 expression and activity are influenced by the combination of cholesterol and cholic acid in vivo.