The Center for Alternatives to Animal Testing is an academic center affiliated with the Division of Toxicological Sciences in the Department of Environmental Health Sciences of the Johns Hopkins University Bloomberg School of Public Health.

 

Johns Hopkins School of Public Health

Research Grants 2001-2002

Evaluation of CYP3A Induction with Engineered Cell Lines

Bingfang Yan, DVM, PhD
University of Rhode Island, Kingston, Rhode Island

Cytochrome P450 (CYP) enzymes are a family of heme-containing proteins and rank first among the phase I biotransformation enzymes in terms of catalytic versatility and the number of xenobiotics they metabolize. Cytochrome P4503A (CYP3A) enzymes are the most abundant P450 enzymes and involve the metabolism of two thirds of xenobiotics. Numerous drugs and other envirnomental chemicals are known to increase the expression of CYP3A enzymes (induction), thus cause drug-drug interactions. The Food and Drug Administration request all new drugs be tested for CYP induction. Screening of CYP3A induction, however, has been exclusively dependent upon the use of human hepatocytes and animals. The availability of human livers, the use of a large number of animals and potential species difference are the primary limited factors in rapidly predicting the effects of drugs or other chemicals on CYP3A induction. Studies on molecular signaling have revealed that induction of CYP3A enzymes is largely due to transcription activation mediated by the pregnane X receptor (PXR). The proposed studies are designed to develop and validate a PXR-based in vitro system for screening CYP3A induction. The ultimate goal of the proposed studies is to establish stably transfected cells that can be used for screening CYP3A inducers, The transfected cells will express high and stable levels of PXR, and have a reporter gene integrated into the genome. The reporter encodes a luciferase and is subjected to the PXR-mediated regulation upon binding to a CYP3A inducer. Therefore, this system will provide a screening procedure featured by simplicity, high sensitivity and unlimited supplies.