Evaluation of Drug-metabolizing enzyme activity and-drug interaction in paitients with hepatic disease

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 12672224
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 応用薬理学・医療系薬学
• Research Institution: SHOWA UNIVERSITY
• Principal Investigator: YASUHARA Hajime Showa University school of Medicine Professor, 医学部, 教授 (70053999)
• Co-Investigator(Kenkyū-buntansha): NISHIMURA Yuki Showa University school of Medicine Research associate, 医学部, 助手 (40276572) ; KURATA Norimitsu Showa University school of Medicine Assistant Professor, 医学部, 講師 (80231299)
• Project Period (FY): 2000 – 2001
• Keywords: Human liver / Hepatic cancer / CYP2C19 / Cytochrome P-450 / microsomes / CYP / Drug metabolism

Research Abstract

Hepatic drug-metabolizing capacity mediated by cytochrome P450 is assayed in human surgical samples obtained from hepatocellular carcinoma (HCC) and metastatic cancer (MC) patients. Liver samples were donated from seven of HCC and four of MC patients. Each liver samples, apparently normal part, was used for the evaluation of drug metabolizing enzyme activity. Microsomal fraction was prepared by conventional method. Human pooled hepatic microsome from Caucasian brain death patients was employed as a reference enzyme source. Microsomal cytochrome P450 (CYP) enzyme activity, CYP1A2 (Caffeine, Ethoxyresorfin), 2C9 (Warfarin), 2C19 (Mephenytoin), 2D6 (Bufuralol), 2E1 (Chlorzoxazone) and 3A4 (Testosterone, Midazolam), were analysed by using typical substrates HPLC method was employed for the determination of each enzyme activity. CYP enzymes activity was variated from 2 to 5 fold in each CYP enzymes in both HCC and MC compared with pooled microsome CYPs activity. Furthermore, mean activity o f each CYP enzymes activity in HCC and MC liver samples compared with pooled microsomal CYP activities were quite similar in most of CYP enzymes. In CYP2C19, however, enzyme activity was quite low in both HCC and MC compared with pooled microsome. To clarify the mechanism of the expressed low activity of CYP2C19 in patient with hepatic disease, genetic profile and S-Mephenytoin 4'-hydroxylation activity in six of new patient's liver samples were analysed. Exon 4 and Exon 5 of CYP2C19 gene was analysed and all of patients has heterozygous for wild type and mutation in Exon 4 and three of 6 patients bad homozygous for mutation of Exon 5.Other 3 patients had wild type homozygous for Exon 5. Mephenytoin 4'-hydroxrylation activity was well correlated to genotype and normal level of the activity was observed in patients who has wild type homozygous in Exon 5 and quite low activity in 3 samples which has the homozygous for the mutation in Exon 5. These results in to consideration, low activity of CYP2C19 in patients with liver disease was due to the genetic deficiency of CYP2C19 gene on Exon 5.In general, 20 to 25% of again populations are genetically deficient of CYP2C19, however, in our results, quite high frequency of the enzyme deficiency was observed in patients with liver disease. These results may indicating that CYP2C19 deficiency reflect the one of the risk factor of liver disease such as hepatic cancer and/or liver cirrhosis.