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Hideto Jinno

Publications and source records attributed to Hideto Jinno.

26 records · Page 2Linked to original sources
PubMed2003

Glucuronidation of 7-ethyl-10-hydroxycamptothecin (SN-38), an active metabolite of irinotecan (CPT-11), by human UGT1A1 variants, G71R, P229Q, and Y486D.

7-Ethyl-10-hydroxycamptothecin (SN-38), an active metabolite of antitumor agent irinotecan (CPT-11), is conjugated and detoxified to SN-38-glucuronide by UDP-glucuronosyltransferase (UGT) 1A1. Genetic polymorphisms in UGT1A1 are thought to contribute to severe diarrhea and/or leukopenia caused by CPT-11. In this regard, it has been reported that polymorphisms in the promoter region could affect the CPT-11 pharmacokinetics and interindividual variation of toxicity. However, little information is available on the influence of UGT1A1 polymorphisms in the coding region on the SN-38 glucuronidation activity. In the present study, wild-type (WT) and three variant (G71R, P229Q, and Y486D) cDNAs of human UGT1A1s were transiently expressed in COS-1 cells, and the kinetic parameters of these UGT1A1s were determined for SN-38 glucuronidation. A partially reduced UGT1A1 protein expression was observed in COS-1 cells for G71R and Y486D. WT UGT1A1 catalyzed SN-38 glucuronidation with an apparent K(m) value of 11.5 microM, whereas those of G71R, P229Q, and Y486D were 14.0, 18.0, and 63.5 microM, respectively. The SN-38 glucuronidation efficiency ratio (V(max)/K(m)) normalized for the level of expression was 1.4, 0.66 (47% of WT), 0.73 (52%), and 0.07 (5%) microl/min/mg of protein for WT, G71R, P229Q, and Y486D, respectively. Thus, the SN-38 glucuronidation activity of Y486D was drastically reduced, whereas the reduction in the G71R and P229Q activities was fractional. The decreased SN-38 glucuronidation efficiency ratio of G71R and P229Q could be critical in combination with other polymorphisms in the UGT1A1 gene.

Amino Acid Substitution↗
PubMed2003

Functional characterization of cytochrome P450 2B6 allelic variants.

Cytochrome P450 (P450) 2B6 is a hepatic enzyme of potential importance for the metabolism of clinically used drugs and environmental or abused toxicants. Genetic polymorphisms of CYP2B6 (CYP2B6*2, CYP2B6*3, CYP2B6*4, CYP2B6*5, CYP2B6*6 and CYP2B6*7; wild-type, CYP2B6*1) were found previously in white and Japanese populations. In the present study, the goal was to investigate the effects of amino acid substitutions on CYP2B6 function. Wild-type (CYP2B6.1) and all of the known variants of CYP2B6 (CYP2B6.2, CYP2B6.3, CYP2B6.4, CYP2B6.5, CYP2B6.6, and CYP2B6.7) were transiently expressed in COS-1 cells, and their 7-ethoxy-4-trifluoromethylcoumarin O-deethylation activities were determined. The levels of the variant CYP2B6 proteins were relatively low compared with that of CYP2B6.1, although the differences were not significant. The activities of 7-ethoxy-4-trifluoromethylcoumarin O-deethylation on the basis of the CYP2B6 protein level at low (0.5 microM) and high (50 microM) substrate concentrations varied among wild-type and variant CYP2B6 proteins. All CYP2B6 enzymes showed typical Michaelis-Menten kinetics. The K(m) value of CYP2B6.6 was significantly higher than that of CYP2B6.1. Those CYP2B6 variants having a Lys262Arg substitution (CYP2B6.4, CYP2B6.6, and CYP2B6.7) showed increased values for V(max) and V(max)/K(m), whereas the kinetic parameters of CYP2B6.2 and CYP2B6.3 were not affected by the corresponding amino acid substitution. These results may mean that Lys262 in combination with other amino acid residues such as Gln172 and Arg487 is associated with the CYP2B6 function and that the genetic polymorphism of CYP2B6 leads to interindividual differences in xenobiotic metabolism.

Alleles↗
PubMed2003

Functional characterization of wild-type and variant (T202I and M59I) human UDP-glucuronosyltransferase 1A10.

UDP-glucuronosyltransferase (UGT) 1A10 is an isoform of UGT1A, which is expressed in extrahepatic, biliary and aerodigestive/gastrointestinal tissues. We have previously reported two nonsynonymous single nucleotide polymorphisms in exon 1 of human UGT1A10 gene; 177G>A and 605C>T resulting in amino acid alterations, M59I and T202I, respectively. In the present study, wild-type (WT) and these variant UGT1A10 cDNAs were transiently expressed in COS-1 cells for functional characterization. Glucuronidation activities in these COS-1 membrane fractions were assayed using 7-hydroxy-4-trifluoromethylcoumarin (HTFMC) and 17 beta-estradiol (E2) as substrates. WT and variant UGT1A10s catalyzed HTFMC glucuronidation with similar apparent K(m) values of approximately 5 microM, whereas the V(max) value of T202I normalized by the expressed UGT1A10 protein levels was nearly half of those of WT and M59I. High-performance liquid chromatography analysis of E2 glucuronide revealed that UGT1A10 catalyzed E2 3-O-glucuronidation but not 17-O-glucuronidation. Similarly, the three UGT1A10s catalyzed E2 3-O-glucuronidation with comparable apparent K(m) values (approximately 2 microM), whereas the normalized V(max) value of T202I was almost half that of WT and M59I. These results suggest that the lowered glucuronidation activity of T202I affects the gastrointestinal glucuronidation of orally administrated chemicals and the enterohepatic circulation of biliary excreted metabolites.

Animals↗
PubMed2003

Three novel single nucleotide polymorphisms in UGT1A9.

Three novel single nucleotide polymorphisms (SNPs) were found in the UDP-glucuronosyltransferase (UGT) 1A9 gene from 97 Japanese subjects (47 cancer patients and 50 cardiovascular disease patients). The detected SNPs were as follows: 1) SNP, MPJ6_U1A006; GENE NAME, UGT1A9; ACCESSION NUMBER, AF297093; LENGTH, 25 bases; 5'-AATTCTCTTAGGG/TTTCTCAGATGCC-3'. 2) SNP, MPJ6_U1A007; GENE NAME, UGT1A9; ACCESSION NUMBER, AF297093; LENGTH, 25 bases; 5'-TGTTACGGAGTAT/GGATCTCTACAGC-3'. 3) SNP, MPJ6_U1A031; GENE NAME, UGT1A9; ACCESSION NUMBER, AF297093; LENGTH, 25 bases; 5'-ACTCATTCTCAGG/AGGGCATGAGGTG-3'. All three SNPs were located in exon 1 with frequencies of 0.036 for MPJ6_U1A006, and 0.005 for MPJ6_U1A007 and MPJ6_U1A031. SNP MPJ6_U1A007 (726T>G) results in formation of a termination codon TAG (Y242X). The other two SNPs, MPJ6_U1A006 (588G>T) and MPJ6_U1A031 (153G>A), result in synonymous changes (G196G and R51R, respectively).

Journal Article↗
PubMed2002

Characterization of human CYP1A1/1A2 induction by DNA microarray and alpha-naphthoflavone.

DNA microarrays and real time PCR were used to analyze the mechanism of gene induction by CYP1A1 inducers, beta-naphthoflavone, and omeprazole, in the human hepatocellular carcinoma HepG2 cells. Reproducible and significant inductions were observed in a limited number of genes including CYP1A1 and CYP1A2. Genes induced by omeprazole included several protein tyrosine kinase targets. This result confirmed that omeprazole could modulate gene expressions through protein tyrosine kinase-mediated pathway. Induction ratios were considerably different from CYP1A1 and CYP1A2 (>10-fold) to other induced genes (<5-fold). alpha-Naphthoflavone, which is known as an antagonist to 2,3,7,8-tetrachlorodibenzo-p-dioxin, inhibited the inductions of heme oxygenase 1, glutamate-cysteine ligase (modifier unit), and thioredoxin reductase by beta-naphthoflavone but not those of CYP1A1 and CYP1A2. It unexpectedly enhanced the beta-naphthoflavone-mediated CYP1A1 and CYP1A2 induction. These results suggest that the CYP1A1 and CYP1A2 genes, which share their 5(') enhancer regions, are regulated differently from the other genes.

Antigens, Differentiation↗
PubMed2002

Interaction of irinotecan (CPT-11) and its active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38) with human cytochrome P450 enzymes.

The inhibition and mechanism-based inactivation potencies of irinotecan (7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin; CPT-11) and its active metabolite (7-ethyl-10-hydroxycamptothecin; SN-38) for human cytochrome P450 (P450) enzymes were investigated to evaluate the potential for drug interactions involving CPT-11 using microsomes from insect cells expressing specific human P450 isoforms. The mechanism and potential for interaction were examined by Lineweaver-Burk analysis, and NADPH-, time- and concentration-dependent effects were observed. CPT-11 and SN-38 competitively inhibited CYP3A4 (testosterone 6 beta-hydroxylation) activity with K(i) values of 129 and 121 microM, respectively. CYP2A6 (coumarin 7-hydroxylation) and CYP2C9 (diclofenac 4'-hydroxylation) activities exhibited a mixed type of inhibition comprising competitive and noncompetitive components in response to SN-38, the K(i) values being 181 and 156 microM, respectively. On the other hand, CYP1A2 (phenacetin O-deethylation), CYP2B6 (7-ethoxycoumarin O-deethylation), CYP2C8 (paclitaxel 6 alpha-hydroxylation), CYP2C19 (S-mephenytoin 4'-hydroxylation), CYP2D6 (bufuralol 1'-hydroxylation), and CYP2E1 (chlorzoxazone 6-hydroxylation) were hardly affected by either compound. Furthermore, CPT-11 and SN-38 were suggested to be mechanism-based inactivators of CYP3A4. The k(inact) and K(I) values of CPT-11 and SN-38 were 0.06 min(-1) and 24 microM and 0.10 min(-1) and 26 microM, respectively. However, no inactivation of CYP2A6 and CYP2C9 by SN-38 was observed. These results mean that CPT-11 and SN-38 interact with human P450 isoforms, such as CYP2A6, CYP2C9, and CYP3A4, in vitro and imply that the significant drug interactions involving CPT-11 may be caused by a mechanism-based inactivation of CYP3A4 by SN-38 as an active metabolite of CPT-11 rather than competitive inhibition.

Antineoplastic Agents, Phytogenic↗
PubMed2002

Three novel single nucleotide polymorphisms in UGT1A10.

Three novel single nucleotide polymorphisms (SNPs) were found in the UDP-glucuronosyltransferase (UGT) 1A10 gene from 24 Japanese patients with various cancers who were administered the anti-tumor drug, irinotecan (CPT-11). The detected SNPs were as follows: 1) SNP, MPJ6_U1A003; GENE NAME, UGT1A10; ACCESSION NUMBER, AF297093; LENGTH, 25 bases; 5'-CAGATGCCATGAC/TTTTCAAGGAGAG-3'. 2) SNP, MPJ6_U1A004; GENE NAME, UGT1A10; ACCESSION NUMBER, AF297093; LENGTH, 25 bases; 5'-CCTAGAAATAGCC/TTCTGAAATTCTC-3'. 3) SNP, MPJ6_U1A030; GENE NAME, UGT1A10; ACCESSION NUMBER, AF297093; LENGTH, 25 bases; 5'-GGTTGTAGTCATG/ACCAGAGGTGAGT-3' All the three SNPs were located in exon 1 and their frequencies were all 0.021. Among these SNPs, MPJ6_U1A003 and U1A030 resulted in amino acid alterations, T202I and M59I, respectively. The third SNP, MPJ6_U1A004, introduced a synonymous amino acid change (A231A).

Journal Article↗