1.In vitro functional analysis of 24 novel CYP2C19 variants recently found in the Chinese Han population.
Dai DP1, Hu LM2, Geng PW3, Wang SH3, Cai J1,4, Hu GX4, Cai JP1. Xenobiotica. 2015;45(11):1030-5. doi: 10.3109/00498254.2015.1028512. Epub 2015 Jul 7.
1. CYP2C19 is a highly polymorphic enzyme responsible for the metabolism of a wide range of clinical drugs. Alterations to the CYP2C19 gene contribute to the variability of CYP2C19 enzyme activity, which causes pharmacokinetics and drug efficacies to vary and adverse drug reactions to occur in different persons. Recently, we identified 24 novel CYP2C19 allelic variants in the Chinese Han population. The purpose of present study is to assess the impact of these newly found nucleotide mutations on the enzymatic activity of the CYP2C19 protein. 2. Dual-expression vectors were constructed and transiently transfected into 293FT cells. Forty-eight hours after transfection, cells were re-suspended and incubated with two typical probe substrates, omeprazole and S-mephenytoin, to determine the activities of each variant relative to the wild-type protein. 3. Immunoblotting results showed that the protein expression levels of the CYP2C19 variants were diverse.
2.Sodium tanshinone IIA sulfonate and its interactions with human CYP450s.
Chen D1, Lin XX1, Huang WH1, Zhang W1, Tan ZR1, Peng JB1, Wang YC2, Guo Y2, Hu DL2, Chen Y1,2. Xenobiotica. 2016 Mar 2:1-8. [Epub ahead of print]
1.Sodium tanshinone IIA sulfonate (STS) is a water-soluble derivative of tanshinone IIA, a famous Chinese medicine used for many years to treat cardiovascular disorders. However, the role of cytochrome P450 (CYP) enzymes in the metabolism of STS was unclear. In this study, we screened the main CYPs for the metabolism of STS and studied their interactions in vitro. 2.Seven CYPs were screened for the metabolism of STS by human liver microsomes (HLMs) or recombinant CYP isoforms. To determine the potential of STS to affect CYP-mediated phase I metabolism in humans, phenacetin (CYP1A2), coumarin (CYP2A6), tolbutamide (CYP2C9), metoprolol (CYP2D6), chlorzoxazone (CYP2E1), S-Mephenytoin (CYP2C19), and midazolam (CYP3A4) were used as the respective probe substrates. Enzyme kinetic studies were performed to investigate the mode of inhibition of the enzyme-substrate interactions. 3.STS inhibited the activity of CYP3A4 in a dose-dependent manner in the HLMs and CYP3A4 isoform.
3.Metabolism of (-)-cis- and (-)-trans-rose oxide by cytochrome P450 enzymes in human liver microsomes.
Nakahashi H1, Yamamura Y1, Usami A1, Rangsunvigit P2, Malakul P2, Miyazawa M1. Biopharm Drug Dispos. 2015 Dec;36(9):565-74. doi: 10.1002/bdd.1965. Epub 2015 Oct 31.
The in vitro metabolism of (-)-cis- and (-)-trans-rose oxide was investigated using human liver microsomes and recombinant cytochrome P450 (P450 or CYP) enzymes for the first time. Both isomers of rose oxide were incubated with human liver microsomes, and the formation of the respective 9-oxidized metabolite were determined using gas chromatography-mass spectrometry (GC-MS). Of 11 different recombinant human P450 enzymes used, CYP2B6 and CYP2C19 were the primary enzymes catalysing the metabolism of (-)-cis- and (-)-trans-rose oxide. CYP1A2 also efficiently oxidized (-)-cis-rose oxide at the 9-position but not (-)-trans-rose oxide. α-Naphthoflavone (a selective CYP1A2 inhibitor), thioTEPA (a CYP2B6 inhibitor) and anti-CYP2B6 antibody inhibited (-)-cis-rose oxide 9-hydroxylation catalysed by human liver microsomes. On the other hand, the metabolism of (-)-trans-rose oxide was suppressed by thioTEPA and anti-CYP2B6 at a significant level in human liver microsomes.
4.The CYP2C19 Intron 2 Branch Point SNP is the Ancestral Polymorphism Contributing to the Poor Metabolizer Phenotype in Livers with CYP2C19*35 and CYP2C19*2 Alleles.
Chaudhry AS1, Prasad B1, Shirasaka Y1, Fohner A1, Finkelstein D1, Fan Y1, Wang S1, Wu G1, Aklillu E1, Sim SC1, Thummel KE1, Schuetz EG2. Drug Metab Dispos. 2015 Aug;43(8):1226-35. doi: 10.1124/dmd.115.064428. Epub 2015 May 28.
CYP2C19 rs12769205 alters an intron 2 branch point adenine leading to an alternative mRNA in human liver with complete inclusion of intron 2 (exon 2B). rs12769205 changes the mRNA reading frame, introduces 87 amino acids, and leads to a premature stop codon. The 1000 Genomes project (http://browser.1000genomes.org/index.html) indicated rs12769205 is in linkage disequilibrium with rs4244285 on CYP2C19*2, but found alone on CYP2C19*35 in Blacks. Minigenes containing rs12769205 transfected into HepG2 cells demonstrated this single nucleotide polymorphism (SNP) alone leads to exon 2B and decreases CYP2C19 canonical mRNA. A residual amount of CYP2C19 protein was detectable by quantitative proteomics with tandem mass spectrometry in CYP2C19*2/*2 and *1/*35 liver microsomes with an exon 2 probe. However, an exon 4 probe, downstream from rs12769205, but upstream of rs4244285, failed to detect CYP2C19 protein in livers homozygous for rs12769205, demonstrating rs12769205 alone can lead to complete loss of CYP2C19 protein.