Disease relevance of CYP2C9

• Phenytoin plasma concentrations and toxicity have been shown to increase in patients taking inhibitors of CYP2C19 or who have variant alleles and, because of its narrow therapeutic range, genotyping of CYP2C19 in addition to CYP2C9 may be needed to optimise the dosage of phenytoin [1].
• For women, carrying at least one variant CYP2C9 allele was inversely associated with the risk of colorectal cancer (OR=0.85, 95% CI, 0.57--1.27) when compared with *1/*1 wild-type individuals [2].
• The constructs, CYP2C9/BMR, CYP2C19/BMR and CYP3A4/BMR are well expressed in Escherichia coli as holo proteins [3].
• CYP2C9 mRNA was reduced in patients with both cholestatic and hepatocellular types of liver disease, but 2C protein was reduced only in patients with cholestatic dysfunction [4].
• Presented here are the results on the construction and characterization of three fusion proteins containing the N-terminally modified human cytochrome P450s CYP2C9, CY2C19 and CYP3A4 fused to the soluble NADPH-dependent oxidoreductase domain of CYP102A1 from Bacillus megaterium [3].
• Drugs that are metabolized by CYP2C9 increase the risk of myocardial infarction in women [5].

Psychiatry related information on CYP2C9

• Alteration of monoaminergic neurotransmission has been implicated in the pathophysiology of mood disorders, and CYP2C9 enzyme activity has been shown to be modulated by serotonin in vitro [6].
• Differences in rates of production of hydroxylamine metabolites of the drugs by cytochrome P450 (CYP2C9), myeloperoxidase, and thyroid, roxidase, along with an inherited abnormality in detoxification of the hydroxylamines are critically important in determining individual differences in adverse reaction risk [7].

High impact information on CYP2C9

• Drugs for which there is a potential case for prospective testing include warfarin (CYP2C9), perhexiline (CYP2D6), and perhaps the proton pump inhibitors (CYP2C19) [8].
• CYP2C9 is also the first human P450 to be crystallized, and the structural basis for its substrate and inhibitor selectivity is becoming increasingly clear [9].
• Clinical and toxicological relevance of CYP2C9: drug-drug interactions and pharmacogenetics [9].
• RESULTS: Among 185 patients with analyzable data, 58 (31.4%) had at least 1 variant CYP2C9 allele and 127 (68.6%) had the wild-type (*1/*1) genotype [10].
• The principal enzyme involved in warfarin metabolism is CYP2C9, and 2 relatively common variant forms with reduced activity have been identified, CYP2C9*2 and CYP2C9*3 [10].

Chemical compound and disease context of CYP2C9

• Down-regulation of astroglial CYP2C, glucocorticoid receptor and constitutive androstane receptor genes in response to cocaine in human U373 MG astrocytoma cells [11].
• The CYP2C9 genotype predicts the blood pressure response to irbesartan: results from the Swedish Irbesartan Left Ventricular Hypertrophy Investigation vs Atenolol (SILVHIA) trial [12].
• CYP3A4, CYP2C9 and CYP2B6 expression and ifosfamide turnover in breast cancer tissue microsomes [13].
• The objective of this study was to assess whether polymorphisms in UGT1A6 and CYP2C9 genes are related to the prevalence of upper gastrointestinal symptoms in cardiovascular patients using acetylsalicylic acid for secondary prevention of ischaemic heart disease [14].
• Disposition of drugs in cystic fibrosis. V. In vivo CYP2C9 activity as probed by (S)-warfarin is not enhanced in cystic fibrosis [15].

Biological context of CYP2C9

• Deletional analysis of CYP2C9 regulatory region (+21 to -2088) in the presence of various hormone nuclear receptors suggested the presence of two functional response elements, a glucocorticoid receptor-responsive element (-1648/-1684) and a constitutive androstane receptor-responsive element (CAR, -1783/-1856) [16].
• Since the order of these genes on chromosome 10q24 is CYP2C18 - CYP2C19 - CYP2C9, it is conceivable that the composite RNAs may result from multiple canonical and inverse splicing events of a long pre-mRNA that encompasses the three genes [17].
• Total serum cholesterol and low-density lipoprotein cholesterol concentrations decreased significantly during the 14-day treatment period (P <.001), but no correlation with the CYP2C9 genotype was found [18].
• Influence of CYP2C9 polymorphisms on the pharmacokinetics and cholesterol-lowering activity of (-)-3S,5R-fluvastatin and (+)-3R,5S-fluvastatin in healthy volunteers [18].
• Regulation of human CYP2C9 by the constitutive androstane receptor: discovery of a new distal binding site [19].

Anatomical context of CYP2C9

• CYP3A4, CYP2C8, and CYP2C9 protein levels were also increased by exposure of the hepatocytes to cyclophosphamide or ifosfamide (50 microM), which thereby enhanced their own rates of 4-hydroxylation in the cultured hepatocytes [20].
• We conclude that alteration of the signal transduction mediated through the GR-[CAR/PXR]-P450 cascade by colchicine is responsible for the down-regulation of CYP2C9 and CYP3A4, implicating cytoskeleton as necessary for correct functioning of this cascade under physiological conditions [21].
• Similarly, the hydroxylation of tolbutamide, a marker for CYP2C9 was undetected in fetal liver microsomes and rose in the first month after birth [22].
• Cotransfection with an HNF-4 expression plasmid increased transcriptional activity of the CYP2C9 minimal promoter (approximately 2-fold) in HepG2 cells and elevated activity more substantially in nonhepatic NIH3T3 cells (26-fold) and Cos 1 cells (9-fold).(ABSTRACT TRUNCATED AT 250 WORDS)[23]
• The Km value for 3alpha-hydroxylation by CYP2C9 cell line microsomes was 6.5 microM and the corresponding Vmax value was 1269 pmole. mg-1. min-1 [24].

Associations of CYP2C9 with chemical compounds

• Intriguingly, removal of the negative charge from either 216 or 301 produced enzymes (E216A, E216K, and D301Q) with elevated levels (50-75-fold) of catalytic activity toward diclofenac, a carboxylate-containing CYP2C9 substrate that lacks a basic nitrogen atom [25].
• In previous work, we have shown that CYP2C9 is inducible in primary human hepatocytes by xenobiotics including dexamethasone, rifampicin, and phenobarbital [16].
• Identification of these functional elements provides rational mechanistic basis for CYP2C9 induction by dexamethasone (submicromolar concentrations), and by phenobarbital and rifampicin, respectively [16].
• Data suggest that warfarin can be used as a safe and accurate biomarker for CYP2C9, and if warfarin is administered with vitamin K, the pharmacodynamic effect is ablated [26].
• The specific CYP2C9 inhibitor sulfaphenazole, on the other hand, significantly attenuated EDHF-mediated hyperpolarization and relaxation [27].

Physical interactions of CYP2C9

• Antiserum derived from the CYP2C19-immunized rabbits was reacted with CYP2C9 as well as CYP2C19 and immunoabsorbed with membrane-bound CYP2C9 expressed in E. coli [28].
• These studies strongly support the hypothesis that there is cross talk between distal CAR/PXR sites and HNF4alpha binding sites in the CYP2C9 promoter and that the HNF4alpha sites are required for maximal induction of the CYP2C9 promoter [29].

Regulatory relationships of CYP2C9

• On the other hand, cisapride strongly inhibited CYP3A4 and markedly inhibited CYP2C9 [30].
• Sulfaphenazole, flavoxamine, and antibodies raised against purified liver cytochrome P450 (P450) 2C9 that inhibit both CYP2C9- and 2C19-dependent activities, significantly inhibited microsomal oxidations of (+)- and (-)-limonene enantiomers [31].
• Overexpression of CYP2C9 and stimulation with 11,12-EET increased intracellular cAMP levels and stimulated DNA-binding of the cAMP-response element-binding protein [32].
• Both CAR and PXR transcriptionally up-regulate the CYP2C9 promoter via these elements [29].

Other interactions of CYP2C9

• Whereas CYP2C8 and CYP2C9 have the characteristics of low Km oxazaphosphorine 4-hydroxylases, CYP2A6, -2B6, and -3A4 are high Km forms [33].
• Expression of CYP3A4, CYP2B6, and CYP2C9 is regulated by the vitamin D receptor pathway in primary human hepatocytes [34].
• Western blotting confirmed abundant expression of these CYP4 proteins in human kidney and revealed that other AA-oxidizing P450s, including CYP2C8, CYP2C9, and CYP2E1, were not expressed [35].
• Transcriptional regulation of CYP2C9 gene. Role of glucocorticoid receptor and constitutive androstane receptor [16].
• Phenotypic measurements were in concordance with the subject's CYP2C9, CYP2C19, and CYP2D6 genotypes [26].

Analytical, diagnostic and therapeutic context of CYP2C9

• Rapid amplification of cDNA ends (RACE) and PCR amplifications of human liver cDNA revealed the presence of several intergenic species containing the CYP2C18 exon 1-like sequence spliced to different combinations of exonic and intronic sequences from the CYP2C9 gene [36].
• Chromatin immunoprecipitation assay demonstrated in vivo binding of HNF4alpha and PGC1alpha to HNF4alpha response sequences in the CYP2C9 promoter and to three new regulatory regions in the common 23.3 kilobase spacer sequence of the CYP1A1/2 cluster [37].
• Immunoblotting analysis of human liver microsomes suggested that CYP2C9 is a major component of the human CYP2C enzyme pool; it accounted for approximately 20% of total P450 in liver microsomes of both human populations [38].
• Gel shift analysis demonstrated that nuclear proteins from HepG2 cells had a high binding affinity for a 20-bp oligonucleotide containing the HPF-1 site of CYP2C9 [23].
• Multiple sequence alignment of CYPs identified CYP2C9 Asp(293) as corresponding to Asp(301) of CYP2D6, which has been suggested to play a role in the binding of basic substrates to the latter enzyme [39].

References