Pharmacogenetics of drug-metabolizing enzymes: implications for a safer and more effective drug therapy.

The majority of phase I- and phase II-dependent drug metabolism is carried out by polymorphic enzymes which can cause abolished, quantitatively or qualitatively decreased or enhanced drug metabolism. Several examples exist where subjects carrying certain alleles do not benefit from drug therapy due to ultrarapid metabolism caused by multiple genes or by induction of gene expression or, alternatively, suffer from adverse effects of the drug treatment due to the presence of defective alleles. It is likely that future predictive genotyping for such enzymes might benefit 15-25% of drug treatments, and thereby allow prevention of adverse drug reactions and causalities, and thus improve the health of a significant fraction of the patients.

Effects of N-acetylcysteine on ethanol-induced hepatotoxicity in rats fed via total enteral nutrition.

The effects of the dietary antioxidant N-acetylcysteine (NAC) on alcoholic liver damage were examined in a total enteral nutrition (TEN) model of ethanol toxicity in which liver pathology occurs in the absence of endotoxemia. Ethanol treatment resulted in steatosis, inflammatory infiltrates, occasional foci of necrosis, and elevated ALT in the absence of increased expression of the endotoxin receptor CD 14, a marker of Kupffer cell activation by LPS. In addition, ethanol treatment induced CYP 2 E1 and increased TNFalpha and TGFbeta mRNA expression accompanied by suppressed hepatic IL-4 mRNA expression.

CYP3A7 protein expression is high in a fraction of adult human livers and partially associated with the CYP3A7*1C allele.

Previously, cytochrome P450 3A7 (CYP3A7), which constitutes the major CYP enzyme in fetal livers, has been considered a fetus-specific enzyme. However, CYP3A7 mRNA has recently been shown to be expressed at significant levels in a subset of adult human livers, several of which carry the CYP3A7*1C allele that contains the proximal PXR/CAR element of CYP3A4. The objective of this study was to investigate CYP3A7 expression at the protein level by developing a CYP3A7-specific antibody to allow its quantification.

Metabolic gene polymorphisms and lung cancer risk in non-smokers. An update of the GSEC study.

Background: Since genetic factors may play an important role in lung cancer development at low dose carcinogen exposure, non-smokers are a good model to study genetic susceptibility and its interaction with environmental factors.

Materials And Methods: We evaluated the role of the metabolic gene polymorphisms CYP1A1MspI, CYP1A1Ile462Val, GSTM1, and GSTT1 in non-smoker lung cancer patients from the International Collaborative Study on Genetic Susceptibility to Environmental Carcinogens (GSEC). Non-smokers (defined as subjects who never smoked on a regular basis) were selected from the GSEC database.

The human genome project and novel aspects of cytochrome P450 research.

Currently, 57 active cytochrome P450 (CYP) genes and 58 pseudogenes are known to be present in the human genome. Among the genes discovered by initiatives in the human genome project are CYP2R1, CYP2W1, CYP2S1, CYP2U1 and CYP3A43, the latter apparently encoding a pseudoenzyme. The function, polymorphism and regulation of these genes are still to be discovered to a great extent.

Novel extrahepatic cytochrome P450s.

The cytochrome P450 enzymes are highly expressed in the liver and are involved in the metabolism of xenobiotics. Because of the initiatives associated with the Human Genome Project, a great progress has recently been seen in the identification and characterization of novel extrahepatic P450s, including CYP2S1, CYP2R1, CYP2U1 and CYP2W1. Like the hepatic enzymes, these P450s may play a role in the tissue-specific metabolism of foreign compounds, but they may also have important endogenous functions.

Characterization of common CYP1B1 variants with different capacity for benzo[a]pyrene-7,8-dihydrodiol epoxide formation from benzo[a]pyrene.

Cytochrome P450 1B1 (CYP1B1), an extrahepatic enzyme inducible by smoking, is overexpressed in many tumors and catalyzes the metabolic activation of procarcinogens such as polycyclic aromatic hydrocarbons. In human, CYP1B1 is genetically polymorphic and five common missense mutations causing amino acid substitution have been identified. In this study, we have investigated CYP1B1 haplotypes present in a Spanish population and carried out functional analyses of the corresponding enzymes in yeast using benzo[a]pyrene as a substrate.

A novel polymorphic cytochrome P450 formed by splicing of CYP3A7 and the pseudogene CYP3AP1.

The cytochrome P450 3A7 (CYP3A7) is the most abundant CYP in human liver during fetal development and first months of postnatal age, playing an important role in the metabolism of endogenous hormones, drugs, differentiation factors, and potentially toxic and teratogenic substrates. Here we describe and characterize a novel enzyme, CYP3A7.1L, encompassing the CYP3A7.

Identification and phenotype characterization of two CYP3A haplotypes causing different enzymatic capacity in fetal livers.

Background: The fetal liver cytochrome P450 (CYP) 3A enzymes metabolize potentially toxic and teratogenic substrates and drugs in addition to endogenous hormones and differentiation factors. CYP3A7 is the most abundant CYP in the human liver during fetal stages and the first months of postnatal age and shows a large interindividual variability of unknown molecular basis.

Methods: A new variant gene (CUpsilonP3A7*2), which carries a mutation in exon 11 of CUpsilonP3A7 causing a T409R substitution, was identified by direct sequencing.

Substrate specific metabolism by polymorphic cytochrome P450 2D6 alleles.

A comparative metabolism study was performed for bufuralol, dextromethorphan, imipramine, mianserin, sparteine, tamoxifen, haloperidol and two drug candidates (Rec27/0110 and Rec15/2739) on V79 cells genetically engineered to express human cytochrome P450 (CYP) variants 2D6*1, 2D*2, 2D*9 and 2D*17. Unexpectedly, the CYP2D6*17 dependent metabolism profile of haloperidol and Rec27/0110 were found to differ from all other substrates tested. Some of these known standard substrates are frequently applied in marker reactions for CYP2D6 and with these standard substrates, CYP2D6*1 is known to be the most active form.

Activation of c-fos by lipopolysaccharide in glial cells via p38 mitogen-activated protein kinase-dependent activation of serum or cyclic AMP/calcium response element.

Pathological conditions such as ischaemic stroke and inflammatory disorders cause c-fos activation in the brain. This activation contributes to the initiation of the brain's inflammatory response, orchestrated by activated glial cells. The inflammatory signalling cascades leading to c-fos activation in glial cells are not well characterized.

Transcriptional regulation of the human CYP2A6 gene.

Nicotine C-oxidation is primarily catalyzed by CYP2A6 in humans. This enzymatic activity exhibits a large interindividual variability, which to a great extent is caused by genetic polymorphisms in the CYP2A6 gene. There are large interindividual differences in CYP2A6 mRNA and protein levels, but little is known about the transcriptional regulation of CYP2A6, which can, e.

New approaches and applications in chemical biology.

The 15th International Symposium on Microsomes and Drug Oxidations: Chemical Biology in the Postgenomic Era--New Approaches and Applications in Mainz, Germany, July 4-9, 2004, had 570 attendees and was nicely organized by Franz and Barbara Oesch and colleagues. At the meeting, 73 different lectures were presented and about 240 posters were shown. This review discusses most of the lectures presented at the Symposium.

Characterization and partial purification of the rat and human enzyme systems active in the reduction of N-hydroxymelagatran and benzamidoxime.

The enzymic basis for intracellular reduction of N-hydroxylated amidines to their corresponding amidines, and hydroxylamines to their corresponding amines, is unknown. The hydroxylated amidines can be used as prodrug moieties, and an understanding of the enzyme system active in the reduction can contribute to more efficient drug development. In this study, we examined the properties of this enzyme system using benzamidoxime and N-hydroxymelagatran as substrates.

CYPalleles: a web page for nomenclature of human cytochrome P450 alleles.

Genetic variations in the genes encoding the cytochrome P450s (CYPs) are important determinants for interindividual differences in sensitivity to drugs and environmental chemicals as well as for the pathogenesis of several human diseases. In order to standardise the nomenclature of the rapidly increasing number of alleles described, a web page was established a few years ago. Here, we describe the present status of the web page and summarise the principles used for CYP allele nomenclature.

Genetic polymorphisms of cytochrome P450 2D6 (CYP2D6): clinical consequences, evolutionary aspects and functional diversity.

CYP2D6 is of great importance for the metabolism of clinically used drugs and about 20-25% of those are metabolised by this enzyme. In addition, the enzyme utilises hydroxytryptamines as endogenous substrates. The polymorphism of the enzyme results in poor, intermediate, efficient or ultrarapid metabolisers (UMs) of CYP2D6 drugs.

Use of molecular simulation for mapping conformational CYP2E1 epitopes.

The identification of the epitopes recognized by autoantibodies against cytochrome P450s (CYPs) associated with drug-induced hepatotoxicity is difficult because of their conformational nature. In the present investigation, we used a novel approach based on the analysis of the whole molecule antigenic capacity following single amino acid substitutions to identify the conformational epitopes on CYP2E1. A molecular model of CYP2E1 was generated based on the CYP2C5 crystal structure, and potential motifs for amino acid exchanges were selected by computer simulation in the surface of alpha helices and beta sheets.

Regulation of aryl hydrocarbon receptor signal transduction by protein tyrosine kinases.

The involvement of protein tyrosine kinases (PTKs) in aryl hydrocarbon receptor (AhR)-mediated signalling by omeprazole and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was investigated in hepatoma cells. Both omeprazole- and TCDD-dependent AhR signalling was attenuated by inhibition of c-src kinase, either by using pyrazolopyrimidine 4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4 ]pyrimidine (PP1) and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) inhibitors or by expression of dominant-negative c-src. These results indicate that the overall AhR function is modulated by c-src kinase activity.

Cytochrome P450 1B1 gene polymorphisms and postmenopausal endometrial cancer risk.

Estrogen unopposed by progestins is a key factor in endometrial cancer etiology. Cytochrome P450 1B1 (CYP1B1), responsible for the 4-hydroxylation of estrogen, may be important in endometrial carcinogenesis, either as a regulator of estrogen availability or as a producer of potentially genotoxic estrogen metabolites. We investigated the association of CYP1B1 genotype and endometrial cancer risk in a population-based case-control study of postmenopausal Swedish women.

Polymorphic NF-Y dependent regulation of human nicotine C-oxidase (CYP2A6).

Objectives: In humans, cytochrome P450 2A6 (CYP2A6) constitutes the principal nicotine C-oxidase. Several different polymorphic CYP2A6 gene variants are known which contribute to the highly variable expression of this enzyme among individuals. In this study we report a novel polymorphism located in the 5' flanking region (-745A > G) of the CYP2A6 gene disrupting a CCAAT box.

Dietary long-chain n-3 fatty acids for the prevention of cancer: a review of potential mechanisms.

Increasing evidence from animal and in vitro studies indicates that n-3 fatty acids, especially the long-chain polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid, present in fatty fish and fish oils inhibit carcinogenesis. The epidemiologic data on the association between fish consumption, as a surrogate marker for n-3 fatty acid intake, and cancer risk are, however, somewhat less consistent. This review highlights current knowledge of the potential mechanisms of the anticarcinogenic actions of n-3 fatty acids.

Lack of sexual dimorphism in alcohol-induced liver damage (ALD) in rats treated chronically with ethanol-containing low carbohydrate diets: The role of ethanol metabolism and endotoxin.

Evidence has been presented suggesting that females are significantly more susceptible to alcohol-induced liver damage (ALD) than males. In the current study, we examined sexual dimorphism in hepatic pathology, metabolism and cytokine profiles using two different rat models of ALD. Male and female Sprague-Dawley or Wistar rats were fed ethanol-containing low-carbohydrate liquid diets using oral or intragastric methods for 42 or 60 days.

Association of metabolic gene polymorphisms with tobacco consumption in healthy controls.

Polymorphisms in genes that encode for metabolic enzymes have been associated with variations in enzyme activity between individuals. Such variations could be associated with differences in individual exposure to carcinogens that are metabolized by these genes. In this study, we examine the association between polymorphisms in several metabolic genes and the consumption of tobacco in a large sample of healthy individuals.

Pharmacogenetics of cytochrome P450 and its applications in drug therapy: the past, present and future.

The field of cytochrome P450 pharmacogenetics has progressed rapidly during the past 25 years. All the major human drug-metabolizing P450 enzymes have been identified and cloned, and the major gene variants that cause inter-individual variability in drug response and are related to adverse drug reactions have been identified. This information now provides the basis for the use of predictive pharmacogenetics to yield drug therapies that are more efficient and safer.

Alcoholic liver disease in rats fed ethanol as part of oral or intragastric low-carbohydrate liquid diets.

The intragastric administration of ethanol as part of a low-carbohydrate diet results in alcohol hepatotoxicity. We aimed to investigate whether comparable liver injury can be achieved by oral diet intake. Male Sprague-Dawley rats were fed ethanol as part of low-carbohydrate diets for 36-42 days either intragastrically or orally.