Genetic polymorphisms of cytochrome P4502E1 related to the development of alcoholic liver disease

Dietary cholesterol in alcohol-associated liver disease

There is an increasing prevalence of alcohol-associated liver disease (ALD) worldwide. In addition to excessive alcohol consumption, other nutritional factors have been shown to affect the initiation and progression of ALD. The emerging role of cholesterol in exacerbating ALD has been reported recently and the underlying mechanisms are discussed. In addition, the interplay between dietary cholesterol and alcohol on cholesterol metabolism is reviewed. Furthermore, we highlight the therapeutic potential of cholesterol-lowering drugs in managing the onset and severity of ALD. Finally, we suggest the future mechanistic investigation of the effect of cholesterol on insulin resistance and intestinal inflammation in the exacerbation of alcohol-induced cellular and systemic dysfunction.

Hepatic, Extrahepatic and Extracellular Vesicle Cytochrome P450 2E1 in Alcohol and Acetaminophen-Mediated Adverse Interactions and Potential Treatment Options

Alcohol and several therapeutic drugs, including acetaminophen, are metabolized by cytochrome P450 2E1 (CYP2E1) into toxic compounds. At low levels, these compounds are not detrimental, but higher sustained levels of these compounds can lead to life-long problems such as cytotoxicity, organ damage, and cancer. Furthermore, CYP2E1 can facilitate or enhance the effects of alcohol-drug and drug-drug interactions. In this review, we discuss the role of CYP2E1 in the metabolism of alcohol and drugs (with emphasis on acetaminophen), mediating injury/toxicities, and drug-drug/alcohol-drug interactions. Next, we discuss various compounds and various nutraceuticals that can reduce or prevent alcohol/drug-induced toxicity. Additionally, we highlight experimental outcomes of alcohol/drug-induced toxicity and potential treatment strategies. Finally, we cover the role and implications of extracellular vesicles (EVs) containing CYP2E1 in hepatic and extrahepatic cells and provide perspectives on the clinical relevance of EVs containing CYP2E1 in intracellular and intercellular communications leading to drug-drug and alcohol-drug interactions. Furthermore, we provide our perspectives on CYP2E1 as a druggable target using nutraceuticals and the use of EVs for targeted drug delivery in extrahepatic and hepatic cells, especially to treat cellular toxicity.

Genetic Variants of Alcohol Metabolizing Enzymes and Alcohol-Related Liver Cirrhosis Risk

Alcohol-related liver disease (ARLD) is a major public health issue caused by excessive alcohol consumption. ARLD encompasses a wide range of chronic liver lesions, alcohol-related liver cirrhosis being the most severe and harmful state. Variations in the genes encoding the enzymes, which play an active role in ethanol metabolism, might influence alcohol exposure and hence be considered as risk factors of developing cirrhosis. We conducted a case-control study in which 164 alcohol-related liver cirrhosis patients and 272 healthy controls were genotyped for the following functional single nucleotide variations (SNVs): ADH1B gene, rs1229984, rs1041969, rs6413413, and rs2066702; ADH1C gene, rs35385902, rs283413, rs34195308, rs1693482, and rs35719513; CYP2E1 gene, rs3813867. Furthermore, copy number variations (CNVs) for ADH1A, ADH1B, ADH1C, and CYP2E1 genes were analyzed. A significant protective association with the risk of developing alcohol-related liver cirrhosis was observed between the mutant alleles of SNVs ADH1B rs1229984 (P_c value = 0.037) and ADH1C rs283413 (P_c value = 0.037). We identified CNVs in all genes studied, ADH1A gene deletions being more common in alcohol-related liver cirrhosis patients than in control subjects, although the association lost statistical significance after multivariate analyses. Our findings support that susceptibility to alcohol-related liver cirrhosis is related to variations in alcohol metabolism genes.

Alcoholic Liver Disease: Alcohol Metabolism, Cascade of Molecular Mechanisms, Cellular Targets, and Clinical Aspects

Alcoholic liver disease is the result of cascade events, which clinically first lead to alcoholic fatty liver, and then mostly via alcoholic steatohepatitis or alcoholic hepatitis potentially to cirrhosis and hepatocellular carcinoma. Pathogenetic events are linked to the metabolism of ethanol and acetaldehyde as its first oxidation product generated via hepatic alcohol dehydrogenase (ADH) and the microsomal ethanol-oxidizing system (MEOS), which depends on cytochrome P450 2E1 (CYP 2E1), and is inducible by chronic alcohol use. MEOS induction accelerates the metabolism of ethanol to acetaldehyde that facilitates organ injury including the liver, and it produces via CYP 2E1 many reactive oxygen species (ROS) such as ethoxy radical, hydroxyethyl radical, acetyl radical, singlet radical, superoxide radical, hydrogen peroxide, hydroxyl radical, alkoxyl radical, and peroxyl radical. These attack hepatocytes, Kupffer cells, stellate cells, and liver sinusoidal endothelial cells, and their signaling mediators such as interleukins, interferons, and growth factors, help to initiate liver injury including fibrosis and cirrhosis in susceptible individuals with specific risk factors. Through CYP 2E1-dependent ROS, more evidence is emerging that alcohol generates lipid peroxides and modifies the intestinal microbiome, thereby stimulating actions of endotoxins produced by intestinal bacteria; lipid peroxides and endotoxins are potential causes that are involved in alcoholic liver injury. Alcohol modifies SIRT1 (Sirtuin-1; derived from Silent mating type Information Regulation) and SIRT2, and most importantly, the innate and adapted immune systems, which may explain the individual differences of injury susceptibility. Metabolic pathways are also influenced by circadian rhythms, specific conditions known from living organisms including plants. Open for discussion is a 5-hit working hypothesis, attempting to define key elements involved in injury progression. In essence, although abundant biochemical mechanisms are proposed for the initiation and perpetuation of liver injury, patients with an alcohol problem benefit from permanent alcohol abstinence alone.

Genetic Association and Gene-Gene Interaction Reveal Genetic Variations in ADH1B, GSTM1 and MnSOD Independently Confer Risk to Alcoholic Liver Diseases in India

Genetic susceptibility is an important modifier of clinical outcome and natural history of progression in Alcoholic liver disease (ALD). While the significance of ethnicity in this evolution is very clear, subtle inter-individual genetic variant(s) might be important and thus we investigated those in an Indian population. Fourteen markers were genotyped within two alcohol metabolism genes [Alcohol dehydrogenase (ADH) gene clusters (ADH1B and ADH1C) and Aldehyde dehydrogenase (ALDH2)], one microsomal ethanol oxidizing enzyme cytochrome p450 (CYP2E1) and three oxidative stress response (OSR) genes (MnSOD, GSTT1 and GSTM1) among 490 Bengali individuals (322 ALD and 168 control) from Eastern and North-Eastern India and validation was performed in a new cohort of 150 Bengali patients including 100 ALD and 50 advanced non-alcoholic steatohepatitis (NASH). Out of 14 genetic variants, carriage of 5 genotypes (rs2066701CC in ADH1B, rs1693425TT in ADH1C, rs4880TT in MnSOD and GSTT1/GSTM1 null, p-value <0.05) were noted significantly higher among ALD patients while inter or intra group gene-gene interaction analysis revealed that addition of risk genotype of any OSR gene enhanced the possibility of ALD synergistically. Multiple logistic regression analysis showed independent association of rs2066701CC, rs4880TT and GSTM1 null genotype with ALD while lower frequencies of those genotypes in advanced NASH patients further confirmed their causal relation to ALD. Thus these findings suggest that the three variants of ADH1C, MnSOD and GSTM1 can be used to identify individuals who are at high risk to develop ALD and may be helpful in proper management of Indian alcoholics.

Polymorphisms in the human cytochrome P450 and arylamine N-acetyltransferase: susceptibility to head and neck cancers

The occurrence of head and neck cancer (HNC) is associated with smoking and alcohol drinking. Tobacco smoking exposes smokers to a series of carcinogenic chemicals. Cytochrome P450 enzymes (CYP450s), such as CYP1A1, CYP1B1, and CYP2D6, usually metabolize carcinogens to their inactive derivatives, but they occasionally convert the chemicals to more potent carcinogens. In addition, via CYP450 (CYP2E1) oxidase, alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Furthermore, two N-acetyltransferase isozymes (NATs), NAT1 and NAT2, are polymorphic and catalyze both N-acetylation and O-acetylation of aromatic and heterocyclic amine carcinogens. Genetic polymorphisms are associated with a number of enzymes involved in the metabolism of carcinogens important in the induction of HNC. It has been suggested that such polymorphisms may be linked to cancer susceptibility. In this paper, we select four cytochrome P450 enzymes (CYP1A1, CYP1BA1, CYP2D6, and CYP2E1), and two N-acetyltransferase isozymes (NAT1 and NAT2) in order to summarize and analyze findings from the literature related to HNC risk by focusing on (i) the interaction between these genes and the environment, (ii) the impact of genetic defect on protein activity and/or expression, and (iii) the eventual involvement of race in such associations.

Cytochrome P450 2E1 gene polymorphisms/haplotypes and anti-tuberculosis drug-induced hepatitis in a Chinese cohort

Objective

The pathogenic mechanism of anti-tuberculosis (anti-TB) drug-induced hepatitis is associated with drug metabolizing enzymes. No tagging single-nucleotide polymorphisms (tSNPs) of cytochrome P450 2E1(CYP2E1) in the risk of anti-TB drug-induced hepatitis have been reported. The present study was aimed at exploring the role of tSNPs in CYP2E1 gene in a population-based anti-TB treatment cohort.

Methods and Design

A nested case-control study was designed. Each hepatitis case was 14 matched with controls by age, gender, treatment history, disease severity and drug dosage. The tSNPs were selected by using Haploview 4.2 based on the HapMap database of Han Chinese in Beijing, and detected by using TaqMan allelic discrimination technology.

Results

Eighty-nine anti-TB drug-induced hepatitis cases and 356 controls were included in this study. 6 tSNPs (rs2031920, rs2070672, rs915908, rs8192775, rs2515641, rs2515644) were genotyped and minor allele frequencies of these tSNPs were 21.9%, 23.0%, 19.1%, 23.6%, 20.8% and 44.4% in the cases and 20.9%, 22.7%, 18.9%, 23.2%, 18.2% and 43.2% in the controls, respectively. No significant difference was observed in genotypes or allele frequencies of the 6 tSNPs between case group and control group, and neither of haplotypes in block 1 nor in block 2 was significantly associated with the development of hepatitis.

Conclusion

Based on the Chinese anti-TB treatment cohort, we did not find a statistically significant association between genetic polymorphisms of CYP2E1 and the risk of anti-TB drug-induced hepatitis. None of the haplotypes showed a significant association with the development of hepatitis in Chinese TB population.

Genetic polymorphisms of CYP2E1 and DNA repair genes HOGG1 and XRCC1: association with hepatitis B related advanced liver disease and cancer

A population based case-control study was designed to explore the genetic risk factors for hepatitis B virus (HBV) related liver disease susceptibility. A total of 424 subjects comprising 210 controls, 50 acute HBV (AVH), 84 chronic HBV (CHBV), 25 HBV related cirrhosis and 55 HBV related hepatocellular carcinoma (HCC) cases were included in the study. PCR-RFLP was used for the genotyping of Cyp2E1*5B, hOGG1 codon 326 and XRCC1 codon 399. Compared to controls, Cyp2E1 rsaI variant c2 genotype increased the risk of HBV related liver disease severity by 2.68 fold, the highest for HCC cases (3.981 folds, p=0.106); and was associated with higher histology activity index (HAI) (p<0.001) in CHBV patients. Cyp2E1 and hOGG1 variants were independently associated with a significantly higher fibrosis score in CHBV group. Analysis of gene-gene interaction studies showed an increased risk of HCC, cirrhosis and CHBV in a Cyp2E1 variant+XRCC1 variant combination (p<0.001); and hOGG1 variants+XRCC1 variants. A mutually independent heterozygous hOGG1 and XRCC1 combination resulted in a decreased risk of HBV related liver disease. On the other hand, a wild-type hOGG1 and XRCC1 combination was associated with a significantly higher risk of AVH (p=0.010) but a lower risk of CHBV (p=0.032) and HCC (p=0.006). The gene-gene interactions were also associated with a significant increase in HAI and fibrosis score in CHBV patients. Cyp2E1, hOGG1 and XRCC1 genotypes significantly alter the risk of HBV related liver disease susceptibility and severity, independently or through gene-gene interaction.

Roles of cytochrome P4502E1 gene polymorphisms and the risks of alcoholic liver disease: a meta-analysis

Background

Previous studies investigating the association between cytochrome P4502E1 (CYP2E1) polymorphisms and the risk of alcoholic liver diseases (ALD) have yielded conflicting results. Thus, a meta-analysis was performed to clarify the association between CYP2E1 polymorphisms and the risks of ALD.

Methods

A comprehensive literature search was conducted to identify the relevant studies. The fixed or random effect model was selected based on the heterogeneity test among studies. Publication bias was estimated using Begg’s funnel plots and Egger’s regression test.

Results

A total of 27 and 9 studies were finally included for the association between the CYP2E1 Pst I/Rsa I or Dra I polymorphisms and the risks of ALD, respectively. Overall, the combined results showed that homozygous genotype c2c2 was significantly associated with increase risk of ALD in worldwide populations (c2c2 vs. c1c1: OR = 3.12, 95%CI 1.91–5.11) when ALD patients were compared with alcoholics without ALD. Significant associations between CYP2E1 Pst I/Rsa I polymorphism and ALD risk were also observed in Asians (c2c2 vs. c1c1: OR = 4.11, 95%CI 2.32–7.29) and in Caucasians (c2c2/c1c2 vs. c1c1: OR = 1.58, 95%CI 1.04–2.42) when ALD patients were compared with alcoholics without ALD. However, subgroup analysis stratified by ALD types showed that CYP2E1 Pst I/Rsa I polymorphism was not significantly associated with the risks of alcoholic cirrhosis (ALC). No significant association was observed between CYP2E1 Dra I polymorphism and ALD risks.

Conclusion

This meta-analysis suggested that CYP2E1 Pst I/Rsa I polymorphism might be not significantly associated with advanced form of ALD (ALC), but might be significantly associated with other form of ALD such as steatosis, hepatisis, fibrosis. Furthermore, CYP2E1 Dra I polymorphism might be not significantly associated with the ALD risks. Since potential confounders could not be ruled out completely, further studies were needed to confirm these results.

Polymorphisms in the CYP2E1 and GSTM1 genes as possible protection factors for leprosy patients

Background

The CYP2E1 and GSTM1 genes encode metabolic enzymes that have key functions in drug modification and elimination.

Methodology/Principal Findings

We investigated the possible effects of CYP2E1 and GSTM1 polymorphisms in 71 leprosy patients and in 110 individuals from the general population. The GSTM1*0 null allele and INDEL CYP2E1*1D mutant genotypes were analyzed by conventional PCR, while CYP2E1 SNPs (1053C>T, 1293G>C and 7632T>A) were determined by RT-PCR. In leprosy patients, the GSTM1*0 and CYP2E1*5 alleles and the combined alleles GSTM1*0/CYP2E1*6 and GSTM1*0/CYP2E1*5 were significantly related to a baciloscopic index (BI) (BI<3), while the CYP2E1*6 allele was related to a better clinical evolution in the leprosy spectrum.

Conclusions/Significance

Therefore, GSTM1*0, CYP2E1*5 and CYP2E1*6 may be possible protection factors for leprosy patients.

Genetic polymorphisms in alcohol metabolizing enzymes as related to sensitivity to alcohol-induced health effects

Three hundred sixty-seven middle-aged Japanese men were analyzed for genotypes of low K(m) aldehyde dehydrogenase (ALDH2) and cytochrome P450 2E1, and for the association with alcohol-induced health effects. Homozygotes for the normal ALDH2 gene (NN) and for the mutant gene (MM) and heterozygotes (NM) were found in 60, 6 and 33%, and homozygotes for the c1 gene (c1/1) and c2 gene (c2/2) of P450 2E1, and heterozygotes (c1/2) in 55, 5 and 40% of subjects, respectively. Mean alcohol consumption significantly differed in the three ALDH2 genotypes: 297 g per week in NN, 158 g in NM and 18 g in MM. It was not different in the three P450 2E1 genotypes, but tended to increase from cl/1 to c2/2 in the NN subjects while there was an inverse relationship in the subjects having the M gene. No difference in alcohol-induced health effects was observed in ALDH2 genotypes, but c2/2 genotype showed higher blood pressure and serum uric acid than the other P450 2E1 genotypes in the subjects consuming 200 g or more of alcohol per week. These results suggest an interactive effect of ALDH2 and P450 2E1 genes on alcohol consumption and a higher sensitivity to alcohol-induced health effects in c2/2 genotypes, although larger scale studies are required to confirm these findings.

Dual effects of sodium butyrate on hepatocellular carcinoma cells

Sodium butyrate (NaBu), a histone deacetylase inhibitor, has been shown to inhibit cell growth, induce cell differentiation and apoptosis in multiple cell lines. In present study, we revealed the dual effects of NaBu in regulating hepatocellular carcinoma (HCC) cells. In two different HCC cell lines, SK-Hep1 and SMMC-7721, low concentrations of NaBu induced a significant increase in cell growth ratio and S-phase cell percentage, accompanied by a reduced p21 Cip1 expression at both mRNA and protein levels, while dissimilarly, high concentrations of NaBu inhibited cell growth and induced G1 arrest through up-regulation of p21 Cip1 and p27 Kip1 protein expression. The reduction of p45 Skp2 expression further indicated that the ubiquitin-mediated protein degradation might play a role in NaBu-induced up-regulation of p21 Cip1 and p27 Kip1. Moreover, the high concentration of NaBu was also able to trigger HCC cell apoptosis. Taken together, these results demonstrate the distinct effects of NaBu at different dosages. This finding may contribute to develop more effective tumor therapeutic protocols of NaBu in HCC.

Bio-informatics based analysis of genes implicated in alcohol mediated liver injury

Alcohol induced liver injury has been studied extensively. Using literature search and bioinformatics tools, the present study characterizes the genes involved in alcohol induced liver injury. The cellular and metabolic processes in which genes involved in alcohol induced liver injury are implicated are also discussed. The genes related to alcohol induced liver injury are also involved in affecting certain molecular functions and metabolism of drugs, besides being associated with diseases. In conclusion, the changes in regulation of genes implicated in alcohol induced liver injury apart from causing alcohol mediated hepatic dysfunction may affect other vital processes in the body.

Oral cancer and polymorphism of ethanol metabolising genes

Oral cancer is the sixth most common cancer worldwide and a major health problem in some parts of the world. Epidemiological studies have shown that habitual alcohol consumption could be a risk factor in oral carcinogenesis, although the true involvement of alcohol is unknown. Via alcohol dehydrogenase (ADH) and cytochrome P450 oxidase (CYP) alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Subsequently, and during the metabolizing process, acetaldehyde becomes acetate by acetaldehyde dehydrogenase (ALDH). Therefore, acetaldehyde levels are determined mainly by the action of ADH, CYP and ALDH. Recently, several studies have found that certain polymorphisms of genes encoding these enzymes confer a higher or lower metabolic activity and therefore different risk for certain malignancies such as oral cancer. In this review, we analyze the polymorphisms of alcohol metabolising enzymes in relation susceptibility to an oral cancer.

Nitric oxide and redox regulation in the liver: Part I. General considerations and redox biology in hepatitis

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are created in normal hepatocytes and are critical for normal physiologic processes, including oxidative respiration, growth, regeneration, apoptosis, and microsomal defense. When the levels of oxidation products exceed the capacity of normal antioxidant systems, oxidative stress occurs. This type of stress, in the form of ROS and RNS, can be damaging to all liver cells, including hepatocytes, Kupffer cells, stellate cells, and endothelial cells, through induction of inflammation, ischemia, fibrosis, necrosis, apoptosis, or through malignant transformation by damaging lipids, proteins, and/or DNA. In Part I of this review, we will discuss basic redox biology in the liver, including a review of ROS, RNS, and antioxidants, with a focus on nitric oxide as a common source of RNS. We will then review the evidence for oxidative stress as a mechanism of liver injury in hepatitis (alcoholic, viral, nonalcoholic). In Part II of this review, we will review oxidative stress in common pathophysiologic conditions, including ischemia/reperfusion injury, fibrosis, hepatocellular carcinoma, iron overload, Wilson's disease, sepsis, and acetaminophen overdose. Finally, biomarkers, proteomic, and antioxidant therapies will be discussed as areas for future therapeutic interventions.

Cytochrome P450 2E1 and head and neck cancer: interaction with genetic and environmental risk factors

The present case-control study investigates the association of polymorphisms in cytochrome P450 2E1 (CYP2E1), involved in the metabolism of tobacco carcinogens and alcohol, with Head and Neck Squamous Cell Carcinoma (HNSCC). In addition, the interaction of CYP2E1 (CYP2E1*5B and CYP2E1*6) with other genetic factors (null genotype of glutathione-S-Transferase M1, GSTM1, X-Ray Repair Cross Complementing Group I, XRCC1 (Arg194Trp), and environmental risk factors such as alcohol and tobacco in modifying HNSCC risk were investigated. Genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in a total of 350 male cases of HNSCC and an equal number of healthy male controls. Statistical analysis showed a significant increase in HNSCC risk in cases with variant genotypes of CYP2E1*5B (RsaI) (O.R. 3.44; 95% C.I. 1.45-8.14) and CYP2E1*6 (DraI) (O.R. 1.76; 95% C.I. 1.28-2.41). Haplotype analysis revealed that haplotype T-A was associated with a greater than 10-fold increase in risk for HNSCC. Our data also revealed a several fold increase in HNSCC risk in cases carrying a combination of variant genotypes of CYP2E1 with the null genotype of GSTM1 or XRCC1 variant genotypes. Alcohol or tobacco use (both smoking and chewing) were also found to interact with variant genotypes of CYP2E1 in significantly enhancing HNSCC risk. This increase in risk associated with an interaction of CYP2E1 genotypes with GSTM1 or XRCC1 or with tobacco and alcohol use demonstrates the importance of gene-gene and gene-environment interactions in the development of HNSCC.

Polymorphism in cytochrome P450 2E1 and interaction with other genetic risk factors and susceptibility to alcoholic liver cirrhosis

The association of polymorphism in cytochrome P450 2E1 (CYP2E1), the major microsomal ethanol metabolizing enzyme and its interaction with genes, involved in detoxification of reactive oxygen species, such as glutathione-S-transferases M1 (GSTM1) and alcohol intake, gamma-aminobutyric acid receptor gamma2 (GABRG2) was studied with the risk to alcoholic cirrhosis in a case-control study. A total of 160 alcoholic cirrhotic and 125 non-alcoholic cirrhotic cases, visiting the OPD facility of Gastroenterology Department of Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGI), Lucknow, India and 250 non-alcoholic and 100 alcoholic controls having no evidence of liver disease were included in the study. PCR-based RFLP methodology was followed for genotyping studies. Our data revealed that the variant genotypes of CYP2E1 5B exhibited significant association with the alcoholic liver cirrhosis when compared to non-alcoholic controls (OR: 4.3; 95%CI: 1.5-12.4; p: 0.003) or non-alcoholic cirrhosis patients (OR: 5.4; 95%CI: 1.2-24.5; p: 0.01) or alcoholic controls (OR: 4.3; 95%CI: 0.95-19.62; p: 0.04). Haplotype approach revealed that haplotype T-A-T was found to be associated with more than 5-fold increase in risk for alcoholic cirrhosis. Likewise, combination of variant genotype of CYP2E1 5B with null genotype of GSTM1, a phase II detoxification enzyme, resulted in several fold increase in risk in alcoholic cirrhotic patients when compared with non-alcoholic controls or non-alcoholic cirrhotic patients. Further, the combination of variant genotype of CYP2E1 5B with GABRG2, significantly increased the risk upto 6.5-fold in alcoholic cirrhotic patients when compared with non-alcoholic controls thereby suggesting the role of gene-gene interaction in alcoholic cirrhosis.

Polymorphism in glutathione-S-transferases: a risk factor in alcoholic liver cirrhosis

In a case-control study, association of polymorphism in glutathione-S-transferases (GSTM1, GSTT1, GSTP1), involved in detoxification of reactive oxygen species (ROS), was studied with alcoholic liver cirrhosis. The study included 175 alcoholic cirrhotic patients (ACPs), 140 non-alcoholic cirrhotic patients (NACPs), visiting Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGI), Lucknow, India, 255 non-alcoholic controls and 140 alcoholic controls. The data showed an increase in risk to alcoholic cirrhosis in ACPs with GSTM1 (null) genotype when compared with non-alcoholic controls (OR: 1.7; 95% CI: 1.15-2.56) or alcoholic controls (OR: 1.7; 95% CI: 1.07-2.73). Significant increase in risk was also observed in ACPs with variant genotype of GSTP1 when compared with non-alcoholic controls (OR: 1.65; 95% CI: 1.12-2.43). A much higher risk to alcoholic liver cirrhosis was observed in patients carrying combination of null genotypes of GSTM1 and GSTT1 (OR: 2.8; 95% CI: 1.3-6.06) or variant genotype of GSTP1 and null genotype of GSTM1 (OR: 2.8; 95% CI: 1.58-4.90) or GSTT1 (OR: 2.16; 95% CI: 1.08-4.28). Likewise, greater risk for alcoholic cirrhosis was observed in patients carrying combination of GSTM1, GSTT1 (null) and variant genotype of GSTP1 (OR: 5.8; 95% CI: 2.17-15.80). Our data further showed that interaction of GSTs with variant genotype of manganese superoxide dismutase (MnSOD), which detoxifies free radicals, or cytochrome P450 2E1, which generates free radicals, resulted in several fold increase in risk to alcoholic liver cirrhosis in ACPs when compared with non-alcoholic controls thus demonstrating the role of gene-gene interactions in modulating the risk to alcoholic liver cirrhosis.

Genetic polymorphism in CYP2E1: Population distribution of CYP2E1 activity

Cytochrome P-450 2E1 (CYP2E1) is a key enzyme in the metabolic activation of a variety of toxicants including nitrosamines, benzene, vinyl chloride, and halogenated solvents such as trichloroethylene. CYP2E1 is also one of the enzymes that metabolizes ethanol to acetaldehyde, and is induced by recent ethanol ingestion. There is evidence that interindividual variability in the expression and functional activity of this cytochrome (CYP) may be considerable. Genetic polymorphisms in CYP2E1 were identified and linked to altered susceptibility to hepatic cirrhosis induced by ethanol and esophageal and other cancers in some epidemiological studies. Therefore, it is important to evaluate how such polymorphisms affect CYP2E1 function and whether it is possible to construct a population distribution of CYP2E1 activity based upon the known effects of these polymorphisms and their frequency in the population. This analysis is part of the genetic polymorphism database project described in the lead article in this series and followed the approach described in that article (Ginsberg et al., 2009, this issue). Review of the literature found that there are a variety of CYP2E1 variant alleles but the functional significance of these variants is still unclear. Some, but not all, studies suggest that several upstream 5' flanking mutations affect gene expression and response to inducers such as ethanol or obesity. None of the coding-region variants consistently affects enzyme function. Part of the reason for conflicting evidence regarding genotype effect on phenotype may be due to the wide variety of exposures such as ethanol or dietary factors and physiological factors including body weight or diabetes that modulate CYP2E1 expression. In conclusion, evidence is too limited to support the development of a population distribution of CYP2E1 enzyme activity based upon genotypes. Health risk assessments may best rely upon data reporting interindividual variability in CYP2E1 function for input into physiologically based pharmacokinetic (PBPK) models involving CYP2E1 substrates.

CD133+CD44+ population efficiently enriches colon cancer initiating cells

BACKGROUND

Previous reports have demonstrated that CD133(+) cells or CD44(+) cells might be cancer initiating cells (CIC) of colon cancer. However, the association between the two cell types is unclear. In this study, we evaluated the tumorigenicity of each population of human colon cancer divided by CD133 and CD44 using non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice.

METHODS

Using the colon cancer cell lines HT29 and Caco2 we evaluated the change of expression status of CD133 or CD44 by a treatment with sodium butyrate (NaBT) that can induce cellular differentiation. Next, we prepared ten clinical samples of colon cancer and analyzed the expression and tumorigenicity of CD133 and CD44.

RESULTS

With NaBT treatment, CD44 expression was greatly downregulated in both HT29 and Caco2 (HT29: nontreatment versus treatment; 77.8% versus 0.6%, Caco2: 14.0% versus 0.4%, respectively), more than CD133 expression (HT29: nontreatment versus treatment; 90.1% versus 67.7%, Caco2: 98.9% versus 76.3%, respectively). In clinical samples, the percentages of CD133(+) cells and CD44(+) cells varied from 0.3% to 82.0% (mean 35.5%), and from 11.5% to 58.4% (mean 30.0%), respectively. Subcutaneous injection of CD133(+) or CD44(+) cells made a tumor in all mice (3/3 and 4/4, respectively). The combined analysis of CD133 and CD44 revealed that only the CD133(+)CD44(+) population had the ability to produce a tumor (3/3).

CONCLUSION

The findings demonstrate that, at present, the CD133(+)CD44(+ ) population may be the best to identify tumor initiating cells of human colon cancer.

A haplotype analysis of CYP2E1 polymorphisms in relation to alcoholic phenotypes in Mexican Americans

BACKGROUND

Studies regarding the association between the 4 polymorphisms of CYP2E1 (CYP2E1*1D, *5B, *6, and *1B) and alcoholism are inconsistent and inconclusive. The purpose of the present study was to clarify previously discordant studies by haplotype analysis in the Mexican American population.

METHODS

The 4 polymorphisms of CYP2E1 were studied in 334 alcoholics and 365 controls. Genotype, allele, and haplotype frequency comparisons between alcoholics and controls were assessed. Patterns of linkage disequilibrium (LD) at CYP2E1 were determined. Reconstructed haplotypes were tested for associations with clinical phenotypes (age onset of drinking, Maxdrinks, and smoking status).

RESULTS

No significant associations between the 4 polymorphisms of CYP2E1 and alcoholism were revealed by single allele tests. High LD was found between the CYP2E1 c2 and C alleles in Mexican Americans. Eleven haplotypes were present in the 699 participants. The 6 main haplotypes with frequencies higher than 1% made up 97% of the total halpotypes. The frequency of subjects carrying H6 (1C-c2-C-A2) was significantly higher in alcoholics than in controls (p = 0.0001). In contrast, the frequencies of H7 (1C-c2-C-A1) and H10 (1C-c2-D-A1) were significantly lower in alcoholics than in controls (p = 0.0072 for H7 and p = 0.0407 for H10). The frequency of H6 was significantly higher in alcoholics who had late onset of drinking than in nonalcoholic controls. Furthermore, the frequencies of H6 haplotype were also consistently higher in groups who had high number of maximum drinks (9 to 32 drinks) than in controls. When smokers are excluded, the frequencies of H6, H7, and H9 (1C-c2-D-A2) showed statistically significant differences between alcoholics and controls (p < 0.05). Moreover, the association between H6 and alcoholism become more robust when smokers are excluded. Furthermore, the frequency of H1 (1C-c1-D-A2) in alcoholic-smokers was much higher than in alcoholic-nonsmokers (p = 0.0028). In contrast, alcoholic-smokers carried less H2 (1C-c1-D-A1) in comparison with alcoholic-nonsmokers (p = 0.0417). The H3 (1D-c2-C-A2) frequency in alcoholic-smokers was much lower than in alcoholic-nonsmokers (p = 0.0042) and control-smokers (p = 0.0363).

CONCLUSIONS

Our data demonstrate that carrying haplotype H6 might enhance susceptibility to developing alcoholism, but possessing the H7 or H10 haplotype appears to decrease this susceptibility. The H6, H7, and H9 haplotypes may play certain roles in different clinical phenotypes in Mexican American alcoholics. In addition, our data suggest that the H1, H2, and H3 haplotypes are associated with alcohol drinking and smoking. These results support that haplotype analysis is much more informative than single allele analysis. Our findings clearly indicate the importance of H6 haplotype in alcohol drinking in Mexican Americans.

Genetic polymorphisms of drug-metabolizing enzymes and the susceptibility to antituberculosis drug-induced liver injury

Three first-line antituberculosis drugs, isoniazid, rifampicin and pyrazinamide, may induce liver injury, especially isoniazid. This antituberculosis drug-induced liver injury ranges from a mild to severe form, and the associated mortality cases are not rare. The major drug-metabolizing enzyme of isoniazid is N-acetyltransferase. Other possible enzymes are CYP2E1 and glutathione S-transferase. There is evidence that polymorphisms of the genes that encode these enzymes may influence the activity of the corresponding drug-metabolizing enzymes. Recent studies demonstrated that these genetic polymorphisms may be associated with the susceptibility to antituberculosis drug-induced liver injury. The proposed risk-associated genotypes are NAT2 slow acetylator (without wild-type NAT2*4 allele), CYP2E1 *1A/*1A (homozygous wild type) and homozygous null GSTM1 genotype. Although the available data in the field are still limited and warrants further confirmation in different ethnic populations with larger sample sizes, it still cast some light on the application of these pharmacogenetic or pharmacogenomic approaches to prevent grave antituberculosis drug-induced liver injury in the near future.

Alcohol-associated pancreatitis

Only a small proportion of heavy drinking individuals develop pancreatitis. The environmental and host cofactors shown to have an association with alcoholic pancreatitis are smoking and race. The known genetic variations and polymorphisms do not seem to play an important role in alcoholic pancreatitis. Newer developments in the understanding of complex disorders allow clinicians to understand better the role of cofactors and interactions between known and yet unknown environmental and genetic factors in causing alcoholic pancreatitis.

Effects of IFN-alpha on alpha-fetoprotein expressions in hepatocellular carcinoma cells

We investigated the effects of pegylated (PEG)-IFN-alpha2b on alpha-fetoprotein (AFP) expression as demonstrated by protein and mRNA levels in six human hepatocellular carcinoma (HCC) cell lines. The number of KIM-1 cells in culture with PEG-IFN-alpha2b decreased between 24 amd 240 h, whereas the levels of intracellular and secreted AFP per cellular protein increased (except at 192 h), with levels 1.9-fold and 2.9-fold higher at maximum, respectively, than cells without PEG-IFN-alpha2b (control). The mRNA level increased between 72 and 192 h, when the level was 3-fold higher than that of the control. In the 72-h culture with 40-5000 IU/mL PEG-IFN-alpha2b, there were dose-dependent increases in AFP protein and mRNA expression and dose-dependent decrease in cell number resulting from apoptosis and blockage of the cell cycle at the S-phase. The rate of fucosylated AFP in the cell lysate decreased in a dose-dependent and time-dependent manner. In the PEG-IFN-alpha2b culture of the other five HCC cell lines, cell proliferation was suppressed, but the expressions of AFP protein and mRNA increased in only two cell lines, and suppression of cell proliferation was not related to the increase in AFP expressions. Our findings demonstrated that PEG-IFN-alpha2b induces an increase in AFP expression at both the protein and mRNA levels.

-238 G>A polymorphism of tumor necrosis factor alpha gene (TNFA) is associated with alcoholic liver cirrhosis in alcoholic Spanish men

BACKGROUND

The tumor necrosis factor alpha gene (TNFA) has been recently associated to alcoholic steatohepatitis. We have analyzed the distribution of genotypes and alleles of two polymorphisms at positions -238 and -308 in the promoter region of the TNFA gene in a Spanish male population of alcoholics with and without alcoholic liver cirrhosis.

METHODS

149 male alcoholics (84 without alcoholic liver disease, and 65 with alcoholic liver cirrhosis) and 90 control subjects were included. Genotyping was done by polymerase chain reaction and digestion with restriction enzymes.

RESULTS

No significant differences in the distribution of genotypes and alleles of the -308 TNFA gene polymorphism were observed between alcoholics and non-alcoholics, or between alcoholics with liver cirrhosis and those without liver disease. However, we found an association between the -238 TNFA polymorphism and alcoholic liver cirrhosis; the frequency of the heterozygous genotype being significantly higher in alcoholics with cirrhosis than in those without liver damage.

CONCLUSION

The -238 TNFA-A allele is associated with a higher risk to develop alcoholic liver cirrhosis. This polymorphism could be considered as a genetic factors that confer predisposition to suffer liver cirrhosis in the alcoholic population of Castile and León.

Transcription Factor IIA tau is associated with undifferentiated cells and its gene expression is repressed in primary neurons at the chromatin level in vivo

The levels of General Transcription Factor (TF) IIA were examined during mammalian brain development and in rat embryo fibroblasts and transformed cell lines. The large TFIIA subunit paralogues alphabeta and tau are largely produced in unsynchronized cell lines, yet only TFIIA alphabeta is observed in a number of differentiated tissue extracts. Steady-state protein levels of the TFIIA tau, alphabeta, and gamma subunits were significantly reduced when human embryonal (ec) and hepatic carcinoma cell lines were stimulated to differentiate with either all-trans-retinoic acid (ATRA) or sodium butyrate. ATRA-treated NT2-ec cells required replating to induce a neuronal phenotype and loss of detectable TFIIA tau and gamma proteins. High levels of TFIIA tau, alphabeta, and gamma and Sp factors were identified in extracts from human fetal and rat embryonic day-18 brains, but not in human and rat adult brain extracts. A high histone H3 Lys9/Lys4 methylation ratio was observed in the TFIIA tau promoter of primary hippocampal neurons from day-18 rat embryos, suggesting that repressive epigenetic marks of chromatin prevent TFIIA tau from being transcribed in neurons. We conclude that TFIIA tau is associated with undifferentiated cells during development, yet is down-regulated at the chromatin level upon cellular differentiation.

The role of genetic polymorphisms in alcoholic liver disease

Chronic alcohol consumption is a major cause of liver cirrhosis which, however, develops in only a minority of heavy drinkers. Evidence from twin studies indicates that genetic factors account for at least 50% of individual susceptibility. The contribution of genetic factors to the development of diseases may be investigated either by means of animal experiments, through linkage studies in families of affected patients, or population based case-control studies. With regard to the latter, single nucleotide polymorphisms of genes involved in the degradation of alcohol, antioxidant defense, necroinflammation, and formation and degradation of extracellular matrix are attractive candidates for studying genotype-phenotype associations. However, many associations in early studies were found to be spurious and could not be confirmed in stringently designed investigations. Therefore, future genotype-phenotype studies in alcoholic liver disease should meet certain requirements in order to avoid pure chance observations due to a lack of power, false functional interpretation, and insufficient statistical evaluation.

The -159C/T polymorphism in the promoter region of the CD14 gene is associated with advanced liver disease and higher serum levels of acute-phase proteins in heavy drinkers

BACKGROUND

Innate inflammatory responses to endotoxin (lipopolysaccharide) contribute to the development of alcoholic liver disease (ALD). A single-nucleotide polymorphism (-159C/T) in the promoter region of the gene coding for CD14 (a lipopolysaccharide receptor) could be associated with the development of ALD. We sought too investigate the relationship between the CD14/-159C/T polymorphism and advanced ALD and acute-phase protein levels in heavy drinkers.

METHODS

A total of 138 heavy drinkers consecutively admitted to an Internal Medicine department were genotyped for the CD14/-159C/T polymorphism. Serum samples were analyzed for lipopolysaccharide-binding protein (LBP), soluble CD14 (sCD14), C-reactive protein (CRP), and immunoglobulin (Ig) A, IgG, and IgM. Patients with ascites or liver encephalopathy (n = 35) were classified as having advanced ALD.

RESULTS

After adjusting for potential confounding variables, the CD14/-159TT genotype was positively associated with advanced ALD (odds ratio, 2.99; 95% confidence interval, 1.09-8.24, p = 0.03) and serum LBP (p = 0.01) and sCD14 (p = 0.04) levels. The CD14/-159C/T polymorphism was not associated with serum levels of CRP, IgA, IgG, or IgM.

CONCLUSIONS

Our results support the notion that CD14/-159TT homozygous heavy drinkers have higher levels of the LPS-binding acute-phase proteins (LBP and sCD14) than do carriers of the CD14/-159C allele. Also, the CD14/-159TT genotype may be a risk factor for advanced ALD.

Cytochrome P450 2E1 high activity polymorphism in alcohol abuse and end-organ disease

AIM

To investigate a possible role for a recently identified polymorphism in the gene of cytochrome P450 2E1, the presence of which is associated with high activity of the enzyme.

METHODS

Two hundred and thirty-nine alcohol consumers, ICD 10.1/.2 (ALC), and 208 normal controls were studied. PCR amplification of the CYP2E1 gene region was performed to assess polymorphic variation. Fisher's exact test was used to assess the data.

RESULTS

Twelve normal controls (5.8%) possessed the insertion. Five ALC (2.1%) had the insertion; of these 2 of 144 with alcohol induced chronic pancreatitis, none of 28 with alcoholic liver disease and 3 of 67 without end-organ disease had the polymorphism. A significantly Lower frequency of subjects possessed the insertion than normal controls [P=0.049 (genotype analysis P=0.03)]. To further assess, if there was a relationship to alcohol problems per se or end-organ disease, we compared patients with alcohol induced end-organ disease vs alcoholic controls without end-organ disease vs normal controls which again showed a significant difference [P=0.045 (genotype analysis, P=0.011)], further sub-group analysis did not identify which group(s) accounted for these differences.

CONCLUSION

We have shown the frequencies of this high-activity polymorphism in alcohol related patient groups for the first time. The frequency is significantly less in alcoholics than normal controls, as with high activity polymorphisms of alcohol dehydrogenase. The biological significance, and whether the relevance is solely for alcoholism or is there a relationship to end-organ disease, would benefit from the assessment in the populations with a greater frequency of this polymorphism.

CD14 promoter polymorphism in Chinese alcoholic patients with cirrhosis of liver and acute pancreatitis

AIM: To investigate the relationship between genetic polymorphism of the CD14 promoter and the occurrence of alcoholic cirrhosis and alcoholic pancreatitis, and to challenge the conclusion made earlier that the patients with acute alcoholic pancreatitis and patients with alcoholic cirrhosis of liver are two different subpopulations.

METHODS: Using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, we determined the polymorphism of CD14 gene and aldehyde dehydrogenase gene 2 (ALDH 2) in 335 alcoholic patients with different organ complications i.e., cirrhosis of liver (n = 100), acute pancreatitis (n = 100), esophageal cancer (n = 82) and avascular necrosis of hip joint (AVN) (n = 53) and 194 non-alcoholic controls in a Chinese group.

RESULTS: The results showed that the carriage of T allele was not different among alcoholic patients with cirrhosis of liver, alcoholic patients with other complication and non-alcoholic controls. On the other hand, the carriage of the C allele was significantly more prevalent for alcoholic pancreatitis than for esophageal cancer (0.79 vs 0.60, P<0.001), alcoholic AVN (0.79vs 0.65, P<0.025) and non-alcoholic controls (0.79 vs 0.68, P<0.025). Furthermore, when only subjects with ALDH2 1-1 genotype were examined, the C allele frequency was significantly more prevalent for alcoholic pancreatitis than for alcoholic liver cirrhosis (0.82 vs 0.69, P<0.025), esophageal cancer (0.82 vs 0.61, P<0.01), alcoholic AVN (0.82 vs 0.64, P<0.01) and non-alcoholic controls (0.82 vs 0.69, P<0.05).

CONCLUSION: The C allele may be associated with some mechanism, which is important in the pathogenesis of alcoholic pancreatitis, and that alcoholic patients with acute pancreatitis and cirrhosis of liver are probably two different subpopulations.

INTERLEUKIN-1 GENE CLUSTER POLYMORPHISMS AND ALCOHOLISM IN SPANISH MEN

AIMS

In an attempt to explain differences in susceptibility to alcoholism and alcohol liver disease (ALD), different genes have been analysed, among them those encoding inflammatory cytokines. Thus, it has been reported recently that both the interleukin 1 receptor antagonist (IL1RN) and the IL1beta (IL1B) genes may influence the risk of ALD in Japanese alcoholics. We analysed the distribution of single nucleotide polymorphisms (SNPs) located in the IL1A, IL1B, IL1R1 and IL1RN genes in alcoholic and non-alcoholic Spanish subjects.

METHODS

DNA samples were obtained from 139 male alcoholics, 78 of whom were diagnosed as alcohol dependent (32 patients with liver cirrhosis and 46 without ALD) and 61 as alcohol abusers (25 with liver cirrhosis and 36 without ALD). As a control, we studied 81 age- and sex-matched healthy volunteers.

RESULTS

Alleles -511 IL1B*1 and IL1RN*1 were represented more in alcoholic patients than in the control group. We did not find any association of alcoholism or ALD with polymorphisms in the IL1A and IL1R1 genes.

CONCLUSIONS

We conclude that the proteins encoded by the IL1RN and IL1B genes may be involved in susceptibility to alcoholism in Spanish men, probably through a different pathway from that involved in the regulation of the inflammatory response.

Metabolism of alcohol

Most tissues of the body contain enzymes capable of ethanol oxidation or nonoxidative metabolism, but significant activity occurs only in the liver and, to a lesser extent, in the stomach. Hence, medical consequences are predominant in these organs. In the liver, ethanol oxidation generates an excess of reducing equivalents, primarily as NADH, causing hepatotoxicity. An additional system, containing cytochromes P-450 inducible by chronic alcohol feeding, was demonstrated in liver microsomes and found to be a major cause of hepatotoxicity.

Genetic polymorphisms influencing xenobiotic metabolism and transport in patients with primary biliary cirrhosis

Epidemiological data suggest that environmental factors may trigger autoimmunity in genetically susceptible individuals. In primary biliary cirrhosis (PBC), it has been postulated that halogenated xenobiotics can modify self-molecules, facilitating the breakdown of tolerance to mitochondrial antigens. The transport and metabolism of xenobiotics is highly dependent on key genetic polymorphisms that alter enzymatic phenotype. We analyzed genomic DNA from 169 patients with PBC and 225 geographically and sex-matched healthy subjects for polymorphisms of genes coding for cytochromes P450 (CYPs) 2D6 (CYP2D6*4, CYP2D6*3, CYP2D6*5, and CYP2D6*6) and 2E1 (cl/c2), multidrug resistance 1 (MDR1 C3435T) P-glycoprotein, and pregnane X receptor (PXR C-25385T, C8055T, and A7635G). We compared the genotype frequencies in patients and controls and also correlated polymorphisms with PBC severity. The distributions of the studied genotypes did not significantly differ between patients and controls. However, when clinical characteristics of patients with PBC were compared according to genotype, the CYP2E1 c2 allele was associated with signs of more severe disease. In conclusion, genetic polymorphisms of CYP 2D6 and 2E1, PXR, and MDR1 do not appear to play a role in the onset of PBC.

Genetic polymorphisms of ADH2, ADH3, CYP4502E1 Dra-I and Pst-I, and ALDH2 in Spanish men: lack of association with alcoholism and alcoholic liver disease

BACKGROUND/AIMS

The relationship between polymorphisms at the alcohol dehydrogenase 2 (ADH(2)), ADH(3), CYP(450)2E1 and aldehyde dehydrogenase 2 (ALDH(2)) loci and the individual predisposition to alcoholism and alcoholic liver disease in Caucasians is controversial.

METHODS

We determined the genotypes of ADH(2), ADH(3), CYP(450)2E1 (Pst-I and Dra-I) and ALDH(2) in 519 male Spaniards: 264 alcoholic subjects (47 without liver disease, 118 with non-cirrhotic liver disease and 99 with cirrhosis) and 255 non-alcoholic subjects (64 healthy controls, 110 with non-cirrhotic non-alcoholic liver disease and 81 with cirrhosis unrelated to alcohol). Genotyping was performed using PCR-RFLP methods on white cell DNA.

RESULTS

The distribution of the allelic variants (allele *1 and allele *2) in the whole subjects analyzed was: ADH(2) 93.1% and 6.9%; ADH(3) 55.7 and 44.3%; CYP(450)2E1 Dra-I 11.2 and 88.8%; CYP(450)2E1 Pst-I 96.2 and 3.8% and ALDH2 100 and 0%, respectively. No differences were observed in the allelic distributions of the alcoholic and non-alcoholic subjects for the loci examined. Allele distribution in alcoholics with no liver disease, with alcoholic steatosis or hepatitis, and with cirrhosis was also similar.

CONCLUSIONS

ADH(2), ADH(3), and CYP(450)2E1 Pst-I and Dra-I genetic variations are not related to alcoholism or susceptibility to alcoholic liver disease in our male population. ALDH(2) locus is monomorphic.

Expression of cytochrome P4502E1 gene in hepatocellular carcinoma

AIM: To investigate cytpchrome P4502E1 (CYP2E1) gene expression in occurrence and progression of hepatocellular carcinoma (HCC).

METHODS: The human liver arrayed library was spotted onto the nylon membranes to make cDNA array. Hybridization of cDNA array was performed with labeled probes synthesized from RNA isolated from HCC and adjacent liver tissues. Sprague-Dawley rats were administrated diethylnitrosamine (DENA) to induce HCC. CYP2E1 expression was detected by the method of RT-PCR and Northern blot analysis.

RESULTS: CYP2E1 was found by cDNA array hybridization to express differently between HCC and liver tissues. CYP2E1 only expressed in liver, but did not express in HCC tissues and expressed lowly in cirrhotic tissues. In the progression of cirrhosis and HCC, the expression level of CYP2E1 was gradually decreased and hardly detected until the late stage of HCC.

CONCLUSION: Using arrayed library to make cDNA arrays is an effective method to find differential expression genes. CYP2E1 is a unique gene expressing in liver but did not express in HCC. CYP2E1 expression descended along with the initiation and progression of HCC, which is noteworthy further investigations in its significance in the development of HCC.

Genetic polymorphism in ethanol metabolism: acetaldehyde contribution to alcohol abuse and alcoholism

Acetaldehyde, the first product of ethanol metabolism, has been speculated to be involved in many pharmacological and behavioral effects of ethanol. In particular, acetaldehyde has been suggested to contribute to alcohol abuse and alcoholism. In the present paper, we review current data on the role of acetaldehyde and ethanol metabolism in alcohol consumption and abuse. Ethanol metabolism involves several enzymes. Whereas alcohol dehydrogenase metabolizes the bulk of ethanol within the liver, other enzymes, such as cytochrome P4502E1 and catalase, also contributes to the production of acetaldehyde from ethanol oxidation. In turn, acetaldehyde is metabolized by the enzyme aldehyde dehydrogenase. In animal studies, acetaldehyde is mainly reinforcing particularly when injected directly into the brain. In humans, genetic polymorphisms of the enzymes alcohol dehydrogenase and aldehyde dehydrogenase are also associated with alcohol drinking habits and the incidence of alcohol abuse. From these human genetic studies, it has been concluded that blood acetaldehyde accumulation induces unpleasant effects that prevent further alcohol drinking. It is therefore speculated that acetaldehyde exerts opposite hedonic effects depending on the localization of its accumulation. In the periphery, acetaldehyde is primarily aversive, whereas brain acetaldehyde is mainly reinforcing. However, the peripheral effects of acetaldehyde might also be dependent upon its peak blood concentrations and its rate of accumulation, with a narrow range of blood acetaldehyde concentrations being reinforcing.

Investigation of alcohol metabolizing enzyme genes in Chinese alcoholics with avascular necrosis of hip joint, pancreatitis and cirrhosis of the liver

AIMS AND METHODS

Alcoholism may cause a range of diseases including avascular necrosis of the hip joint (AVN), cirrhosis of the liver, pancreatitis and oesophageal carcinoma. Chinese alcoholic patients diagnosed with AVN have a higher incidence of cirrhosis than of acute pancreatitis or oesophageal cancer. Thus, the aim of this study was to investigate genetic differences in polymorphisms of the alcohol-metabolizing enzymes ADH2, ADH3, ALDH2 and P4502E1 for subgroups of Chinese alcoholic patients, defined by diagnoses of AVN (n = 51), acute pancreatitis (n = 92) and liver cirrhosis (n = 159), and for 280 non-alcoholic patients.

RESULTS

Analysis revealed that ADH2*1 allele frequency was significantly lower for the alcoholic AVN than for the cirrhosis subgroup. However, no significant difference was found between the alcoholic AVN and pancreatitis subgroups. Furthermore, ALDH2*2 prevalence was not found to differ significantly between the alcoholic subgroups. When compared with our previously published data for alcoholic patients with oesophageal carcinoma, ADH2*1 carriage was significantly less frequent for the alcoholic AVN patients in the current study. Further, ALDH2*2 carriage was significantly less frequent for the alcoholic AVN subgroup than for the oesophageal carcinoma patients.

CONCLUSIONS

The allele frequencies for ADH2*1 and ALDH2*2 are different when comparing subpopulations of alcoholics defined by presence of specific alcohol-induced diseases, suggesting that genetic variation in alcohol-metabolizing enzyme genes accounts for, at least in part, the specific types of organ damage observed. We also found the combination of AVN and cirrhosis to be more prevalent than that of AVN and acute pancreatitis. In contrast, the ADH2 and ALDH2 allele frequencies for the AVN subgroup were more similar to those of the acute-pancreatitis than to the cirrhosis subgroup. These data indicate the possibility that other genetic variations may also influence the type of organ-specific complications in Chinese alcoholics.

Genotyping of cytochrome P450 isoform genes is useful for forensic identification of cadaver

Tailor-made medical treatment based on the polymorphism of genes encoding drug-metabolizing enzymes has been advocated and is being tried on an experimental basis at numerous centers. If DNA polymorphism analysis becomes routine in tailor-made medical treatment, it will be very useful in forensic identification. In this study, we determined the genotype frequencies of five p450 (CYP) isoform genes, CYP1A2, CYP2D6, CYP2E1, CYP2C9 and CYP2C19 in 196 Japanese individuals to evaluate their forensic usefulness. These genes encode the most important enzymes among the CYP superfamily that metabolize clinically used drug. The frequency of each allele agreed well with those reported previously and their genotype frequencies did not deviate from those expected from Hardy-Weinberg equilibrium. CYP2C subfamilies such as CYP2C9 and CYP2C19 on chromosome 10 showed high sequence homology, as high as over 95% in the regions flanking polymorphic sites. Although 3240 genotype combinations of these five CYP isoform genes are theoretically possible, 101 combinations were detected in this study. The genotype frequencies of these five isoform genes excluded their linkage. The following two genotype combinations showed the highest frequency of 0.036: CYP1A2*1A/*1A, CYP2D6*1/*10, CYP2E1*1/*1, CYP2C9*1/*1 and CYP2C19*1/*1 and CYP1A2*1A/*1C, CYP2D6*1/*10, CYP2E1*1/*1, CYP2C9*1/*1 and CYP2C19*1/*1. Thus, genotyping of CYP isoform genes should be useful in forensic identification.

Central role of PPARalpha-dependent hepatic lipid turnover in dietary steatohepatitis in mice

We have proposed that steatohepatitis results from reactive oxygen species (ROS) acting on accumulated fatty acids to form proinflammatory lipoperoxides. Cytochrome P450 4a (Cyp4a) and Cyp2e1 are potential hepatic sources of ROS. We tested the hypothesis that increasing Cyp4a through activation of peroxisome proliferator-activated receptor alpha (PPARalpha) should aggravate steatohepatitis produced by feeding a methionine and choline deficient (MCD) diet. Conversely, we assessed dietary steatohepatitis in PPARalpha(-/-) mice that cannot up-regulate Cyp4a. Male wild type (wt) or PPARalpha(-/-) mice (C57BL6 background) were fed the MCD diet with or without Wy-14,643 (0.1% wt/wt), a potent PPARalpha agonist. Controls were fed the same diet supplemented with methionine and choline. After 5 weeks, wt mice fed the MCD diet developed moderate steatohepatitis and alanine aminotransferase (ALT) levels were increased. Wy-14,643 prevented rather than increased liver injury; ALT levels were only mildly elevated whereas steatohepatitis was absent. Wy-14,643 up-regulated mRNA for liver fatty acid binding protein and peroxisomal beta-oxidation enzymes (acyl-CoA oxidase, bifunctional enzyme, and ketothiolase), thereby reducing hepatic triglycerides and preventing steatosis. In wt mice, dietary feeding up-regulated Cyp4a14 mRNA 2.7-fold and increased hepatic lipoperoxides compared with controls. Wy-14,643 prevented hepatic lipoperoxides from accumulating despite an 18-fold increase in both Cyp4a10 and Cyp4a14 mRNA. PPARalpha(-/-) mice fed the MCD diet developed more severe steatohepatitis than wt mice, and were unaffected by Wy-14,643. In conclusion, PPARalpha activation both increases Cyp4a expression and enhances hepatic lipid turnover; the latter effect removes fatty acids as substrate for lipid peroxidation and is sufficiently powerful to prevent the development of dietary steatohepatitis.

Genetic polymorphisms of tobacco- and alcohol-related metabolizing enzymes and the risk of hepatocellular carcinoma

The effect of genetic polymorphisms for glutathione S-transferase ( GST) M1, GSTT1, GSTP1-1( GSTP1), cytochrome P450 2E1 ( CYP2E1) and aldehyde dehydrogenase 2 ( ALDH2) on the risk of hepatocellular carcinoma (HCC) was observed in 78 Japanese patients with HCC and 138 non-cancer hospital controls. We found a positive association between cumulative amounts of alcohol consumption (>/=600,000 ml in a lifetime) and the risk of HCC (OR=4.52, 95% CI 2.39-8.55). However, cigarette smoking was not significantly related to the risk of HCC (OR=1.23, 95% CI 0.57-2.68). The allelic frequencies of GSTM1, GSTT1, GSTP1, CYP2E1and ALDH2of HCC patients were not significantly different from those of controls when odds ratios were only adjusted for age and gender except for any 2 alleles of ALDH2in drinkers (OR=2.53, 95% CI 1.21-5.31). However, the frequency of any C2 alleles of CYP2E1and any 2 alleles of ALDH2were significantly higher than those of controls (OR=5.77, 95% CI 1.24-27.39, OR=9.77, 95% CI 1.63-58.60) when covariates including viremia were selected by using stepwise logistic regression analysis. We conclude that habitual alcohol drinking is likely to lead to an increased risk of HCC, and any C2alleles of CYP2E1as well as any two alleles of ALDH2were also associated with an increased risk of HCC.

CYP enzyme polymorphisms and susceptibility to HCV-related chronic liver disease and liver cancer

Cancer risk can be influenced by the exposure to endogenous or environmental toxins. Polymorphic enzymes involved in the metabolic activation/detoxification of carcinogens may account for individual variations of risk. We studied the polymorphisms of five enzymes of the P450 superfamily, CYP1A1, CYP1A2, CYP2D6, CYP2E1 and CY3A4, as risk factors for liver disease progression and cancer in hepatitis C virus-infected patients. CYP genotyping was performed by polymerase chain reaction (PCR) restriction fragment length polymorphism or allele-specific PCR. Different stages of disease were considered, as follows: 90 asymptomatic carriers and 87 chronic hepatitis, 92 cirrhosis and 91 hepatocellular carcinoma (HCC) cases. Reference allele frequencies were obtained from 99 blood donors. Allele distributions among categories were compared using the chi(2) test. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to express relative risks. Independent associations were modeled by correspondence analysis and logistic regression. Frequencies of the CYP1A1 highly inducible alleles, MspI m2 and Val, were increased in liver disease patients compared with carriers; no specific association with HCC was found. The high-activity CYP2E1 c2 allele was underrepresented among HCC patients with respect to other HCV categories, including cirrhosis. CYP2D6 poor metabolizer (PM) genotypes were significantly more frequent in healthy subjects (7.1%) and carriers (11.1%) than in hepatitis/cirrhosis (4.6%) and HCC (1.2%) patients. This was confirmed by multivariable analysis. PM genotypes protected against progressive disease as ORs reduced proportionally to stage. The age at diagnosis for HCC was anticipated in non-PM individuals. No differences were seen for CYP1A2 and CYP3A4 genes. Polymorphic variants of CYP genes may contribute to the progression of liver disease and HCC risk in HCV-infected subjects.

Cytochrome P450 2E1 genotype and the susceptibility to antituberculosis drug-induced hepatitis

Most cases with antituberculosis drug-induced hepatitis have been attributed to isoniazid. Isoniazid is metabolized by hepatic N-acetyltransferase (NAT) and cytochrome P450 2E1 (CYP2E1) to form hepatotoxins. However, the role of CYP2E1 in this hepatotoxicity has not yet been reported. The aim of this study was to evaluate whether the polymorphism of the CYP2E1 gene is associated with antituberculosis drug-induced hepatitis. A total of 318 tuberculosis patients who received antituberculosis treatment were followed prospectively. Their CYP2E1 and NAT2 genotypes were determined using a polymerase chain reaction with restriction fragment length polymorphism method. Twenty-one healthy volunteers were recruited for CYP2E1 phenotype study using a chlorzoxazone test. Forty-nine (15.4%) patients were diagnosed to have drug-induced hepatotoxicity. Patients with homozygous wild genotype CYP2E1 c1/c1 had a higher risk of hepatotoxicity (20.0%; odds ratio [OR], 2.52) than those with mutant allele c2 (CYP2E1 c1/c2 or c2/c2, 9.0%, P =.009). If CYP2E1 c1/c2 or c2/c2 genotype combined with rapid acetylator status was regarded as the reference group, the risk of hepatotoxicity increased from 3.94 for CYP2E1 c1/c1 with rapid acetylator status to 7.43 for CYP2E1 c1/c1 with slow acetylator status. After adjustment for acetylator status and age, the CYP2E1 c1/c1 genotype remained an independent risk factor for hepatotoxicity (OR, 2.38; P =.017). Furthermore, under the administration of isoniazid, the volunteers with CYP2E1 c1/c1 genotype had higher CYP2E1 activity than those with other genotypes had and, hence, might produce more hepatotoxins. In conclusion, CYP 2E1 genetic polymorphism may be associated with susceptibility to antituberculosis drug-induced hepatitis.

Genetic differences in ethanol metabolizing enzymes and blood pressure in Japanese alcohol consumers

Orientals have unique genetic polymorphisms in ethanol metabolizing enzymes, such as alcohol dehydrogenase-2 (ADH2), aldehyde dehydrogenase-2 (ALDH2) and cytochrome P450-2E1 (CYP2E1). Of the three studies conducted to clarify the influence of ALDH2 genotypes on sensitivity to the pressor effects of alcohol in Japanese, only one was suggested, though indirectly, higher sensitivity in drinkers having the genotype of inactive ALDH2. This discrepancy prompted us to determine ADH2, ALDH2 and CYP2E1 genotypes in the genomic DNA extracted from white blood cells of 855 healthy middle-aged Japanese men, and to analyse the associations with the alcohol-blood pressure (BP) relationship. No marked differences were found in the relationship among the genotypes of ALDH2, although the subjects with intact ALDH2 showed a slightly higher BP than those with inactive ALDH2 probably due to under-reporting of alcohol consumption in those with intact ALDH2 who could thus drink more. No significant influence of ADH2 genotypes was observed. A higher BP was noted in large volume alcohol consumers having c2/c2 genotype of CYP2E1. Multivariate regression analysis adjusting for the effects of age, body mass index and the volume of alcohol consumed, all of which are strong determinants of BP levels, showed only a marginal effect of c2 allele of CYP2E1 on diastolic BP elevations with increases in alcohol consumption. Thus it is concluded that the genetic polymorphisms in ethanol-metabolizing enzymes do not greatly influence the alcohol-BP relationship in Japanese men.

Acetaminophen hepatotoxicity: the first 35 years

The acetaminophen nomogram including its uses and limitations is discussed as well as the development of the N-acetylcysteine protocol. While it has taken many years to elucidate the genetic variability and true multiplicity of the cytochrome P450 "mixed function oxidase system" many publications early on looked at the enzyme system as a single entity. Numerous articles indicated that barbiturates, anticonvulsants, and others could induce "P450" and add to the toxicity of acetaminophen. It rapidly became apparent that just because "P450" was induced when measured as a whole, not all other substrates would have changed metabolic activity. The role of diet and ethanol induction and inhibition on CYP2E1, the enzyme of greatest interest for acetaminophen is multifaceted. The lack of enhancement of acetaminophen toxicity by phenytoin and in fact, the potential for reduction of toxicity with that agent is a good example of the evolution of our knowledge. Further complicating our understanding is the introduction of misleading terms such as "therapeutic misadventure" and other expressions of molecular intent. A critical understanding of the literature makes it clear that therapeutic doses of acetaminophen either alone or in the presence of inducers do not produce toxicity. While the community of clinical toxicologists is small, it needs to be more aggressive in making sure that physicians from other specialties and non-clinical toxicology colleagues understand the significance and implications of this science.

Childhood acute lymphoblastic leukemia associated with parental alcohol consumption and polymorphisms of carcinogen-metabolizing genes

BACKGROUND

Limited information is available on the association of parental consumption of alcohol prior to and during pregnancy with the risk of childhood leukemia, as well as for the potentially modifying role of genetic polymorphisms.

METHODS

We conducted a population-based, case-control study of 491 incident cases of acute lymphoblastic leukemia age 0-9 years and matched on age and sex to 491 healthy controls. Cases were identified at tertiary care centers in the Province of Québec between 1980 and 1993. Each parent was interviewed separately about alcohol consumption habits. We also used a case-only design with 186 cases to estimate interaction odds ratios between prenatal exposure and child DNA variants in the GSTM1 and CYP2E1 genes.

RESULTS

The adjusted odds ratio for any maternal consumption during pregnancy was 0.7 (95% confidence interval = 0.5-0.9). The interaction odds ratios for the GSTM1 null genotype during third pregnancy trimester was 2.4 (95% confidence interval = 1.1-5.4); the interaction odds ratio for CYP2E1 variant G-1295C (or allele *5) during the nursing period was 4.9 (95% confidence interval = 1.5-16.7).

CONCLUSIONS

The observed association with maternal alcohol consumption during pregnancy could be due to the potential chemopreventive effects of flavonoids found in wine and beer. These possible effects of alcohol may be at least partially genetically determined, although data are preliminary.

Polymorphism in alcohol-metabolizing enzymes, glutathione S-transferases and apolipoprotein E and susceptibility to alcohol-induced cirrhosis and chronic pancreatitis

BACKGROUND AND AIM

Susceptibility to organ damage induced by alcohol may be due to inherited variation (polymorphism) in ethanol-metabolizing enzymes, or to polymorphisms affecting free radical or lipid metabolism mediated by enzymes such as glutathione S-transferases and apolipoprotein E. The aim was to compare the genotype frequencies of alcohol dehydrogenase-2 (ADH2), ADH3, aldehyde dehydrogenase-2 (ALDH2), cytochrome P450-2E1 (CYP2E1), glutathione S-transferase-M1 (GSTM1), GSTT1, and apolipoprotein E in patients with alcoholic cirrhosis and alcoholic chronic pancreatitis to those in control groups.

PATIENTS AND METHODS

The case-control study was restricted to Caucasian adults: 57 with alcoholic cirrhosis, 71 with alcoholic chronic pancreatitis, 57 alcoholics without apparent organ damage and 200 healthy blood donors. Genotypes were determined by restriction fragment length polymorphism after amplification of genomic DNA by polymerase chain reaction.

RESULTS

The genotype ADH3*2/*2 was more frequent in patients with cirrhosis (40%) than blood donors (12%; OR 4.92, 95% CI 2.36-10.31) and patients with chronic pancreatitis (8%; OR 7.33, 95% CI 2.54-23.78) but was not significantly different from alcoholic controls (23%; OR 2.27, 95% CI 0.95-5.66). Patients with cirrhosis also had a higher frequency (P < 0.05) of ADH2*1/*1 (100%) than blood donors (92%) and those with chronic pancreatitis (93%). The frequencies of genotypes of ALDH2, CYP2E1, GSTM1, GSTT1 and apolipoprotein E were similar in all groups.

CONCLUSION

Alcoholic cirrhosis but not alcoholic chronic pancreatitis is associated with ADH3*2/*2 and perhaps with ADH2*1/*1. Both genes encode less active alcohol-metabolizing enzymes that may be associated with cirrhosis because of delayed formation of acetaldehyde (with higher intakes of alcohol), or diversion of alcohol metabolism through pathways other than ADH.