Increased serum anti-CYP2E1 IgG autoantibody levels may be involved in the pathogenesis of occupational trichloroethylene hypersensitivity syndrome: a case-control study.

Occupational exposure to trichloroethylene (TCE) causes a systemic skin disorder with hepatitis known as TCE hypersensitivity syndrome (TCE-HS). Human Leukocyte Antigen (HLA)-B*13:01 is its susceptibility factor; however, the immunological pathogenesis of TCE-HS remains unknown. We herein examined the hypothesis that autoantibodies to CYP2E1 are primarily involved in TCE-HS. A case-control study of 80 TCE-HS patients, 186 TCE-tolerant controls (TCE-TC), and 71 TCE-nonexposed controls (TCE-nonEC) was conducted to measure their serum anti-CYP2E1 antibody (IgG) levels. The effects of TCE exposure indices, such as 8-h time-weighted-average (TWA) airborne concentrations, urinary metabolite concentrations, and TCE usage duration; sex; smoking and drinking habits; and alanine aminotransferase (ALT) levels on the antibody levels were also analyzed in the two control groups. There were significant differences in anti-CYP2E1 antibody levels among the three groups: TCE-TC > TCE-HS patients > TCE-nonEC. Antibody levels were not different between HLA-B*13:01 carriers and noncarriers in TCE-HS patients and TCE-TC. The serum CYP2E1 measurement suggested increased immunocomplex levels only in patients with TCE-HS. Multiple regression analysis for the two control groups showed that the antibody levels were significantly higher by the TCE exposure. Women had higher antibody levels than men; however, smoking, drinking, and ALT levels did not affect the anti-CYP2E1 antibody levels. Anti-CYP2E1 antibodies were elevated at concentrations lower than the TWA concentration of 2.5 ppm for TCE exposure. Since HLA-B*13:01 polymorphism was not involved in the autoantibody levels, the possible mechanism underlying the pathogenesis of TCE-HS is that TCE exposure induces anti-CYP2E1 autoantibody production, and HLA-B*13:01 is involved in the development of TCE-HS.

Serum derived from ulcerative colitis mouse changes the metabolism of the fluorescent substrate by P450 depending on the degree of disease progression.

Ulcerative colitis (UC) is characterized by erosions of the intestinal mucosa. The number of patients with UC has recently been increasing rapidly. Since the diagnosis of UC is complex and difficult, a simple, rapid, noninvasive technique for diagnosing UC is needed urgently. The expression of cytochrome P450 (P450 or CYP) species in mouse liver is known to be changed dependent on the disease. Various components such as P450 substrates and P450 metabolites in the blood may possibly change with the UC-specific way in mouse. In this study, in order to evaluate UC-specific components in UC mouse serum, we analyzed the influence of serum derived from UC mice on the results of fluorescent P450 inhibition assays based on 12 human P450 enzymes, such as CYP1A1, CYP2C8, CYP2E1,CYP3A4, CYP1A2, CYP2D6, CYP2A13, CYP2B6, CYP2C9, CYP2C18, CYP2C19, and CYP3A5. At first, in order to induce UC, mice received 4,4-dimethyl-4-silapentane-1-sulfonic acid (DSS) dissolved in their drinking water for 7 days. Next, these 12 human P450 enzymes were expressed in E. coli cells. Then, P450 fluorescent competition reaction was performed using these P450 enzymes and serum of UC mice. We found that the metabolism of fluorescent substrates by CYP2B6, CYP2C19, CYP2E1, and CYP1A1 in the presence of serum obtained from DSS-treated mice was activated by 42%, 37%, 37%, and 23%, respectively, relative to that associated with sera from control mice. A receiver operating characteristic (ROC) curve analysis was carried out with the 31 samples of UC mice and healthy mice. Area under the ROC curve (AUC) value was calculated from ROC curve. AUC value of CYP2E1 and CYP2C19 showed 0.921 and 0.892, respectively. Therefore, it was shown that CYP2C19 and CYP2E1 could be used as biomarkers for evaluating ulcerative colitis. From these results, it is suggested that these simple fluorescent P450 inhibition assays have potential as a new diagnostic procedure for UC in mouse. This study is the first report on a simple non-invasive method for evaluating UC using P450 enzyme and serum interaction.

Hypomethylation of CYP2E1 and DUSP22 Promoters Associated With Disease Activity and Erosive Disease Among Rheumatoid Arthritis Patients.

OBJECTIVE: Epigenetic modifications have previously been associated with rheumatoid arthritis (RA). In this study, we aimed to determine whether differential DNA methylation in peripheral blood cell subpopulations is associated with any of 4 clinical outcomes among RA patients. METHODS: Peripheral blood samples were obtained from 63 patients in the University of California, San Francisco RA cohort (all satisfied the American College of Rheumatology classification criteria; 57 were seropositive for rheumatoid factor and/or anti-cyclic citrullinated protein). Fluorescence-activated cell sorting was used to separate the cells into 4 immune cell subpopulations (CD14+ monocytes, CD19+ B cells, CD4+ naive T cells, and CD4+ memory T cells) per individual, and 229 epigenome-wide DNA methylation profiles were generated using Illumina HumanMethylation450 BeadChips. Differentially methylated positions and regions associated with the Clinical Disease Activity Index score, erosive disease, RA Articular Damage score, Sharp score, medication at time of blood draw, smoking status, and disease duration were identified using robust regression models and empirical Bayes variance estimators. RESULTS: Differential methylation of CpG sites associated with clinical outcomes was observed in all 4 cell types. Hypomethylated regions in the CYP2E1 and DUSP22 gene promoters were associated with active and erosive disease, respectively. Pathway analyses suggested that the biologic mechanisms underlying each clinical outcome are cell type-specific. Evidence of independent effects on DNA methylation from smoking, medication use, and disease duration were also identified. CONCLUSION: Methylation signatures specific to RA clinical outcomes may have utility as biomarkers or predictors of exposure, disease progression, and disease severity.

Proteomic Characteristics of Blood Serum in Rats with Different Behavioral Parameters after Acute Stress.

We studied proteome profile of blood serum of Wistar rats with different behavioral activity immediately and in 1 and 3 days after acute stress on the model of 12-h immobilization during the nighttime. Comparative analysis of 2D-electrophoretograms revealed differences in the expression of serum proteins in non-stressed (control) and stressed (experimental) rats. We found 22 protein spots that characterized the proteomic features of blood serum in rats with different prognostic resistance to stress. Mass-spectrometry of isolated spots identified 6 functional proteins. Persistent proteome changes in the blood of animals at different stages after acute stress were determined. The specificity of proteomic characteristics of blood serum was shown in behaviorally passive and active rats during the post-stress period. These data extend the concept on specific protein markers for the formation of a negative emotional state and adaptive-and-compensatory processes in mammals with different sensitivity to stressogenic factors.

Saikosaponins induced hepatotoxicity in mice via lipid metabolism dysregulation and oxidative stress: a proteomic study.

BACKGROUND: Radix Bupleuri (RB) has been popularly used for treating many liver diseases such as chronic hepatic inflammation and viral Hepatitis in China. Increasing clinical and experimental evidence indicates the potential hepatotoxicity of RB or prescriptions containing RB. Recently, Saikosaponins (SS) have been identified as major bioactive compounds isolated from RB, which may be also responsible for RB-induced liver injury. METHODS: Serum AST, ALT and LDH levels were determined to evaluate SS-induced liver injury in mice. Serum and liver total triglyceride and cholesterol were used to indicate lipid metabolism homeostasis. Liver ROS, GSH, MDA and iNOS were used to examine the oxidative stress level after SS administration. Western blot was used to detect CYP2E1 expression. A 8-Plex iTRAQ Labeling Coupled with 2D LC - MS/MS technique was applied to analyze the protein expression profiles in livers of mice administered with different doses of SS for different time periods. Gene ontology analysis, cluster and enrichment analysis were employed to elucidate potential mechanism involved. HepG2 cells were used to identify our findings in vitro. RESULTS: SS dose- and time-dependently induced liver injury in mice, indicated by increased serum AST, ALT and LDH levels. According to proteomic analysis, 487 differentially expressed proteins were identified in mice administrated with different dose of SS for different time periods. Altered proteins were enriched in pathways such as lipid metabolism, protein metabolism, macro molecular transportation, cytoskeleton structure and response to stress. SS enhanced CYP2E1 expression in a time and dose dependent manner, and induced oxidative stress both in vivo and in vitro. CONCLUSION: Our results identified hepatotoxicity and established dose-time course-liver toxicity relationship in mice model of SS administration and suggested potential mechanisms, including impaired lipid and protein metabolism and oxidative stress. The current study provides experimental evidence for clinical safe use of RB, and also new insights into understanding the mechanism by which SS and RB induced liver injury.

A non-hepatotropic parasite infection increases mortality in the acetaminophen-induced acute liver failure murine model: possible roles for IL-5 and IL-6

We evaluated the effects of a non-hepatotropic parasite infection (Taenia crassiceps) on the outcome of acetaminophen-induced acute liver failure in mice. Uninfected and T. crassiceps infected mice orally received either 300 mg/kg acetaminophen or water as vehicle (n = 5 per group). Survival analysis, hepatocyte necrosis, alanine aminotransferase (ALT) levels, CYP2E1 protein, interleukin (IL-) 5, and IL-6 were assessed for all groups. All infected mice died within 16 h after exposure to acetaminophen (Tc+APAP group), whereas only one-third of uninfected animals exposed to acetaminophen (APAP group) died. Uninfected (Control group) and infected (Tc group) mice that received the vehicle showed no liver damage. Tc+APAP mice exhibited massive liver necrosis characterised by marked balloning degeneration of hepatocytes and higher serum ALT compared to Control, Tc, and APAP animals. Liver tissue from Tc+APAP mice also displayed increased expression of CYP2E1 protein and higher mRNA and protein levels of IL-5 and IL-6 compared to the other groups. These findings suggest that non-hepatotropic parasite infections may increase mortality following acute liver failure by promoting hepatocyte necrosis via IL-5 and IL-6-dependent CYP2E1 overproduction. This study identifies new potential risk factors associated with severe acute liver failure in patients.

A non-hepatotropic parasite infection increases mortality in the acetaminophen-induced acute liver failure murine model: possible roles for IL-5 and IL-6.

We evaluated the effects of a non-hepatotropic parasite infection (Taenia crassiceps) on the outcome of acetaminophen-induced acute liver failure in mice. Uninfected and T. crassiceps infected mice orally received either 300 mg/kg acetaminophen or water as vehicle (n = 5 per group). Survival analysis, hepatocyte necrosis, alanine aminotransferase (ALT) levels, CYP2E1 protein, interleukin (IL-) 5, and IL-6 were assessed for all groups. All infected mice died within 16 h after exposure to acetaminophen (Tc+APAP group), whereas only one-third of uninfected animals exposed to acetaminophen (APAP group) died. Uninfected (Control group) and infected (Tc group) mice that received the vehicle showed no liver damage. Tc+APAP mice exhibited massive liver necrosis characterised by marked balloning degeneration of hepatocytes and higher serum ALT compared to Control, Tc, and APAP animals. Liver tissue from Tc+APAP mice also displayed increased expression of CYP2E1 protein and higher mRNA and protein levels of IL-5 and IL-6 compared to the other groups. These findings suggest that non-hepatotropic parasite infections may increase mortality following acute liver failure by promoting hepatocyte necrosis via IL-5 and IL-6-dependent CYP2E1 overproduction. This study identifies new potential risk factors associated with severe acute liver failure in patients.

Insulin resistance alters hepatic ethanol metabolism: studies in mice and children with non-alcoholic fatty liver disease.

OBJECTIVE: Increased fasting blood ethanol levels, suggested to stem from an increased endogenous ethanol synthesis in the GI tract, are discussed to be critical in the development of non-alcoholic fatty liver disease (NAFLD). The aim of the present study was to further delineate the mechanisms involved in the elevated blood ethanol levels found in patients with NAFLD. DESIGN: In 20 nutritionally and metabolically screened children displaying early signs of NAFLD and 29 controls (aged 5-8 years), ethanol plasma levels were assessed. Ethanol levels along the GI tract, in vena cava and portal vein, intestinal and faecal microbiota, and activity of alcohol dehydrogenase (ADH) and cytochrome P450 2E1 (CYP2E1) were measured in wild-type, ob/ob and anti-TNFα antibody (aT) treated ob/ob mice. RESULTS: Despite not differing in dietary pattern or prevalence of intestinal overgrowth, fasting ethanol levels being positively associated with measures of insulin resistance were significantly higher in children with NAFLD than in controls. Ethanol levels were similar in portal vein and chyme obtained from different parts of the GI tract between groups while ethanol levels in vena cava plasma were significantly higher in ob/ob mice. ADH activity was significantly lower in liver tissue obtained from ob/ob mice in comparison to wild-type controls and ob/ob mice treated with aT. CONCLUSIONS: Taken together, our data of animal experiments suggest that increased blood ethanol levels in patients with NAFLD may result from insulin-dependent impairments of ADH activity in liver tissue rather than from an increased endogenous ethanol synthesis. TRIAL REGISTRATION NUMBER: NCT01306396.

The role of intestinal microbiota in murine models of acetaminophen-induced hepatotoxicity.

BACKGROUND & AIMS: Variations in intestinal microbiota may influence acetaminophen metabolism. This study aimed to determine whether intestinal microbiota are a source of differential susceptibility to acetaminophen-induced hepatotoxicity. METHODS: Conventionally housed C3H/HeH (CH) and C3H/HeH germ-free (GF) mice were administered a 200 mg/kg IP dose of acetaminophen. The severity of hepatotoxicity at 8 h was assessed by histology and biochemical indices. A urinary metabolic profile was obtained using (1) H-NMR. Baseline hepatic glutathione content and CYP2E1 expression were quantified. An additional group of C3H/HeJ (LPS-r) mice were assessed to determine the contribution of LPS/TLR4 signalling. RESULTS: Baseline glutathione levels were significantly reduced (P = 0.03) in GF mice. CYP2E1 mRNA expression and protein levels were not altered. Interindividual variability did not differ between GF and CH groups. No significant differences in the extent of hepatocellular injury (ALT or percentage necrosis) were demonstrated. However, a milder acute liver failure (ALF) phenotype was shown in GF compared with CH mice, with reduced plasma bilirubin and creatinine and increased blood glucose. Differential acetaminophen metabolism was demonstrated. GF mice displayed a higher urinary acetaminophen-sulphate:glucuronide ratio compared with CH (P = 0.01). Urinary analysis showed metabolic differentiation of GF and CH groups at baseline and 8 h (cross-validated anova P = 1 × 10(-22) ). Interruption of TLR4 signalling in LPS-r mice had additional protective effects. CONCLUSION: Variations in intestinal microbiota do not fully explain differential susceptibility to acetaminophen-induced hepatotoxicity. GF mice experienced some protection from secondary complications following acetaminophen overdose and this may be mediated through reduced TLR4/LPS signalling.

Comparison of circulating, hepatocyte specific messenger RNA and microRNA as biomarkers for chronic hepatitis B and C.

Circulating microRNAs have been widely recognized as a novel category of biomarker in a variety of physiological and pathological conditions. Other reports revealed that fragments of organ specific messenger RNAs are also detectable in serum/plasma and can be utilized as sensitive indicators of liver pathology and cancer. In order to assess the sensitivity and reliability of these two class of RNAs as marker of hepatitis B or C induced chronic liver disease, we collected plasma samples from 156 chronic hepatitis B or C patients (HBV active n = 112, HBV carrier n = 19, hepatitis C n = 25) and 22 healthy donors and quantified their circulating mRNA for albumin, HP (haptoglobin), CYP2E1 (cytochrome P450, family 2, subfamily E) and ApoA2 (Apolipoprotein A2) in conjunction with microRNA-122, a well established marker for acute and chronic liver injury. We found that plasma microRNA-122 level is significantly elevated in patients with active HBV but not in HBV carriers. Furthermore, microRNA-122 is not elevated in HCV patients even though their median serum alanine aminotransferase (sALT) was three fold of the healthy donors. Nevertheless, circulating mRNAs, especially albumin mRNA, showed much more sensitivity in distinguishing active hepatitis B, hepatitis B carrier or HCV patients from healthy control. Correlation and multiple linear regression analysis suggested that circulating mRNAs and miRNAs are much more related to HBsAg titre than to sALT. Immunoprecipitation of HBsAg in HBV patients' plasma resulted in enrichment of albumin and HP mRNA suggesting that fragments of liver specific transcripts can be encapsidated into HBsAg particles. Taken together, our results suggest that hepatocyte specific transcripts in plasma like albumin mRNA showed greater sensitivity and specificity in differentiating HBV or HCV induced chronic liver disease than microRNA-122. Circulating mRNA fragments merit more attention in the quest of next generation biomarkers for various maladies.

Biochemical and molecular mechanisms of N-acetyl cysteine and silymarin-mediated protection against maneb- and paraquat-induced hepatotoxicity in rats.

Oxidative stress is one of the major players in the pathogenesis of maneb (MB) and paraquat (PQ)-induced disorders. N-acetyl cysteine (NAC), a glutathione (GSH) precursor and silymarin (SIL), a naturally occurring antioxidant, encounter oxidative stress-mediated cellular damage. The present study was aimed to investigate the effects of NAC and SIL against MB and/or PQ-induced hepatotoxicity in rats. The levels of hepatotoxicity markers - alanine aminotransaminase (ALT), aspartate aminotransaminase (AST) and total bilirubin, histological changes, oxidative stress indices, phase I and phase II xenobiotic metabolizing enzymes - cytochrome P450 (CYP) and glutathione S-transferase (GST) and pro-inflammatory molecules - inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) were measured in animals treated with MB and/or PQ in the presence or absence of NAC and SIL. MB and/or PQ augmented ALT, AST, total bilirubin, lipid peroxidation and nitrite contents and catalytic activities of superoxide dismutase and glutathione peroxidase however, the GSH content was attenuated. NAC and SIL restored the above-mentioned alterations towards basal levels but the restorations were more pronounced in SIL treated groups. Similarly, MB and/or PQ-mediated histopathological symptoms and changes in the catalytic activities/expressions of CYP1A2, CYP2E1, iNOS, TNF-α, and IL-1ß were alleviated by NAC and SIL. Conversely, MB and/or PQ-induced GSTA4-4 expression/activity was further increased by NAC/SIL and glutathione reductase activity was also increased. The results obtained thus suggest that NAC and SIL protect MB and/or PQ-induced hepatotoxicity by reducing oxidative stress, inflammation and by modulating xenobitic metabolizing machinery and SIL seems to be more effective.

CYP2E1 phenotype in Mexican workers occupationally exposed to low levels of toluene.

UNLABELLED: CYP2E1, an inducible enzyme present in different human tissues, metabolizes several potentially toxic substances including many volatile organic compounds (VOCs). One indirect way to monitor exposure to VOCs may be, therefore, the assessment of CYP2E1 activity in vivo using the chlorzoxazone (CHZ) test. GOAL: To compare CYP2E1 activity in two groups of workers: one with a known occupational exposure to VOCs (exposed group) and the other employed in administrative tasks at two universities (control group) from the city of León, Guanajuato, México. MATERIAL AND METHODS: (1) Passive diffusion monitors were used to evaluate individual levels of exposure to toluene, benzene and ethylbenzene in 48 persons (24 tannery workers and 24 administrative controls) during a 8h work shift; (2) after 12h fasting 500mg CHZ, a selective probe for assessing CYP2E1 activity, was orally administered and, after 2h, a venous blood sample was collected for HPLC plasmatic quantitative determination of CHZ and its mean metabolite 6-hydroxychlorzoxazone. RESULTS: Toluene mean exposure levels were higher in the exposed group (2.86±2ppm vs. 0.05±0.005ppm; p<0.001). Also, in this group CYP2E1 activity was lower (p<0.05) and it decreased as the accumulated months of labor exposure increased (negative correlation, p<0.05). These results are in line with previous findings obtained from shoemakers exposed to various solvents but, interestingly, they are partly in contrast with those of another study in printers. CONCLUSION: In spite of the relatively low levels of toluene exposure found for tannery workers, an effect on CYP2E1 activity was evident. Although the mechanism of this interaction is still unknown, the decrease in CYP2E1 activity per se might represent a health risk, considering that these workers may be less protected against other CYP2E1 substrates present in the labor setting or derived from an intentional exposure.

Depression by a green tea extract of alcohol-induced oxidative stress and lipogenesis in rat liver.

We determined the effects of a green tea extract with 36% alcohol on the blood alcohol content, oxidative stress, lipogenesis, inflammation and liver function of female Wistar rats. Tea alcohol significantly decreased the O2⁻, H2O2 and HOCl amounts via catechins and not caffeine. Thirty days of alcohol gavage improved the level of reactive oxygen species (ROS) in the liver, bile and blood, increased the 4-hydroxynonenal-protein adducts, Kupffer cell infiltration and lipid accumulation in the liver, and elevated the plasma alanine aminotransferase level. A western blot analysis showed reduced expression of the oxidative enzymes (CYP2E1 and NADPH oxidase p47phox protein) and lipogenic enzymes (SREBP-1c and fatty acid synthase) in the alcohol-treated liver. Tea alcohol significantly attenuated these elevated parameters. We conclude that the green tea extract in alcohol efficiently reduced the amounts of O2⁻, H2O2 and HOCl primarily due to the catechin content, and not caffeine. The developed tea liquor attenuated alcohol-induced oxidative injury and lipogenesis in the liver by the synergetic action of catechins and caffeine.

Induction of blood lymphocyte cytochrome P450 2E1 in early stage alcoholic liver cirrhosis.

To validate the induction of blood lymphocyte cytochrome P450 2E1 (CYP2E1) expression in alcoholic liver cirrhosis and mRNA and protein expression of CYP2E1 in freshly prepared blood lymphocytes of alcoholic liver cirrhotic (ACP), nonalcoholic cirrhotic patients (NACP), alcoholic controls (ACs), and nonalcoholic controls (NACs) were investigated. Registered ACP and NACP patients at Sanjay Gandhi Postgraduate Institute of Medical Science, Lucknow, India along with NACs and ACs were included in the study. Real time polymerase chain reaction, enzyme-linked immunosorbent assay, and CYP2E1-dependent enzyme activity were determined in blood lymphocytes isolated from cases and controls. Significant increases in CYP2E1 mRNA and protein expression were observed in freshly prepared blood lymphocytes isolated from ACs and ACP patients as compared with respective NACs or NACP patients. A concomitant increase in N-nitrosodimethyamine demethylase activity was evident in the blood lymphocytes of ACs and ACP patients. Interestingly, the comparative increase observed in CYP2E1 expression was of greater magnitude in the blood lymphocytes isolated from ACP patients, although they abstained from alcohol drinking. Findings suggest that significant increase in the CYP2E1 mRNA and protein expression in the blood lymphocytes, isolated from early stage ACP patients, can be used to predict alcohol-induced toxicity.

CYP2E1 mRNA expression, genetic polymorphisms in peripheral blood lymphocytes and liver abnormalities in Chinese VCM-exposed workers.

OBJECTIVE: To study the relationship between expression of cytochrome P4502E1 (CYP2E1) in human lymphocytes, variant CYP2E1 genotype, exposure to vinyl chloride monomer (VCM), and liver abnormalities in VCM-exposed workers. METHODS: A case-control study was performed on 90 male occupationally exposed workers and 42 matched male nonexposed controls. Data were collected based on health surveillance, workplace investigation and questionnaire Survey. Total RNA and DNA were isolated from peripheral blood lymphocytes, and CYP2E1 mRNA expression was determined using RT-PCR, and the presence of CYP2E1 polymorphisms was identified based on PCR-RFLP. RESULTS: The mRNA expression of CYP2E1 in exposed workers (0.89+/-0.46) was significantly higher than in nonexposed controls (0.61+/-0.35) (P < 0.01). Logistic regression analysis demonstrated a statistically significant association between CYP2E1 mRNA expression levels and liver abnormalities in the VCM-exposed workers (OR = 3.66, P < 0.05). The genotype frequency for CYP2E1 variants among VCM-exposed workers was not significantly different between workers with liver abnormalities and those without. CONCLUSIONS: Liver abnormalities in subjects exposed to VCM are positively associated with expression of peripheral blood lymphocyte mRNA, which is significantly increased in exposed workers compared to nonexposed controls. Therefore, CYP2E1 mRNA levels may be useful for health surveillance and protection of VCM-exposed workers.

Phenotyping of cytochrome P450 2E1 in vitro and in vivo.

The aim of the present study was to develop and improve methods for phenotyping of CYP2E1, an important enzyme in the biotransformation of many industrial chemicals, therapeutic drugs and endogenous substances. The possibility to measure CYP2E1 activity in lymphocytes by using p-nitrophenol as a substrate and CYP2E1 protein levels by flow cytometry were studied in vitro. Further, the conventional chlorzoxazone method for in vivo phenotyping was studied by adjusting the dose to body weight in 10 healthy volunteers. Finally, the possibility to obtain the chlorzoxazone metabolic ratio in saliva samples was investigated. No CYP2E1 protein in lymphocytes was detected by using flow cytometry. Some enzyme activity was found in the experiments with p-nitrophenol, however, it could not be verified that it was catalyzed by CYP2E1. Chlorzoxazone and 6-hydroxychlorzoxazone were not detectable in saliva samples. The present in vivo experiments, combined with our previous data (in total 356 experiments in 50 subjects) show that the metabolic ratio increases with decreasing absorbed dose, expressed as the sum of chlorzoxazone and 6-hydroxychlorzoxazone in plasma at 2 h. The increase becomes pronounced at sum concentrations below 100 microM. In conclusion, chlorzoxazone metabolism in vivo remains the only available method for CYP2E1 phenotyping. The administered dose as well as the absorption of the probe influences the chlorzoxazone ratio. We suggest that a dose of 10 mg chlorzoxazone per kg body weight is used to estimate the CYP2E1 phenotype. Further, metabolic ratios should be disregarded if the sum of plasma chlorzoxazone and 6-hydroxychlorzoxazone is below 100 microM (blood sampled after 2 h).

The effect of genetic polymorphisms in the vinyl chloride metabolic pathway on mutagenic risk.

Vinyl chloride (VC) is a human carcinogen known to undergo metabolism by cytochrome P450 2E1 (CYP2E1) to reactive intermediates that can cause oncogene and tumor suppressor gene mutations and that are further metabolized by acetaldehyde dehydrogenase (ALDH2) and glutathione-S-transferases (GSTs) to non-mutagenic end products. These metabolic enzymes have known polymorphisms that could lead to increased levels of the VC reactive intermediates and thus an increased risk for mutations and cancer following exposure. Using restriction fragment length polymorphism (RFLP) analysis, we have examined a cohort of 597 French VC workers for polymorphisms in CYP2E1, ALDH2, GSTM1 and GSTT1 in relation to the occurrence of mutant oncogene and tumor suppressor gene biomarkers that are attributable to VC exposure. The presence of the biomarkers for mutant ras-p21 and mutant p53 was found to be highly significantly associated with cumulative VC exposure (P for trend <0.0001). The presence of the CYP2E1 variant c2 allele was found to be significantly associated with the presence of either or both mutant biomarkers even after controlling for potential confounders including cumulative VC exposure (OR = 2.3, 95% CI = 1.2-4.1), and the effects of the c2 allele and VC exposure were approximately additive. GSTT1 null status was found to have an increased, but not significant association with the presence of either or both biomarkers after controlling for confounders (OR = 1.3, 95% CI = 0.8-2.0). These results suggest the existence of a possible gene-environment interaction between polymorphisms in the VC metabolic pathway and VC exposure that could contribute to the variable susceptibility to the mutagenic effects of VC in exposed populations.

Cytochrome P4502E1 (CYP2E1) expression in peripheral blood lymphocytes: evaluation in hepatitis C and diabetes.

OBJECTIVE: Cytochrome P4502E1 (CYP2E1) is expressed in human peripheral blood lymphocytes (PBLs), and previous reports have suggested the possibility of using this readily available tissue as a reporter of CYP2E1 status. To further explore the relevance of this approach we assessed CYP2E1 expression in PBLs in two contrasting conditions, chronic hepatitis C and insulin-dependent diabetes (IDD), illustrating an organ and a systemic disease, respectively. METHODS: Total RNA was isolated from extracted PBLs (hepatitis C patients + IDD) and by percutaneous needle biopsy (hepatitis C patients only). Gene expression for CYP2E1 was determined by real-time reverse-transcription polymerase chain reaction. Histological changes in liver tissue were assessed according to Ludwig's criteria. RESULTS: In patients with chronic hepatitis C a clear relationship was found between CYP2E1 expression in the liver and the progression of hepatic disease (both lobular inflammation and fibrosis indices), and observed variations were consistent with the preferential distribution of CYP2E1 in the lobular zone. No effect of the liver disease was, however, found at the PBL level. A statistically significant increase in mean CYP2E1 expression level was observed in the lymphocytes from poorly controlled IDD subjects compared to controls. CONCLUSIONS: Taken together, our data indicate that the measurement of CYP2E1 expression in PBLs is not useful in liver diseases. However, in a systemic condition (IDD) this measurement can be proposed for monitoring the CYP2E1 induction in a relatively noninvasive manner. This tool should therefore be further validated in clinical field or experimental studies for CYP2E1 phenotyping purposes.