Low doses of nicotine and ethanol induce CYP2E1 and chlorzoxazone metabolism in rat liver

Cytochrome P450 4F isoforms catalyze the hydroxylation of eicosanoids such as leukotriene B(4), prostaglandins, and lipoxins as well as hydroxyeicosatetraenoic acids. In the present study, we report the molecular cloning of two novel mouse CYP4F isoforms, CYP4F15 and CYP4F16. Sequence comparison showed that CYP4F15 has 93.5% homology to CYP4F4 and CYP4F16 has 90.8% homology to CYP4F5, therefore they are the orthologs for rat CYP4F4 and CYP4F5, respectively. Both isoforms are expressed in liver and also in extrahepatic tissues but the patterns of expression are slightly different. To elucidate further the regulation and regulatory mechanism of the two isoforms, renal and hepatic CYP4F15 and CYP4F16 expression were analyzed using wild-type (SV/129) mice and peroxisome proliferator-activated receptor (PPAR) alpha null mice with or without challenge by bacterial endotoxin (LPS) or clofibrate. Renal expression of CYP4F15 was induced by LPS and clofibrate in (+/+) mice, and these effects were absent in the (-/-) mice. Renal expression of CYP4F16 was not affected by LPS or clofibrate in (+/+) or (-/-) mice. In contrast, hepatic expression of CYP4F15 and CYP4F16 was significantly reduced by LPS-treatment in (+/+) mice. A lesser reduction was also seen in the (-/-) mice, suggesting that PPARalpha is partially responsible for this down-regulation. Clofibrate treatment caused the reduction of hepatic CYP4F16 expression and this effect was not dependent on PPARalpha. Clofibrate treatment had no effect on hepatic CYP4F15 expression. Together, our data indicate that CYP4Fs are regulated in an isoform-specific, tissue-specific, and species-specific manner.     

Inactivation of hepatic CYP2E1 by an epoxide of diallyl sulfone

Diallyl sulfone (DASO(2)) inhibits hepatic CYP2E1. In this investigation, we have tested the hypothesis that an epoxide formed from DASO(2) is responsible for inactivation of hepatic CYP2E1 in mice. An epoxide of DASO(2) (1,2-epoxypropyl-3, 3'-sulfonyl-1'-propene; DASO(3)) was synthesized and conjugated to glutathione (GSH) to produce the conjugates S-(1R,S-[[ 1-hydroxymethyl-2,3'-sulfonyl]-1'-propenyl]ethyl)glutathione (diastereomers) and S-(1-[[2R,S-hydroxypropyl]-3, 3'-sulfonyl]-1'-propenyl)glutathione (diastereomers). Their identities were confirmed by (1)H NMR analysis, and these were used as analytical standards. HPLC analysis revealed a major peak for the GSH conjugates that eluted at 20.5 min. This peak was detected in liver microsomal incubations performed with DASO(2) in the presence of NADPH. A similar peak also was detected in incubations of CYP2E1-expressed lymphoblastoid microsomes, NADPH and DASO(2). The generation of the epoxide-derived GSH conjugates in the microsomal incubations was concentration-dependent, and reached saturation at 0. 75 to 1.0 mM DASO(2). Formation of the conjugates was also time-dependent and peaked at 2.0 h after DASO(2). Levels of DASO(3) formed from DASO(2), as estimated by production of a 4-(p-nitrobenzyl)pyridine derivative, were maximal at 1 mM DASO(2) at 30 min. CYP2E1-dependent p-nitrophenol hydroxylase activity was decreased in microsomes incubated with DASO(2), with alterations that were proportional to the concentration of DASO(2) (0.25-1.0 mM) used. Dose-dependent decreases in hydroxylase activity also were found in microsomes from mice treated in vivo with DASO(2) (25-200 mg/kg). These DASO(2)-induced decreases corresponded with reduced amounts of immunodetectable CYP2E1. Levels of spectrally detectable P450 and heme were both diminished by DASO(2). These results supported the contention that an epoxide formed from DASO(2) mediates the inactivation of hepatic CYP2E1.     

S-adenosyl-L-methionine attenuates hepatotoxicity induced by agonistic Jo2 Fas antibody following CYP2E1 induction in mice

S-Adenosyl-l-methionine (SAM) has been shown to be hepatoprotective against many toxic agents. Its possible effectiveness in protecting against CYP2E1-dependent toxicity is not known. We recently reported that treatment of mice with pyrazole to induce CYP2E1 increased hepatotoxicity produced by Fas agonistic Jo2 antibody. The current study was designed to investigate the effect of exogenous administration of SAM on the synergistic hepatotoxicity produced by Fas agonistic Jo2 antibody plus CYP2E1 following pyrazole pretreatment in C57BL/6 mice. Suboptimal administration of Jo2 Fas antibody combined with pyrazole pretreatment caused severe hepatotoxicity as determined by elevations in serum transaminase levels and histopathology. Exogenous administration of SAM (50 mg i.p./kg body weight every 12 h for 3 days) significantly decreased serum transaminases and ameliorated morphological changes of the liver. Addition of SAM elevated hepatic SAM and total reduced glutathione levels and inhibited CYP2E1 activity. SAM also lowered the elevated oxidative stress (lipid peroxidation, protein carbonyls, and superoxide production) and nitrosative stress (induction of inducible nitric-oxide synthase and 3-nitrotyrosine adducts) and increases in caspase-8 and -3 activation produced by the pyrazole plus Jo2 treatment. SAM did not prevent the increase in serum TNF-alpha levels or the decrease in catalase activity in this model. These results indicate that SAM can have an important hepatoprotective role as an effective reagent against Fas plus CYP2E1-induced hepatotoxicity by lowering oxidative and nitrosative stress.     

Potentiation of thioacetamide liver injury in diabetic rats is due to induced CYP2E1

Thioacetamide (TA)-induced hepatotoxicity is potentiated in streptozotocin (STZ)-induced diabetic rats. The relative roles of CYP2E1 and FMO1 in the mechanism of TA-associated liver injury were investigated. In the STZ-induced diabetic rat, hepatic CYP2E1 protein concentration and p-nitrophenol hydroxylation were induced 8- and 5.6-fold, respectively. Pretreatment with the CYP2E1 inducer, isoniazid (INH, 250 mg/kg, i.p.) before TA (300 mg/kg, i.p.) administration significantly increased TA-associated liver injury as assessed by plasma alanine aminotransferase (ALT). Hepatic CYP2E1 expression and p-nitrophenol hydroxylation were induced 2.2- and 2. 5-fold in the INH-pretreated rat, respectively. Inhibition of CYP2E1 by diallyl sulfide (DAS, 200 mg/kg, p.o., two doses) before TA administration, decreased plasma ALT activity by 60% in the nondiabetic rat and by 75% in the diabetic rat. Abolition of microsomal p-nitrophenol hydroxylation and CCl(4)-induced liver injury confirmed that hepatic CYP2E1 was highly inhibited by DAS. Hepatic flavin-containing monooxygenase (FMO) form 1 expression and methimazole-dependent oxidation of thiocholine were induced 2.5- and 1.8-fold in the diabetic rat, respectively. Dietary administration of 0.25% indole-3-carbinol (I3C) for 10 days inhibited FMO1 expression and enzyme activity in both nondiabetic and diabetic rats. Paradoxically, TA-induced liver injury was increased in these I3C-pretreated rats. These findings indicate that hepatic CYP2E1 appears to be primarily involved in bioactivation of TA. In the STZ-induced diabetic rat, diabetes-induced CYP2E1 appears to be responsible for the potentiated liver injury; Even though hepatic FMO1 is induced in the diabetic rat, it is unlikely to mediate the potentiated TA hepatotoxicity.     

Pharmacogenetics of acenocoumarol: CYP2C9, CYP2C19, CYP1A2, CYP3A4, CYP3A5 and ABCB1 gene polymorphisms and dose requirements

BACKGROUND AND OBJECTIVE: Acenocoumarol (AC) is a coumarin derivative, vitamin K antagonist anticoagulant drug. It has a narrow therapeutic index and shows large pharmacokinetic and pharmacodynamic interindividual variability. Our objective was to investigate the association between AC dose requirements to achieve a target level of anticoagulation and genetic polymorphisms of genes possibly associated with its metabolism (CYP1A2, CYP2C9, CYP2C19, CYP3A4, CYP3A5) and transport (ABCB1). METHODS: Ninety-six Bulgarian patients treated orally with AC for at least 3 months were included. They were separated into three groups according to their AC dose requirement, i.e. low, medium and high. RESULTS AND DISCUSSION: CYP2C9*1/*3 (associated with an intermediate CYP2C9 activity), CYP2C9*2/*2, and CYP2C9*2/*3 genotypes (associated with a low CYP2C9 activity) were more prevalent in the group with low dose requirement of AC compared with the other two groups (P = 0.003). The frequency of CYP2C9*1/*1 genotype, which is associated with an extensive CYP2C9 activity, was higher in the group of patients with high dose requirements (79%), compared with the groups of the medium and low dose requirements (67% and 21% respectively). In addition, the ABCB1 2677GG/3435CC haplotype was associated with use of lower AC dose, whereas the 2677TT/3435TT and 2677GT/3435TT haplotypes were associated with use of higher AC dose (P = 0.03). The distribution of polymorphisms of other genes did not show significant differences between the three groups. CONCLUSION: In vivo, cytochromes P450 isoforms other than CYP2C9 [corrected] were not significantly associated with dose requirement of AC. In our Bulgarian patients, the presence of CYP2C9*2 or/and CYP2C9*3 alleles, as well as the ABCB1 2677GG/3435CC haplotype were associated with low dose requirement of AC.     

Cytochrome P450 2E1 (CYP2E1) is the principal enzyme responsible for urethane metabolism: comparative studies using CYP2E1-null and wild-type mice

Urethane ([carbonyl-(14)C]ethyl carbamate) is a fermentation by-product in alcoholic beverages and foods and is classified as reasonably anticipated to be a human carcinogen. Early studies indicated that while CYP2E1 is involved, esterases are the primary enzymes responsible for urethane metabolism. Using CYP2E1-null (KO) mice, current studies were undertaken to elucidate CYP2E1's contribution to urethane metabolism. [Carbonyl-(14)C]urethane was administered by gavage to male CYP2E1-null and wild-type mice at 10 or 100 mg/kg and its metabolism and disposition were investigated. CO(2) was confirmed as the main metabolite of urethane. Significant inhibition of urethane metabolism to CO(2) occurred in CYP2E1-null versus wild-type mice. Pharmacokinetic modeling of (14)CO(2) exhalation data revealed that CYP2E1 is responsible for approximately 96% of urethane metabolism to CO(2) in wild-type mice. The contributions of other enzymes to urethane metabolism merely account for the remaining 4%. The half-life of urethane in wild-type and CYP2E1-null mice was estimated at 0.8 and 22 h, respectively. Additionally, the concentration of urethane-derived radioactivity in blood and tissues was dose-dependent and significantly higher in CYP2E1-null mice. High-performance liquid chromatography analysis showed only urethane in the plasma and liver extracts of CYP2E1-null mice. Because the lack of CYP2E1 did not completely inhibit urethane metabolism, the disposition of 10 mg/kg urethane was compared in mice pretreated with the P450 inhibitor, 1-aminobenzotriazole or the esterase inhibitor, paraoxon. Unlike paraoxon, 1-aminobenzotriazole resulted in significant inhibition of urethane metabolism to CO(2) in both genotypes. In conclusion, this work demonstrated that CYP2E1, not esterase, is the principal enzyme responsible for urethane metabolism.     

Suppression of hepatic CYP3A1/2 and CYP2C11 by cyclosporine is not mediated by altering growth hormone levels

Cyclosporine (CsA) suppresses drug metabolism by decreasing cytochrome P450 (P450) enzyme levels in rat liver. Growth hormone (GH) is known to pretranslationally regulate P450 expression. Thus, the suppression of P450 by CsA may involve GH as an intermediate. To address this question, we examined the effects of administering exogenous GH via twice daily subcutaneous injections and in conjunction with chronic subcutaneous CsA administration for 14 days on hepatic P450 expression. CsA alone decreased CYP3A1/2 and CYP2C11 significantly, in a manner similar to that previously found. When administered in the absence of CsA, GH also suppressed CYP3A1/2 and CYP2C11 protein levels as compared with GH vehicle. In the presence of CsA, GH did not cause further suppression of either CYP3A1/2 or CYP2C11 expression when compared with CsA treatment with GH vehicle. Testosterone in vitro catalytic assays confirmed that CsA and GH separately cause significant decreases in activity levels. Also, the concomitant administration of GH and CsA caused lowered production of 16alpha-, 2alpha-, 6beta-, and 2beta-hydroxytestosterone as compared with the administration of GH with CsA vehicle and as compared with the administration of GH vehicle with CsA. This study shows that GH is a dominating factor over CsA in determining hepatic P450 expression and activity. In addition, CsA does not seem to alter GH levels as a mediating event in suppressing P450 expression and activity. Since CsA given in combination with GH further suppressed P450 activity as compared with CsA given in combination with vehicle, this suggests that changes in hormonal status are likely to be one of the many factors that is responsible for the lack of a clear association between cyclosporine dosing and markers of toxicity.     

Bioactivation of 1,1-dichloroethylene by CYP2E1 and CYP2F2 in murine lung

1,1-Dichloroethylene (DCE) exposure evokes lung toxicity with selective damage to bronchiolar Clara cells. Recent in vitro studies have implicated CYP2E1 and CYP2F2 in the bioactivation of DCE to 2-S-glutathionyl acetate [C], a putative conjugate of DCE epoxide with glutathione. An objective of this study was to test the hypothesis that bioactivation of DCE is catalyzed by both CYP2E1 and CYP2F2 in murine lung. Western blot analysis of lung microsomal proteins from DCE-treated CD-1 mice showed time-dependent loss of immunodetectable CYP2F2 and CYP2E1 protein. Dose-dependent formation of conjugate [C] was observed in the lungs of CD-1 mice treated with DCE (75-225 mg/kg), but it was not detected after pretreatment with 5-phenyl-1-pentyne (5-PIP). Treatment of mice with 5-PIP and also with diallyl sulfone (DASO2) significantly inhibited hydroxylation of p-nitrophenol (PNP) and chlorzoxazone (CHZX). Incubation of recombinant CYP2F3 (a surrogate for CYP2F2) and recombinant CYP2E1 with PNP and CHZX confirmed that they are substrates for both of the recombinant enzymes. Incubation of the recombinant enzymes with DASO2 or 5-PIP significantly inhibited hydroxylation of both PNP and CHZX. Bronchiolar injury was elicited in CD-1 mice treated with DCE (75 mg/kg), but it was abrogated with 5-PIP pretreatment. Bronchiolar toxicity also was manifested in the lungs of CYP2E1-null and wild-type mice treated with DCE (75 mg/kg), but protection ensued after pretreatment with 5-PIP or DASO2. These results showed that bioactivation of DCE in murine lung occurred via the catalytic activities of both CYP2E1 and CYP2F2 and that bioactivation by these enzymes mediated the lung toxicity.     

Identification of novel CYP2A6*1B variants: the CYP2A6*1B allele is associated with faster in vivo nicotine metabolism

Cytochrome P450 2A6 (CYP2A6) is the human enzyme responsible for the majority of nicotine's metabolism. CYP2A6 genetic variants contribute to the interindividual and interethnic variation in nicotine metabolism. We examined the association between the CYP2A6*1B variant and nicotine's in vivo metabolism. Intravenous infusions of deuterium-labeled nicotine were administered to 292 volunteers, 163 of whom were White and did not have common CYP2A6 variants, other than CYP2A6*1B. We discovered three novel CYP2A6*1B variants in the 3'-flanking region of the gene that can confound genotyping assays. We found significant differences between CYP2A6*1A/*1A, CYP2A6*1A/*1B, and CYP2A6*1B/*1B groups in total nicotine clearance (17.2+/-5.2, 19.0+/-6.4, and 20.4+/-5.9, P<0.02), non-renal nicotine clearance (16.4+/-5.0, 18.5+/-6.2, and 19.8+/-5.7, P<0.01), and the plasma trans-3'-hydroxycotinine/cotinine ratio (0.26+/-0.1, 0.26+/-0.1, and 0.34+/-0.1, P<0.001). There were also differences in total nicotine (29.4+/-12.9, 25.8+/-0.12.9, and 22.4+/-12.4, P<0.01), cotinine (29.2+/-8.1, 32.2+/-9.1, and 33.0+/-6.6, P<0.01) and trans-3'-hydroxycotinine (32.4+/-9.1, 34.2+/-12.3, and 41.3+/-11.3, P<0.001) excreted in the urine. We report evidence that CYP2A6*1B genotype is associated with faster nicotine clearance in vivo, which will be important to future CYP2A6 genotype association studies.     

Analysis of differential substrate selectivities of CYP2B6 and CYP2E1 by site-directed mutagenesis and molecular modeling

Human CYP2B6 and CYP2E1 were used to investigate the extent to which differential substrate selectivities between cytochrome P450 subfamilies reflect differences in active-site residues as opposed to distinct arrangement of the backbone of the enzymes. Reciprocal CYP2B6 and CYP2E1 mutants at active-site positions 103, 209, 294, 363, 367, and 477 (numbering according to CYP2B6) were characterized using the CYP2B6-selective substrate 7-ethoxy-4-trifluoromethylcoumarin, the CYP2E1-selective substrate p-nitrophenol, and the common substrates 7-ethoxycoumarin, 7-butoxycoumarin, and arachidonic acid. This report is the first to study the active site of CYP2E1 by systematic site-directed mutagenesis. One of the most intriguing findings was that substitution of CYP2E1 Phe-477 with valine from CYP2B6 resulted in significant 7-ethoxy-4-trifluoromethylcoumarin deethylation. Use of three-dimensional models of CYP2B6 and CYP2E1 based on the crystal structure of CYP2C5 suggested that deethylation of 7-ethoxy-4-trifluoromethylcoumarin by CYP2E1 is impeded by van der Waals overlaps with the side chain of Phe-477. Interestingly, none of the CYP2B6 mutants acquired enhanced ability to hydroxylate p-nitrophenol. Substitution of residue 363 in CYP2E1 and CYP2B6 resulted in significant alterations of the metabolite profile for the side chain hydroxylation of 7-butoxycoumarin. Probing of CYP2E1 mutants with arachidonic acid indicated that residues Leu-209 and Phe-477 are critical for substrate orientation in the active site. Overall, the study revealed that differences in the side chains of active-site residues are partially responsible for differential substrate selectivities across cytochrome P450 subfamilies. However, the relative importance of active-site residues appears to be dependent on the structural similarity of the compound to other substrates of the enzyme.     

Pharmacodynamics of carbamazepine-mediated induction of CYP3A4, CYP1A2, and Pgp as assessed by probe substrates midazolam, caffeine, and digoxin

The aim of this study was to develop a model describing the carbamazepine autoinduction and the carbamazepine-mediated induction of CYP3A4, CYP1A2, and P-glycoprotein. Seven healthy volunteers were dosed with carbamazepine over 16 consecutive days. The CYP3A4, CYP1A2, and P-glycoprotein activities were assessed, using midazolam, caffeine, and digoxin as probe substrates, on 12 occasions, covering the preinduced state and the onset and termination of the induction process. The data were evaluated using a mechanistic pharmacokinetic approach in NONMEM. The induction processes were described using turnover models, with carbamazepine and carbamazepine-10,11-epoxide as the driving force of the induction. The half-lives of CYP3A4 and CYP1A2 were estimated to be 70 and 105 h, respectively. P-glycoprotein was not affected by the carbamazepine treatment. The possibility of modeling the pharmacodynamics of enzyme induction using a turnover model was illustrated, and the time course of the process was estimated with good precision.     

Genetic polymorphisms of drug-metabolizing phase I enzymes CYP2E1, CYP2A6 and CYP3A5 in South Indian population

CYP2E1, CYP2A6 and CYP3A5 enzymes belong to phase I group of drug-metabolizing enzymes, which are involved in the metabolism of various compounds and xenobiotics. Presence of polymorphisms in the genes coding for these enzymes results in interindividual variations in drug metabolism, therapeutic response and susceptibility towards various diseases. The frequencies of these variants in genes differ considerably between ethnic groups. This study was carried out to estimate the allele and genotype frequencies of common variants in CYP2E1, CYP2A6 and CYP3A5 in South Indian population. Six hundred and fifty-two unrelated healthy volunteers of South Indian origin (Andhra Pradesh, Karnataka, Kerala and Tamil Nadu) were included in this study. Polymerase chain reaction-restriction fragment length polymorphism, allele-specific PCR, real-time PCR, SNaPshot and gene sequencing methods were used for the identification of gene polymorphisms. The frequencies of CYP2E1*1B, CYP2E1*5B and CYP2E1*6 alleles in South Indian population were 14.3, 1.3 and 22.4%, respectively. The frequencies of CYP2A6*2, CYP2A6*4A and CYP2A6*5 alleles were found to be 1, 8.9 and 0.7%, respectively. The distribution of CYP3A5*3 allele was 63.5%. There were no variant alleles of CYP3A5*2, CYP3A5*4 and CYP3A5*6 in South Indian population. The frequencies of CYP2E1, CYP2A6 and CYP3A5 in the South Indian population are distinct from Caucasians, Chinese, Japanese, African Americans and other compared populations. This is the first study conducted in the South Indian population with a larger sample size. The findings of our study provide the basic genetic information for further pharmacogenomic investigations in the population.     

Effects of repeated fenfluramine administration on indices of monoamine function in rat brain: pharmacokinetic, dose response, regional specificity and time course data

The pharmacokinetics and neurochemical effects of repeated fenfluramine administration in rats (1-24 mg/kg s.c., b.i.d. for 4 days) were examined with respect to dose dependence, regional specificity and time course of recovery. Fenfluramine administration resulted in parallel increases in plasma and brain concentrations of the drug and its metabolite, norfenfluramine, which were dose-related but nonlinear. Doses of 1 and 2 mg/kg fenfluramine increased brain serotonin (5-HT) and 5-hydroxyindoleacetic acid with no significant effects on 5-HT uptake sites. Higher doses of fenfluramine (4-24 mg/kg) reduced all three brain 5-HT markers with maximal decreases (80%-90%) occurring at 12 mg/kg. High-dose (24 mg/kg) fenfluramine administration led to larger decreases in 5-HT markers in neocortex, striatum and hippocampus than in hypothalamus, brain stem and spinal cord. Following 80% to 90% reductions of the 5-HT markers in neocortex and hippocampus at 18 hr after drug treatment, 5-HT and 5-hydroxyindoleacetic acid returned to control levels by 4 and 16 weeks, respectively, but 5-HT uptake sites initially recovered more slowly, with a 25% reduction still evident at 8 months. At this time 5-HT and 5-hydroxyindoleacetic acid were again reduced. Fenfluramine administration produced dose-dependent and biphasic effects on brain dopamine markers. Increases in homovanillic acid levels were apparent at 2 hr, whereas decreases in the levels of dopamine, homovanillic acid and dihydroxyphenylacetic acid were evident at 18 hr post-treatment. Norepinephrine levels were only decreased by doses of fenfluramine greater than or equal to 4 mg/kg. Fenfluramine administration did not cause long-term alterations in dopamine or norepinephrine uptake sites.(ABSTRACT TRUNCATED AT 250 WORDS)     

CYP2E1, GSTM1 and GSTT1 genetic polymorphisms and susceptibility to antituberculosis drug-induced hepatotoxicity: a nested case-control study

What is Known and Objective: The pathogenic mechanism of antituberculosis drug‐induced hepatotoxicity (ATDH) is thought to involve drug‐metabolizing enzymes including N‐acetyl transferase2 (NAT2), cytochrome P4502E1 (CYP2E1) and glutathione S‐transferase (GST) M1, T1. The associations between genetic polymorphisms of those genes and ATDH have been reported but with inconsistent results. Moreover, most studies were hospital‐based retrospective studies and not prospective. We aimed to investigate possible associations of CYP2E1, GSTM1 and GSTT1 genetic polymorphisms with ATDH using a more robust case–control study nested in a population‐based prospective antituberculosis treatment cohort. Methods: A total of 4304 patients with smear‐positive tuberculosis (TB) who received standard short‐course chemotherapy were monitored for 6–9 months. Incidence density sampling method was adopted to select controls and 4 : 1 matched with each ATDH cases by age (±5 years), sex, treatment history, disease severity and drug dosage. The CYP2E1, GSTM1 and GSTT1 polymorphisms were genotyped using PCR–RFLP and multiplex PCR methods. Conditional logistic regression model was used to calculate odds ratio (OR) and 95% confidence interval (CI), as well as corresponding P‐values. Results and Discussion: A total of 89 ATDH cases and 356 controls were included in this study. There was no statistically significant association between CYP2E1 RsaI c1/c1 genotype or DraI C/C genotype and ATDH (OR = 0·99, 95% CI:0·62–1·59; OR = 1·13, 95% CI: 0·40–3·20, respectively) compared with CYP2E1 RsaI c1/c2 or c2/c2 genotypes or DraI D/D genotype, or between GSTM1/GSTT1 null genotypes and ATDH (OR = 1·22, 95% CI: 0·76–1·96; OR = 0·96, 95% CI: 0·60–1·52, respectively) compared with non‐null genotypes. What is new and Conclusion: This is the first study of the involvement of CYP2E1, GSTM1 and GSTT1 genetic polymorphisms in ATDH using a nested case–control population‐based prospective cohort design. We could not confirm positive associations of genetic polymorphisms of CYP2E1 RsaI, CYP2E1 DraI, GSTM1 null and GSTT1 null with ATDH reported by various groups, in our Chinese TB population.     

Respiratory and locomotor stimulation by low doses of dermorphin, a mu1 receptor-mediated effect

The selective opioid mu receptor agonist dermorphin increased the locomotor activity of rats dose dependently at 10 to 100 pmol/kg i.c.v. Respiratory rate, relative tidal volume and respiratory minute volume also increased unrelated to changes in locomotor activity. Higher doses, on the other hand, produced catalepsy and respiratory depression. Pretreatment of the rats with the mu1-selective antagonist naloxonazine (10 mg/kg i.v.) blocked the stimulant locomotor and respiratory effects of low doses of dermorphin (10-100 pmol/kg), but potentiated the respiratory depressant effect of a high dose (10 nmol/kg) of dermorphin. The selective benzodiazepine antagonist flumazenil (5 mg/kg), which has been shown previously to antagonize catalepsy and respiratory depression produced by relatively high doses of dermorphin, did not antagonize the respiratory or locomotor stimulant effect of dermorphin. The data suggest that mu1-opioid receptors are responsible for the low dose stimulant effects of dermorphin on locomotor activity and respiration whereas mu2 receptors mediate the respiratory depressant effect of dermorphin.     

不同剂量瑞舒伐他汀对氧化修饰低密度脂蛋白诱导单核-巨噬细胞的肝X受体及小凹蛋白1表达的影响

目的 研究不同剂量瑞舒伐他汀对氧化修饰低密度脂蛋白（ox-LDL）诱导的人单核巨噬细胞肝X受体及小凹蛋白1表达的影响.方法 实验分6组：空白对照组、ox-LDL对照组、不同剂量（0.01μmol/L,0.1μmol/L,1.0μmol/L,5.0 μmol/L）瑞舒伐他汀组,RT-PCR法测定各组肝X受体及小凹蛋白1mRNA的表达.结果 空白对照组与ox-LDL对照组肝X受体mRNA的表达分别为1.00±0.02与0.26±0.02,两组比较差异有统计学意义（t=56.392,P＜0.001）;小凹蛋白1mRNA分别为1.00±0.04与0.27±0.01,两组比较差异有统计学意义（t=31.278,P＜0.001）.ox-LDL对照组及不同剂量瑞舒伐他汀组间肝X受体及小凹蛋白1mRNA表达比较,差异均有统计学意义（F值分别为72.154、66.007,P均＜0.001）,随瑞舒伐他汀剂量的增加,肝X受体及小凹蛋白1mRNA表达呈上升趋势,两两比较差异均有统计学意义（P均＜0.05）.结论 瑞舒伐他汀可上调单核-巨噬细胞肝X受体mRNA、小凹蛋白1mRNA的表达,且呈剂量依赖性.     

Phenobarbital induction of CYP6D1 is due to a trans acting factor on autosome 2 in house flies, Musca domestica

To improve our understanding of phenobarbital (PB) mediated induction of CYP6D1 we examined the genetic linkage of PB induction using PB responsive (aabys) and non-responsive (LPR) strains of house flies. PB induction was linked to autosome 2, indicating that CYP6D1 is trans regulated by this PB inducible element. Our results are discussed relative to a previous hypothesis that the same regulatory genes are responsible for both induction and monooxygenase-mediated insecticide resistance.     

Pulmonary bioactivation of 1,1-dichloroethylene is associated with CYP2E1 levels in A/J, CD-1, and C57BL/6 mice

1,1-Dichloroethylene (DCE) elicits lung cytotoxicity and selectively targets Clara cells of bronchioles. The toxic effects are ascribed to CYP2E1-mediated formation of reactive intermediates including the DCE epoxide. Here we tested the hypothesis that differential CYP2E1 levels in the lungs of A/J, CD-1, and C57BL/6 mice lead to differences in the extents of DCE bioactivation and lung damage. Our results showed that lung CYP2E1 levels differed significantly in the three murine strains, and followed the rank order A/J > CD-1 > C57BL/6. Covalent binding of [(14)C]DCE to lung proteins in A/J mice was significantly higher than in either CD-1 or C57BL/6 mice. HPLC analysis of lung cytosol from DCE-treated mice showed that 2-S-glutathionyl acetate, a glutathione (GSH) conjugate derived from the epoxide (conjugate [C]), was the major metabolite formed. Levels of [C] detected in cytosol from A/J and CD-1 mice were significantly higher than in C57BL/6 mice. Immunohistochemical staining for [C] was pronounced in the lungs of A/J mice, was lower in CD-1 mice, and was lowest in C57BL/6 mice. Levels of GSH were similar in the lungs of all untreated mice. However, significant reduction in GSH was found in DCE-treated mice, with decreases comparable in all three strains. Bronchiolar Clara cell damage was more severe in A/J and CD-1 mice than in C57BL/6 mice. These results showed differences in CYP2E1 levels in the lungs of A/J, CD-1, and C57BL/6 mice that correlated with the extent to which the DCE epoxide is formed as well as with the severity of lung cytotoxicity.