Genetic variation in the CYP1A1 gene is related to circulating PCB118 levels in a population-based sample

Several of the polychlorinated biphenyls (PCBs), i.e. the dioxin-like PCBs, are known to induce the P450 enzymes CYP1A1, CYP1A2 and CYP1B1 by activating the aryl hydrocarbon receptor (Ah)-receptor. We evaluated if circulating levels of PCBs in a population sample were related to genetic variation in the genes encoding these CYPs. In the population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study (1016 subjects all aged 70), 21 SNPs in the CYP1A1, CYP1A2 and CYP1B1 genes were genotyped. Sixteen PCB congeners were analysed by high-resolution chromatography coupled to high-resolution mass spectrometry (HRGC/ HRMS). Of the investigated relationships between SNPs in the CYP1A1, CYP1A2 and CYP1B1 and six PCBs (congeners 118, 126, 156, 169, 170 and 206) that captures >80% of the variation of all PCBs measured, only the relationship between CYP1A1 rs2470893 was significantly related to PCB118 levels following strict adjustment for multiple testing (p=0.00011). However, there were several additional SNPs in the CYP1A2 and CYP1B1 that showed nominally significant associations with PCB118 levels (p-values in the 0.003-0.05 range). Further, several SNPs in the CYP1B1 gene were related to both PCB156 and PCB206 with p-values in the 0.005-0.05 range. Very few associations with p<0.05 were seen for PCB126, PCB169 or PCB170. Genetic variation in the CYP1A1 was related to circulating PCB118 levels in the general elderly population. Genetic variation in CYP1A2 and CYP1B1 might also be associated with other PCBs.

CHRNA5-A3-B4 genetic variants alter nicotine intake and interact with tobacco use to influence body weight in Alaska Native tobacco users

BACKGROUND AND AIMS

Gene variants in CHRNA5-A3-B4, which encode for the α5, α3 and β4 nicotinic receptor subunits, are associated with altered smoking behaviors in European Americans. Little is known about CHRNA5-A3-B4 and its association with smoking behaviors and weight in Alaska Native people, which is a population with high prevalence but low levels of tobacco consumption, extensive smokeless tobacco use and high rates of obesity. We investigated CHRNA5-A3-B4 haplotype structure and its association with nicotine intake and obesity in Alaska Native people.

DESIGN, SETTING AND PARTICIPANTS

A cross-sectional study of 400 Alaska Native individuals, including 290 tobacco users.

MEASUREMENTS

CHRNA5-A3-B4 genotype, body weight and tobacco consumption biomarkers such as plasma cotinine and urinary total nicotine equivalents (TNE).

FINDINGS

Alaska Native people have a distinct CHRNA5-A3-B4 haplotype structure compared with European/African Americans. In 290 Alaska Native tobacco users the 'G' allele of rs578776, which tagged a 30 kb haplotype in CHRNA5-A3-B4, was prevalent (16%) and associated significantly with nicotine intake (20% higher plasma cotinine, P < 0.001, 16% higher TNE, P = 0.076), while rs16969968 was not associated with nicotine intake. Rs578776 acted in combination with CYP2A6, the main nicotine-metabolizing enzyme, to increase nicotine intake by 1.8-fold compared with the low-risk group (P < 0.001). Furthermore, rs2869950, a single nucleotide polymorphism 5' to CHRNB4, was associated significantly with increased body mass index (P < 0.01) in the tobacco users even after controlling for differences in nicotine intake (P < 0.01).

CONCLUSIONS

Genetic variants in CHRNA5-A3-B4 alter nicotine intake and body mass index in a population of Alaska Native people, who have a distinct haplotype structure, smoking behaviors and prevalence of obesity.

[Electrochemical sensor systems based on one dimensional (1D) nanostructures for analysis of bioaffinity interactions]

It was shown that modification of screen printed graphite electrodes with gold nanoparticles (AuNPs) decorated Pb nanowires (PbNWs) demonstrates the enhancement of sensor's analytical characteristics such as effective surface area, electro catalytic properties and heterogeneous electron transfer kinetics. The reason for such improvement may be the synergistic effect ofAuNPs and PbNWs. Nanowires ensembles on electrode surface were employed for the detection of hemeproteins cytochrome P450 2B4, cytochrome c, and cardiac myoglobin in human plasma. Composite materials based on nanoparticles with different dimentions (3D three dimensional gold nanoparticles and 1D one dimensional Pb nanowires make it possible to construct biosensors with low detection limit of proteins.

Direct genotyping of Cytochrome P450 2A6 whole gene deletion from human blood samples by the SmartAmp method

BACKGROUND

Genetic polymorphisms of the human CYP2A6 gene are considered to be a determinant of smoking behavior and tobacco-related lung cancer risk in male Japanese smokers. We developed a SmartAmp-based genotyping method to detect whole deletion of the CYP2A6 gene directly from blood samples without DNA isolation.

METHODS

We validated the new method using CYP2A plasmids, 48 genomic DNA samples and 25 blood samples by utilizing the SmartAmp method, a unique isothermal DNA amplification process.

RESULTS

This method could discriminate the CYP2A6 gene from highly homologous CYP2A7 and CYP2A13 genes. CYP2A6*1 (wild-type) and CYP2A6*4 (whole gene deletion) were determined by the new method in perfect accordance with sequence analysis data.

CONCLUSIONS

A SmartAmp assay for genotyping the CYP2A6 gene was developed, and the reliability of the method was validated using the conventional PCR method.

Study of the pharmacokinetics and intragastric pH of rabeprazole given as successive intravenous infusion to healthy Chinese volunteers

OBJECTIVES

To investigate the pharmacokinetics and pharmacodynamics of rabeprazole (RPZ) given as successive intravenous infusion to healthy Chinese volunteers.

METHODS

A total of 63 subjects (33 males and 30 females) were recruited at four research centers and given a 5-day therapeutic course of RPZ (10, 20, or 40 mg) administered as single daily doses during a 30-min period. Plasma concentrations were monitored by sampling at very short intervals for the first 330, 360, or 420 min post-RPZ administration. Intragastric pH was recorded 24 h post-RPZ administration on day 1 and day 5.

RESULTS

After receiving a single and repeated doses of RPZ, the area under the plasma concentration-time curve (AUC(0-τ)) was 51.9 ± 22.1, 96.7 ± 27.6, and 188.4 ± 65.8 mg·min/L on day 1 and 59.3 ± 23.9, 106.7 ± 27.8, and 200.3 ± 79.0 mg·min/L on day 5 for the low-, middle-, and high-dose groups, respectively. The corresponding peak concentrations (C(max)) were 0.64 ± 0.11, 1.30 ± 0.26, and 2.6 ± 0.54 μg/mL on day 1 and 0.76 ± 0.15, 1.39 ± 0.25, and 2.91 ± 0.53 μg/mL on day 5, respectively. Although the mean AUC and C(max) values increased from a single dose to repeated doses in the three groups, the difference was not significant. The mean AUC((0, τ)) and C(max) ratios of repeated dose to single dose were 1.14, 1.10, and 1.06 on day 1 and 1.19, 1.07, and 1.12 on day 5 for the low-, middle-, and high-dose groups, respectively. After administration of a single dose, the 24-h pH value was significantly higher in the high-dose group than in the low-dose group. After repeated doses, significant increases in pH were observed in the low-, middle-, and high-dose groups; however, the between-group differences were not statistically significant.

CONCLUSIONS

There is a relationship between the pharmacokinetics and pharmacodynamics of RPZ, with the latter depending in part on the duration of administration, as evidenced by a higher AUC or C(max) and intragastric pH from repeated dosing.

CYP2A6 allele frequencies in an Iranian population

BACKGROUND

Genetic polymorphism of CYP2A6 gene is a major causal factor in the large interindividual differences in nicotine metabolism. It may have an impact on smoking behavior and smoke-related cancer susceptibility. Until now, there are no reports of CYP2A6 allele frequencies in Iranian population.

METHODS

In the present study, we investigated the frequencies of CYP2A6 alleles in 250 male Iranians. CYP2A6*2, CYP2A6*4, CYP2A6*9, and CYP2A6*12 were determined by allele-specific polymerase chain reaction.

RESULTS

Frequencies of *2, *4, *9, and *12 alleles were 2.2%, 0.95%, 12.4%, and 1.34%, respectively.

CONCLUSION

These results showed that the distribution of CYP2A6 alleles in Iranian population was different from those reported previously for other ethnic groups. This highlights the importance of conducting further studies to investigate the implications on smoking dependence and cancer in Iranians.

CYP2A6 genotype, phenotype, and the use of nicotine metabolites as biomarkers during ad libitum smoking

CYP2A6 inactivates nicotine to cotinine and cotinine to 3-hydroxycotinine. We investigated which of plasma nicotine and metabolites were most related to CYP2A6 genotype and smoking levels. We assessed demographic and smoking histories in 152 Caucasian ad libitum smokers, measured breath carbon monoxide (CO) levels, and determined plasma nicotine, cotinine, and 3-hydroxycotinine by high-performance liquid chromatography and CYP2A6 genotypes by PCR. Cigarettes per day was most closely related to CO (r = 0.60, P < 0.001) followed by plasma cotinine (r = 0.53, P < 0.001), whereas plasma cotinine was most strongly correlated with CO levels (r = 0.74, P < 0.001), confirming that cotinine is a good indicator of smoking levels; this was not limited by CYP2A6 variants. 3-Hydroxycotinine/cotinine is reported to be a good marker of CYP2A6 activity, and we found that the 3-hydroxycotinine/(cotinine + nicotine) ratio was most correlated with CYP2A6 genotype (r = 0.38, P < 0.001). Inclusion of the CYP2A6*12A allele strengthened the correlation (r = 0.46, P < 0.001), suggesting that the identification of novel alleles will continue to improve this relationship. Nicotine metabolism is slower in smokers, and we have shown that CYP2A6 is reduced by nicotine treatment in monkeys. Here, we found that plasma nicotine levels were inversely correlated with CYP2A6 activity (3-hydroxycotinine/cotinine, r = -0.41, P < 0.001) among those without CYP2A6 variants, suggesting a reduction in metabolism with higher nicotine levels. Together, these findings (a) confirm the use of plasma cotinine and CO as indicators of Caucasians' smoking levels, and that this is not limited by CYP2A6 genetic variation; (b) indicate that 3-hydroxycotinine/cotinine and 3-hydroxycotinine/(cotinine + nicotine) are moderately good indicators of the CYP2A6 genotype; and (c) support that nicotine exposure may reduce its own metabolism.

Contribution of CYP2C9 to variability in vitamin K antagonist metabolism

CYP2C9 is the third most important cytochrome P450 (CYP) in terms of number of drugs metabolised. A considerable amount of information on this isoform is now available with respect to its structural biology, the mechanisms by which it can be induced and the existence of a range of variant alleles, which are often functionally significant. CYP2C9 makes a very important contribution to metabolism of vitamin K antagonist anticoagulants, and is the main oxidising enzyme for S-warfarin and S-acenocoumarol as well as contributing to phenprocoumon metabolism. A large number of studies have now shown that CYP2C9 genotype predicts dose requirement for both warfarin and acenocoumarol, with a possible contribution for phenprocoumon. Patients with variant alleles are likely to require a lower dose and may be at risk of overcoagulation and resultant bleeding, especially during the induction phase of therapy. Although CYP2C9 genotype is clearly a predictor of vitamin K antagonist dose requirement, especially in Caucasian populations in whom variant alleles are common, a number of recent studies have shown that age, genotype for the gene encoding the target gene vitamin K epoxide reductase and concomitant drugs are equally important factors in determining dose. There is a need for prospective studies to assess the value of predicting dose requirement on the basis of all these factors, including the CYP2C9 genotype.

The pharmacokinetics of escitalopram in patients with hepatic impairment

The effect of hepatic impairment on the pharmacokinetics of escitalopram was determined by means of nonlinear mixed effect modeling, considering both the Child-Pugh classification (and its components) and cytochrome P450 2C19 (CYP2C19) activity. Twenty-four subjects were grouped according to their Child-Pugh score as healthy, with mild hepatic impairment or with moderate hepatic impairment. The subjects were administered a single oral dose of escitalopram 20 mg, and blood was sampled up to 168 hours after dosage. The serum concentration of escitalopram was determined and the pharmacokinetics assessed by nonlinear mixed effect modeling. The CYP2C19 activity was measured from the urinary excretion ratio of S/R-mephenytoin. All subjects tolerated the treatment well, and no serious adverse events were reported. Predicted mean area under the curve from zero to infinity (AUC(inf)) values were 51% and 69% higher for patients with mild and moderate hepatic impairment (Child-Pugh classification), respectively, compared with healthy subjects. The best-fitting model showed an influence of CYP2C19 activity on clearance and body weight on the volume of distribution for escitalopram. CYP2C19 activity is a better predictor of escitalopram clearance than is Child-Pugh classification.

Increased cytochrome P4501B1 gene expression in peripheral leukocytes of municipal waste incinerator workers

Incinerator workers are exposed to polycyclic aromatic hydrocarbons (PAHs) and dioxins in workplace. Previous studies indicated that aryl hydrocarbon receptor activation, following by increased cytochrome P4501A1 (CYP1A1) and 1B1 (CYP1B1) activity and expressions, was required for PAHs and dioxin induced toxicities. This study investigated whether municipal waste incinerator workers with frequent exposure to PAHs/dioxins in fly/bottom ash had increased CYP1A1 and CYP1B1 expressions in peripheral leukocytes and assessed whether CYP1B1*3 polymorphism modified the association between PAHs/dioxins exposure and CYP1B1 expressions. Based on job contents and time-activity profiles, 112 workers were classified into high exposure, medium exposure and control groups. CYP1A1 and CYP1B1 gene expressions in workers' leukocytes were determined with the real-time reverse transcriptase polymerase chain reaction method. After taking into account age, gender and smoking in the multiple regression analyses, CYP1B1, but not CYP1A1, levels were significantly higher in the high and medium exposure groups than in the control group, and there was a statistically significant interaction between exposure group and CYP1B1 genotype. These results suggested that CYP1B1 gene expression could be a potential biomarker of biologically effective dose for occupational exposure to PAHs/dioxins and CYP1B1*3 polymorphism modified effects of occupational exposures on CYP1B1 expression.

Pharmacogenetics and herb???drug interactions

OBJECTIVE

Ginkgo biloba was found to exert a significant inductive effect on CYP2C19 activity. This study was designed to investigate the potential herb-drug interaction between G. biloba and omeprazole, a widely used CYP2C19 substrate, in subjects with different CYP2C19 genotypes.

METHODS

Eighteen healthy Chinese subjects previously genotyped for CYP2C19 were selected. All subjects received a single omeprazole 40 mg at baseline and then at the end of a 12-day treatment period with G. biloba (140 mg, bid). Multiple blood samples were collected over 12 h, and 24 h urine was collected post omeprazole dosing. Plasma and urine concentrations of omeprazole and its metabolites, 5-hydroxyomeprazole and omeprazole sulfone, were determined, and their pharmacokinetics calculated non-compartmentally.

RESULTS

Plasma concentrations of omeprazole and omeprazole sulfone were significantly decreased, and 5-hydroxyomeprazole significantly increased following G. biloba administration in comparison to baseline. A significant decrease in the ratio of area under the plasma concentration-time curve (AUC) of omeprazole to 5-hydroxyomeprazole was observed in the homozygous extensive metabolizers, heterozygous extensive metabolizers, and poor metabolizers, respectively. The decrease was greater in PMs than EMs. No significant changes in the AUC ratios of omeprazole to omeprazole sulfone were observed. Renal clearance of 5-hydroxyomeprazole was significantly decreased after G. biloba, but the change was not significantly different among the three genotype groups.

CONCLUSION

Our results show that G biloba can induce omeprazole hydroxylation in a CYP2C19 genotype-dependent manner and concurrently reduce the renal clearance of 5-hydroxyomeprazole. Co-administration of G. biloba with omeprazole or other CYP2C19 substrates may significantly reduce their effect, but further studies are warranted.

St John's wort induces both cytochrome P450 3A4-catalyzed sulfoxidation and 2C19-dependent hydroxylation of omeprazole

OBJECTIVE

St John's wort, an extract of the medicinal plant Hypericum perforatum, is widely used as an herbal antidepressant. Although the ability of St John's wort to induce cytochrome P450 (CYP) 3A4-mediated reaction has been well established, the effect on CYP2C19 is still not determined. Thus the objective of this study was to determine the impact of St John's wort on the pharmacokinetic profiles of omeprazole and its metabolites.

METHODS

Twelve healthy adult men (6 CYP2C19*1/CYP2C19*1, 4 CYP2C19*2/CYP2C19*2 and 2 CYP2C19*2/CYP2C19*3) were enrolled in a 2-phase randomized crossover design. In each phase the volunteers received placebo or a 300-mg St John's wort tablet 3 times daily for 14 days. Then all subjects took a 20-mg omeprazole capsule orally. Blood samples were collected up to 12 hours after omeprazole administration. Omeprazole and its metabolites were quantified by use of HPLC with ultraviolet detection.

RESULTS

Omeprazole and its metabolites all exhibit CYP2C19 genotype-dependent pharmacokinetic profiles. After a 14-day treatment with St John's wort, substantial decreases in plasma concentrations of omeprazole were observed. The peak plasma concentration (C(max)) significantly decreased by 37.5% +/- 13.3% (P =.001) in CYP2C19*2/CYP2C19*2 or *3 and by 49.6% +/- 20.7% (P =.017) in CYP2C19*1/CYP2C19*1; the area under the concentration-time curve extrapolated to infinity [AUC(0- infinity )] decreased by 37.9% +/- 21.3% (P =.014) and 43.9% +/- 23.7% (P =.011) in CYP2C19 mutant and wild genotypes, respectively. Moreover, the C(max) and AUC(0- infinity ) of omeprazole sulfone increased by 160.3% +/- 45.5% (P =.001) and by 136.6% +/- 84.6% (P =.014), 155.5% +/- 58.8% (P =.001), and 158.7% +/- 101.4% (P =.017) in mutant and wild genotypes, respectively. St John's wort increased the C(max) of 5-hydroxyomeprazole by 38.1% +/- 30.5% (P =.028) and the AUC(0- infinity ) by 37.2% +/- 26% (P =.005) in CYP2C19 wild-type subjects, whereas it did not produce any significant alterations to the corresponding pharmacokinetic parameters in subjects with variant genotypes.

CONCLUSION

St John's wort induces both CYP3A4-catalyzed sulfoxidation and CYP2C19-dependent hydroxylation of omeprazole and enormously decreases the plasma concentrations of omeprazole. Clinically relevant interactions with other drugs may occur and must be taken into account when St John's wort is being taken.

Enantioselective Analysis of Citalopram and its Metabolites in Postmortem Blood and Genotyping For CYD2D6 and CYP2C19

Citalopram, a selective serotonin reuptake inhibitor, is one of the most commonly found drugs in Swedish forensic autopsy cases. Citalopram is a racemic drug with 50:50 of the S- and R- enantiomers. Enantioselective analysis of citalopram and its metabolites desmethylcitalopram and didesmethylcitalopram were performed in femoral blood from 53 autopsy cases by a chiral high-performance liquid chromatography (HPLC) method. The mean (+/- standard deviation) S/R ratio for citalopram was 0.67 +/- 0.25 and for desmethylcitalopram, 0.68 +/- 0.20. We found increasing S/R ratios with increasing concentrations of citalopram. We also found that high citalopram S/R ratios were associated with a high parent drug-to-metabolite ratio and may be an indicator of recent intake. Citalopram is metabolized by cytochrome P450 (CYP) 3A4, 2C19, and 2D6. Genotyping for the polymorphic CYP2C19 and CYP2D6 revealed no poor metabolizers regarding CYP2C19 and only 2 (3.8%) poor metabolizers regarding CYP2D6. The presence of drugs metabolized by and/or inhibiting these enzymes in several of the cases suggests that such pharmacokinetic interactions are a more important (practical) problem than metabolic deficiency. Enantioselective analysis of citalopram and its metabolites can provide additional information when interpreting forensic toxicology results and might be a necessity in the future.

Association of CYP17, CYP19, CYP1B1, and COMT Polymorphisms with Serum and Urinary Sex Hormone Concentrations in Postmenopausal Women

Women with high circulating estrogen concentrations have an increased risk of breast cancer; thus, it is important to understand factors, including genetic variability, that influence estrogen concentrations. Several genetic polymorphisms that may influence sex hormone concentrations have been identified, including CYP17 (5'-untranslated region T-->C), CYP19 [intron 4 (TTTA)(n = 7-13) and a 3-bp deletion (-3)], CYP1B1 (Val(432)Leu), and COMT (Val(108/158)Met). We examined associations between these polymorphisms and serum concentrations of estrogens, androgens, and sex hormone-binding globulin and urinary concentrations of 2- and 16alpha-hydroxyestrone in 171 postmenopausal women, using data from the prerandomization visit of an exercise clinical trial. Participants were sedentary, not taking hormone therapy, and had a body mass index >24.0. Compared with noncarriers, women carrying two CYP19 7r(-3) alleles had 26% lower estrone (P < 0.001), 19% lower estradiol (P = 0.01), 23% lower free estradiol (P = 0.01), and 22% higher sex hormone-binding globulin concentrations (P = 0.06). Compared with noncarriers, women carrying at least one CYP19 8r allele had 20% higher estrone (P = 0.003), 18% higher estradiol (P = 0.02), and 21% higher free estradiol concentrations (P = 0.01). Women with the COMT Met/Met genotype had 28% higher 2-hydroxyestrone (P = 0.08) and 31% higher 16alpha-hydroxyestrone concentrations (P = 0.02), compared with Val/Val women. Few associations were found for CYP17 and CYP1B1 or with serum androgen concentrations. This study provides further evidence that genetic variation may appreciably alter sex hormone concentrations in postmenopausal women not taking hormone therapy.

Population pharmacokinetics and metabolism of midazolam in pediatric intensive care patients

OBJECTIVE

To determine the pharmacokinetics and metabolism of midazolam in pediatric intensive care patients.

DESIGN

Prospective population pharmacokinetic study.

SETTING

Pediatric intensive care unit.

PATIENTS

Twenty-one pediatric intensive care patients aged between 2 days and 17 yrs.

INTERVENTIONS

The pharmacokinetics of midazolam and metabolites were determined during and after a continuous infusion of midazolam (0.05-0.4 mg/kg/hr) for 3.8 hrs to 25 days administered for conscious sedation.

MEASUREMENTS AND MAIN RESULTS

Blood samples were taken at different times during and after midazolam infusion for determination of midazolam, 1-OH-midazolam, and 1-OH-midazolam-glucuronide concentrations via high-performance liquid chromatography-ultraviolet detection. A population analysis was conducted via a two-compartment pharmacokinetic model by the NPEM program. The final population model was used to generate individual Bayesian posterior pharmacokinetic parameter estimates. Total body clearance, apparent volume distribution in terminal phase, and plasma elimination half-life were (mean +/- sd, n = 18): 5.0 +/- 3.9 mL/kg/min, 1.7 +/- 1.1 L/kg, and 5.5 +/- 3.5 hrs, respectively. The mean 1-OH-midazolam/midazolam ratio and (1-OH-midazolam + 1-OH-midazolam-glucuronide)/midazolam ratio were 0.14 +/- 0.21 and 1.4 +/- 1.1, respectively. Data from three patients with renal failure, hepatic failure, and concomitant erythromycin-fentanyl therapy were excluded from the final pharmacokinetic analysis.

CONCLUSIONS

We describe population and individual midazolam pharmacokinetic parameter estimates in pediatric intensive care patients by using a population modeling approach. Lower midazolam elimination was observed in comparison to other studies in pediatric intensive care patients, probably as a result of differences in study design and patient differences such as age and disease state. Covariates such as renal failure, hepatic failure, and concomitant administration of CYP3A inhibitors are important predictors of altered midazolam and metabolite pharmacokinetics in pediatric intensive care patients. The derived population model can be useful for future dose optimization and Bayesian individualization.

Contributions of CYP2D6, CYP2C9 and CYP2C19 to the biotransformation of E- and Z-doxepin in healthy volunteers

In-vitro data indicated a contribution of cytochrome P450 enzymes 1A2, 3A4, 2C9, 2C19 and 2D6 to biotransformation of doxepin. We studied the effects of genetic polymorphisms in CYP2D6, CYP2C9 and CYP2C19 on E- and Z-doxepin pharmacokinetics in humans. Doxepin kinetics was studied after a single oral dose of 75 mg in healthy volunteers genotyped as extensive (EM), intermediate (IM) and poor (PM) metabolizers of substrates of CYP2D6 and of CYP2C19 and as slow metabolizers with the CYP2C9 genotype *3/*3. E-, Z-doxepin and -desmethyldoxepin were quantified in plasma by HPLC. Data were analyzed by non-parametric pharmacokinetics and statistics and by population pharmacokinetic modeling considering effects of genotype on clearance and bioavailability. Mean E-doxepin clearance (95% confidence interval) was 406 (390-445), 247 (241-271), and 127 (124-139) l h(-1) in EMs, IMs and PMs of CYP2D6. In addition, EMs had about 2-fold lower bioavailability compared with PMs indicating significant contribution of CYP2D6 to E-doxepin first-pass metabolism. E-doxepin oral clearance was also significantly lower in carriers of CYP2C9*3/*3 (238 l h(-1) ). CYP2C19 was involved in Z-doxepin metabolism with 2.5-fold differences in oral clearances (73 l h(-1) in CYP2C19 PMs compared with 191 l h(-1) in EMs). The area under the curve (0-48 h) of the active metabolite -desmethyldoxepin was dependent on CYP2D6 genotype with a median of 5.28, 1.35, and 1.28 nmol l h(-1) in PMs, IMs, and EMs of CYP2D6. The genetically polymorphic enzymes exhibited highly stereoselective effects on doxepin biotransformation in humans. The CYP2D6 polymorphism had a major impact on E-doxepin pharmacokinetics and CYP2D6 PMs might be at an elevated risk for adverse drug effects when treated with common recommended doses.

Effects of whole deletion of CYP2A6 on nicotine metabolism in humans

We investigated the effects of CYP2A6 genotypes on nicotine metabolism, focused from nicotine to cotinine and its additional 3'-hydroxylating resulted in trans-3'-hydroxycotinine formation. In the subjects genotyped by PCR-RFLP method, one cigarette smoking experiment was performed and urine samples were collected for 24 h. In all subjects who smoked, we detected nicotine, cotinine and trans-3'-hydroxycotinine in urine by GC-MS analysis. In whole deletion of CYP2A6, urinary excretion amounts of cotinine and trans-3'-hydroxycotinine were significantly smaller than those in the wild-type of CYP2A6*1. A lack of CYP2A6 reduces the formation of cotinine and trans-3'-hydroxycotinine, but not entirely reduces the trans-3'-hydroxycotinine formation. Unknown cotinine 3'-hydroxylating activity except CYP2A6 are suspected in humans.

[Applications of aryl hydrocarbon hydroxylase in diagnosis of lung cancer]

OBJECTIVE

To develop a new biomarker and improve early diagnosis of lung cancer in clinic.

METHODS

Aryl hydrocarbon hydroxylase (AHH) activity in peripheral lymphocytes was detected using spectrofluorometer in 51 healthy subjects, 30 patients with benign lung diseases, 93 patients with lung cancer (including 30 patients with lung adenocarcinoma, 30 with lung squamous carcinoma, 33 with small cell lung cancer, 28 of them were at I, II stage, 35 at III stage, 30 at IV stage), and the results were compared with carcinoembryonic antigen(CEA).

RESULTS

AHH activity in peripheral lymphocytes was (4.9 +/- 2.1) pmol.min-1 x 10(-6) cells in patients with lung cancer, (7.3 +/- 1.9) pmol.min-1 x 10(-6) cells in patients with lung squamous carcinoma, (1.1 +/- 0.7) and (1.2 +/- 0.6) pmol.min-1 x 10(-6) cells in healthy subjects and patients with benign lung diseases respectively. It is indicated that AHH activity in peripheral lymphocytes was significantly increased in patients with lung cancer, especially with lung squamous cancer. Of patients with lung cancer, AHH activity was (3.7 +/- 1.4) pmol.min-1 x 10(-6) cells in patient at stage I, II, (5.1 +/- 2.1), (7.1 +/- 1.8) pmol.min-1 x 10(-6) cells at stage III and stage IV, and AHH activity increased when patients deteriorated, vice versa. Diagnosis evaluation test indicated that AHH was over 80% in both sensitivity and specificity. AHH relative risk to lung cancer was 2.83.

CONCLUSIONS

AHH is a promising marker of lung cancer which is special for lung squamous carcinoma, it can be used in clinical diagnosis, mornitoring and prognosis estimating in patients with lung cancer.

Lymphocyte esterases and hydroxylases in neurotoxicology

Certain human lymphocytic enzymes, such as neuropathy target esterase (NTE), have become useful markers in clinical toxicology. NTE has been proposed as a predictive marker in organophosphate poisoning for the subsequent development of organophosphate-induced delayed neuropathy. We studied lymphocyte aryl hydrocarbon hydroxylases, and using a differential method based on that of NTE employing a phenyl-alkanoic substrate, developed an enzyme assay for use in toxic neuropathies. The assayed enzyme, which we refer to as neuropathy target hydroxylase (NTH), performed similarly to NTE in the evaluation of coherent clinical data obtained in patients with toxic neuropathies. This study indicates good correlation between the severity of clinical illness and abnormally low levels of NTH in neuropathies of varied etiology. A simplified protocol for NTH assay is presented.

Age, smoking and the activity of the mono-oxygenase aryl hydrocarbon hydroxylase in isolated human peripheral blood monocytes

Age-associated changes in the microsomal mono-oxygenase enzyme, aryl hydrocarbon hydroxylase (AHH), were investigated in peripheral blood monocytes isolated from young and elderly subjects. Young subjects were selected from the age group < 35 years; elderly subjects were > 70 years. AHH activity, expressed as nM 3-hydroxy benzopyrene formed/10(6) cells/h of incubation, was similar in young and elderly non-smokers (elderly = 6.7 +/- 1.8; young = 9.1 +/- 0.9; p > 0.05). In smokers, contrary to some previous reports, AHH activity was not significantly higher than in non-smokers of similar age (elderly smokers = 8.6 +/- 1.0; young smokers = 10.5 +/- 2.4; p > 0.05). There was no significant difference between young and elderly smokers (p > 0.05). We conclude that: (a) AHH activity is similar in young and old non-smoking individuals; (b) no significant differences were detected in in vivo induction of this enzyme activity between smokers and non-smokers.

Better perspectives on use of biological markers in monitoring of lung cancer risk in occupational settings

Although conventional approaches in cancer epidemiology and prevention have provided a wealth of information, they are seriously limited in their ability to detect and evaluate carcinogenic hazards. However, traditional methods combined with newly developed laboratory procedures provide biological markers of molecular or biochemical events linked to carcinogen exposure and open a new approach to the study of human cancer risk assessment. The goal of the new approach is to identify as precisely as possible specific carcinogenic hazards in the environment, to assess their biologically effective dose and biological effect, and to provide a means of appraising host factors that modify susceptibility. A particular promising new tool of cancer risk assessment is the highly sensitive immunoassay for carcinogen-DNA adducts. These assays may provide a tissue dosimeter of carcinogen exposure. In this paper research studies were mentioned that aimed at assessing the levels of benzo[a]pyrene-DNA adducts and protein adducts, utilizing white blood cells, or tissue specimens obtained from tissue biopsy or autopsy. Another promising method in discovering BAP exposure are levels of carcinogen-metabolizing enzymes. The potential significance in surveillance and monitoring of aryl-hydrocarbon hydroxylase (AHH) has been discussed.

Effect of aging and other factors on monocyte aryl hydrocarbon hydroxylase activity

A measure of the activity of macrophage drug metabolizing enzymes through assay of peripheral monocytes was used to assess the hepatic enzymatic status and thereby evaluate age related changes in drug metabolism. Blood was obtained from elderly subjects (aged 74.8 +/- 5.2, mean +/- S.E., n = 16) and a young control group (aged 23.5 +/- 2.0, n = 27). Monocyte AHH activity was used as an index of liver drug metabolism, ALT activity as an index of liver function, monocyte media IL-1 and as an index of macrophage activation and serum IL-1 levels as a measure of endogenous pyrogenic activity. The medium collected from the cultured monocytes was also assessed for the presence of AHH inhibitory activity. Subjects provided information relating to their age, sex, alcohol consumption, cigarette smoking, recent infection, recent surgery, disease status and medications which could alter drug metabolism. Elderly patients were drawn both from independent seniors living at home and seniors visiting a geriatric day hospital and compared to a control group of young healthy volunteers. Using the experimental design AHH activity did not differ within experimental error between aged (0.832 +/- 0.32 nmol/mg prot. per h, n = 16) and young control subjects (0.452 +/- 0.17, n = 27). ALT activity did not differ between aged (2.83 I.U. +/- 0.46) and young (4.24 +/- 0.82). Monocyte AHH activity did not differ between males (0.45 +/- 0.14, n = 33) compared to females (0.65 +/- 0.18, n = 29), but was significantly higher in smokers (2.5 +/- 1.0, n = 5) compared to non-smokers (0.35 +/- 0.05, n = 52). Mild to moderate alcohol use showed no significant effect on AHH activity. There was no significant difference between the mean level of MCM inhibition of murine hepatocyte AHH between elderly (44.3 +/- 8.32%, n = 8) and control (31.5 +/- 6.21%, n = 15) subjects, but a larger proportion of the elderly population demonstrated such an effect. Serum IL-1 levels (range 0-55.9 pg/ml) were compared to MCM IL-1 and AHH inhibitory activity in the elderly and young group.

Monocyte arylhydrocarbon hydroxylase activity and mortality

Monocyte arylhydrocarbon hydroxylase (AHH) activity is decreased in patients with liver disease and correlates with severity of disease. Patients with chronic liver disease (n = 34) were studied to determine if decreased monocyte AHH activity is associated with mortality. Monocyte AHH activity in the nonsurvivor group was 0.07 +/- 0.025 nmol/mgP/h (n = 11) and was significantly lower than the survivor group 0.198 +/- 0.031 (n = 23). Both groups were significantly lower than controls 0.41 +/- 0.053 (n = 19). Of the liver function tests, only serum albumin was different between the survivor group and the nonsurvivor group. Patients in the nonsurvivor group had significantly higher Child-Turcotte scores than the survivor group. These results suggest that the monocyte AHH activity may be a good index of survival in patients with liver disease, but the high degree of overlap between survivors and nonsurvivors suggests otherwise.

[AHH activity and life environmental factors]

To investigate life environmental factors which affect aryl hydrocarbon hydroxylase (AHH) activity, basal and 3-methylcholanthrene(3-MC)-induced AHH activities were determined by the formation of 3-hydroxybenzo(a)pyrene in cultured lymphocytes obtained from 111 healthy male subjects who lived in Fukuoka Prefecture, Japan. Fold induction (3-MC-induced/basal) was calculated. Relationship between the absolute activities and the fold induction of AHH and life environmental factors was statistically examined. Study of simple correlation indicated the following: Basal AHH activity was positively correlated with age and habitual intake of drugs. Induced AHH activity was positively correlated with coffee intake, smoking and habitual intake of drugs. Fold induction was positively correlated with coffee intake and smoking, and negatively with age. Using multiple regression analysis, habitual intake of drugs showed positive relation to both basal and induced enzyme activity, and age showed positive relation to the basal activity and negative relation to the fold induction.

Depression of peripheral blood monocyte aryl hydrocarbon hydroxylase activity in patients with liver disease: possible involvement of macrophage factors

Aryl hydrocarbon hydroxylase activity was detectable in cultured macrophage monolayers of peripheral blood monocyte origin. Peripheral blood monocytes were isolated from patients with biopsy-confirmed liver disease and healthy volunteers. Macrophage monolayers were prepared and incubated at 37 degrees C. After 24 hr, the aryl hydrocarbon hydroxylase activity and cellular protein concentration were assayed on cell homogenates. The monocyte aryl hydrocarbon hydroxylase activity in cultured macrophages from normal volunteers was 1.23 +/- 0.16 (n = 19). The aryl hydrocarbon hydroxylase activity in macrophage cultures from patients with biopsy-confirmed liver disease was 0.48 +/- 0.05 (n = 20). This represents a significant (61%) decrease in monocyte aryl hydrocarbon hydroxylase compared to controls. The 20 patients have established cirrhosis or early stage liver disease. The established cirrhosis group includes alpha 1-antitrypsin deficiency-associated cirrhosis; primary biliary cirrhosis; alcoholic (Laennec's) cirrhosis; cryptogenic cirrhosis, and hemochromatosis. Early stage liver disease is attributed to methotrexate (Stage III), early stage primary biliary cirrhosis and alpha 1-antitrypsin deficiency. Our results indicate that the depression in monocyte aryl hydrocarbon hydroxylase activity is greater in patients with established cirrhosis than early stage liver disease. Our results further suggest that cultured monocytes from patients with liver disease spontaneously release soluble factors into the culture medium. Incubation of this medium, containing macrophage factors, with isolated hepatocytes significantly depress hepatocyte aryl hydrocarbon hydroxylase activity compared to medium obtained from cultures of monocytes from normal volunteers.(ABSTRACT TRUNCATED AT 250 WORDS)

[Smoking and induction of the enzyme aryl hydrocarbon hydroxylase in patients with laryngeal carcinomas and precancerous conditions]

The risk for a smoker of developing cancer of the larynx depends on the activity of the enzyme arylhydroxcarbonhydroxylase in his cells. The higher the genetically determined arylhydroxcarbonhydroxylase activity, the higher is the probability of developing the disease.

Monooxygenase activity of human hemoglobin: role of quaternary structure in the preponderant activity of the beta subunits within the tetramer

Catalysis of para hydroxylation of aniline was measured for human ferrihemoglobin and various derivatives in a reconstituted system consisting of the appropriate hemoprotein (at 4 microM heme), reduced nicotinamide adenine dinucleotide phosphate (NADPH), cytochrome P-450 reductase, and aniline under atmospheric O2. The isolated subunits of hemoglobin (alpha 3+ and beta 3+4) were prepared by treatment with p-(hydroxymercuri)benzoate. Semihemoglobin (alpha heme2 beta 02) was prepared from ferrihemoglobin and apohemoglobin. Converse valency hybrids alpha 3+2(beta 2+-CO)2 and (alpha 2+-CO)2 beta 3+2 were prepared from appropriately ligated alpha and beta subunits. After chromatography, the hemoglobin derivatives were characterized by visible and 1H NMR spectroscopy and electrophoresis. At the same concentration of aniline, the alpha and beta subunits were much less active than the normal tetramer. alpha-Semihemoglobin and the alpha 3+2(beta 2+-CO)2 hybrid also displayed lower hydroxylase activity. The (alpha 2+-CO)2 beta 3+2 hybrid was about as active as normal alpha 3+2 beta 3+2. This result suggests that the activity of tetrameric hemoglobin primarily involves the beta subunits. Also transfer of the beta subunits from the beta 4 molecular environment to the alpha 2 beta 2 state enhances their monooxygenase activity approximately 15-fold. The hemoglobin derivatives were differently susceptible to substrate inhibition, the beta 4 species being most sensitive. Estimates of Vmax from the linear portions of the corresponding Lineweaver-Burk plots showed agreement within a factor of 2.5 for all of the hemoglobin derivatives, suggesting that the intrinsic O2-activating capacities of the derivatives are similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Monooxygenase activity of human hemoglobin: NMR demonstration of different modes of substrate binding corresponding to different activities of hemoglobin derivatives

In the accompanying paper [Ferraiolo, B. L., Onady, G. M., & Mieyal, J. J. (1984) Biochemistry (preceding paper in this issue)] we reported different aniline hydroxylase activities for ferrihemoglobin, its isolated subunits, and the converse pair of valency hybrids alpha 3+2(beta 2+-CO)2 and (alpha 2+-CO)2 beta 3+2 in a reconstituted system containing reduced nicotinamide adenine dinucleotide phosphate (NADPH) and cytochrome P-450 reductase. To investigate the molecular basis for the different activities, 1H NMR T1 relaxation studies of aniline were performed in the absence and presence of each of the hemoglobin (Hb) species. The paramagnetic contribution of the ferric heme iron atoms of each Hb derivative to the enhanced relaxation of the proton nuclei of aniline was determined relative to control experiments in which the hemoproteins had been converted fully to the corresponding (carbonmonoxy)ferrous forms, which are diamagnetic. According to the known distance dependence of the paramagnetic effect and the relative changes in T1 for the upfield and downfield signals in the spectrum of aniline, it was ascertained that aniline binds in the same manner to the beta-ferric hybrid and to ferrihemoglobin. These two forms displayed equivalent hydroxylase activities that were the highest among the Hb derivatives for the same aniline concentration. The T1 changes observed with the alpha-ferric hybrid suggest a different orientation for aniline in that complex. The T1 data for the isolated subunits alpha 3+ and beta 3+4 would indicate that overall binding of aniline includes a component of direct aniline-heme ligation in each case.(ABSTRACT TRUNCATED AT 250 WORDS)

Aryl hydrocarbon hydroxylase induction levels in patients with malignant tumors associated with smoking

The levels of aryl hydrocarbon hydroxylase (AHH) inducibility were assessed in 173 patients with cancers statistically associated with smoking, i.e., squamous cell and transitional cell carcinomas, at various sites. In 34 patients with carcinomas of the oral cavity, 41 patients with laryngeal carcinomas, and 22 patients with pulmonary carcinomas there was a highly significant overrepresentation of high inducers, whereas 30 patients with carcinomas of the renal pelvis and ureter and 46 patients with urinary bladder carcinomas did not differ significantly in this respect from a control population comprising 92 subjects with no history of neoplastic disease. The results add further support to the concept of AHH as a major activator of carcinogens belonging to the group of polycyclic aromatic hydrocarbons (PAH) when these affect the oral cavity and/or the respiratory tract. The role of AHH in urothelial carcinogenesis seems to be less explicit.

Alterations in leukocyte aryl hydrocarbon hydroxylase activity associated with treatment and age in psoriasis patients and healthy individuals

We have examined the relationship between topical psoriasis treatment and the activity of the mixed function oxidase, aryl hydrocarbon hydroxylase (AHH), in peripheral blood monocytes and lymphocytes from 20 patients with psoriasis. These data were compared to monocyte and lymphocyte AHH activity measured in 20 normal subjects. AHH activity was determined in cells induced with benzanthracene and in uninduced control cells. Monocyte and lymphocyte AHH activity in six untreated psoriasis patients was similar to that in the healthy controls. AHH activity in either uninduced or induced monocytes showed an increase with age in both the healthy and the untreated psoriatic subjects. Lymphocytes from the healthy subjects showed an age-related decline in enzyme activity. Fourteen patients with psoriasis receiving topical tar and/or topical corticosteroid therapy had significantly higher (P less than 0.05) levels of basal and induced monocyte and lymphocyte AHH activity than the healthy controls. AHH activity is age-related and appears to be controlled differently in monocytes and in lymphocytes. AHH activity in circulating monocytes and lymphocytes may be stimulated by topical tar and/or steroid therapy of psoriasis.

Blood monocyte aryl hydrocarbon hydroxylase activity in psoriasis

The activity of aryl hydrocarbon hydroxylase (AHH) in monocytes from 13 healthy control subjects and in 16 patients with discoid psoriasis was measured. The mean basal monocyte AHH activities of the control and psoriatic groups were 3.4 +/- 0.47 and 4.46 +/- 0.55 respectively (pmol 3-OHBP h-1 10(-6) cells). This difference was not significant. The mean induced monocyte AHH activities in the control and psoriatic groups were 56.4 +/- 10.8 and 77.8 +/- 16.0 pmol 3-OHBP h-1 10(-6) cells respectively but this difference was not significant. The mean induction ratios in the control and psoriatic groups were 16.5 +/- 1.8 and 20.4 +/- 3.6 respectively. Again, this difference was not significant. We conclude therefore, that monocyte aryl hydrocarbon hydroxylase activity is not reduced in psoriasis.

Aryl hydrocarbon hydroxylase activity in cultured lymphocytes of psoriatic patients

To evaluate further the metabolic capacity of psoriatics, the activities and inducibility of aryl hydrocarbon hydroxylase (AHH) were measured in cultured mitogen-stimulated lymphocytes from the peripheral blood of 68 psoriatic and 39 control patients. There was no significant difference in the mean basal and induced AHH activities between the psoriatics and the controls, although the former showed a slight tendency towards a higher inducibility ratio. In both, the basal and induced AHH values decreased significantly with increasing age. The cigarette smokers in both groups had significantly higher AHH activities than the nonsmokers. Antipsoriatic treatment (Anthralin, PUVA) did not seem to influence the lymphocyte AHH activities. No association was demonstrable between the AHH activities and the duration of the disease.

A method for detecting aryl hydrocarbon hydroxylase activities in cryopreserved human lymphocytes

Aryl hydrocarbon hydroxylase (AHH) activity, NADH-dependent cytochrome c reductase (cyt c) activity, and [3H]thymidine (3H-TdR) incorporation were monitored in human lymphocytes cryopreserved for periods up to 1 year. A standard procedure for freezing, thawing and culturing of these lymphocytes was developed. Kinetics for expression of benz[a]anthracene-(BA)-induced AHH activity, cyt c activity, and 3H-TdR incorporation were similar in both freshly cultured and cryopreserved cells. Lymphocyte samples from 10 individuals were collected once per month over a 3-month period and cells were either cultured at the time of donation or cryopreserved for later assay. Results indicated that the cryopreserved lymphocytes efficiently responded to mitogen activation. The intra-individual variation in AHH activities was reduced in the cryopreserved lymphocytes compared to the freshly cultured cells, and the relative ranking of these individuals in terms of their AHH activities remained constant for both fresh and cryopreserved samples. Cryopreservation seems to offer significant advantages over the freshly cultured lymphocytes because it allows for lymphocyte samples to be collected in diverse geological locations and over extended periods of time and yet permits for the culture and assay of all the cell samples at exactly the same time.

The effect of an individual's blood pressure on the percentage of total 7,12-dimethylbenz[a] anthracene metabolites that bind covalently to DNA in cultured resting lymphocytes

A method for the quantitative analysis of the percent metabolism that results in covalent binding of 7,12-dimethylbenz[a]anthracene (DMBA) to DNA in viable resting human lymphocytes is described. The inter- and intra-experimental reproducibility as judged by the coefficient of variation and examined in the same individual over a 3-month period was 31.4% and 13.9%, respectively. When the lymphocytes from 30 hypertensive individuals were exposed to 1 microM DMBA for 18 h, the percent of total DMBA metabolites that bind DNA covalently was correlated to the blood pressures of the patients at the time of sampling (r = 0.53, P less than 0.005). No influences on the data from the type or duration of hypertensive drug treatment could be statistically determined for this sample of hypertensive patients. It was concluded that high blood pressure is a strong determinant in predisposing lymphocytes to increased genetic risk from induced DNA damage and that this relationship is not statistically affected by hypertensive drug therapy.

Mixed function oxidase and glutathione S-transferase activities in normal human peripheral blood lymphocytes

The carcinogenic activity of some chemicals may be related to uncoupling of metabolism mediated by the mixed function oxygenase system. The intermediate formation of reactive epoxides or hydroxylamines may be eliminated by glutathione S-transferase. The ratio between these 2 enzymic activities may indicate if individuals are prone to cancerous development. If adequate cellular samples are available, assay of these enzymes may be used to trace individuals at risk. Therefore the present paper estimates these 2 enzymic activities (i.e., aryl hydrocarbon hydroxylase (AHH) and N-demethylation, the metabolite forming enzyme activities and glutathione S-transferase, the metabolite detoxifying enzymes), in the peripheral blood lymphocytes of 35 subjects. Their median age was 34 years. AHH activity was increased by 52% in the lymphocyte homogenate and by 45% in the microsomal fraction of smokers when compared with non-smokers. The enzyme activity also increased by 73% in the homogenate and by 93% in the microsomes of those taking drugs. The activity of N-demethylase increased by 212% in microsomes of smokers. However, the glutathione S-transferase activity decreased by about 2% in the lymphocyte homogenate and cytosol of smokers. The subjects taking drugs showed a decrease in this enzyme activity by 8% in the homogenate and by 37% in the cytosol.

High-pressure liquid chromatographic analysis of benzo(a)pyrene metabolism by human lymphocytes from donors of different aryl hydrocarbon hydroxylase inducibility and antipyrine half-lives

With high-pressure liquid chromatography (HPLC), lymphocytes from six human donors were evaluated for their ability to metabolize benzo(a)pyrene (BP). Donors whose aryl hydrocarbon hydroxylase (AHH) inducibility ratios ranged from 2.4 to 4.6 and whose antipyrine plasma half-lives ranged from 8 to 17 hr were examined. The BP metabolites identified were: 7,8-dihydrodiol, quinones, and 9-hydroxy and 3-hydroxy phenols. HPLC profiles of BP metabolites elaborated by uninduced (control) and benz(a)anthracene-induced lymphocytes were qualitatively similar among the six donors. A good correlation (r = 0.79) was found between known AHH inducibility ratios for the donors, as determined by the conventional fluorometric AHH assay, and induction of BP phenol production quantitated from HPLC data. HPLC results also indicated that the induction of benzo(a)pyrene-7,8-dihydrodiol, the proposed proximate carcinogenic form of BP, did not parallel BP phenol induction. Furthermore, the data also indicated a good negative correlation between AHH inducibility and the measurements of plasma antipyrine or urinary 4-hydroxyantipyrine half-lives (r = -0.88 or -0.91), respectively.

Effect of tumor promoters on induction of aryl hydrocarbon hydroxylase in human lymphocytes

The induction of aryl hydrocarbon hydroxylases in lymphocytes is dependent on their activation. The tumor-promoting phorbol esters which induce blast formation and DNA synthesis in lymphocytes enable polycyclic aromatic hydrocarbons to induce aryl hydrocarbon hydroxylases. Melittin, the major constituent of bee venom, acts synergistically with these phorbol esters in enhancing both lymphocyte activation and hydroxylase synthesis. Since aryl hydrocarbon hydroxylases convert procarcinogens to carcinogens these results suggest that tumor promotion by phorbol esters may be associated with their ability to affect the induction of these enzymes. This hypothesis is supported by the finding that phorbol and phorbol esters which lack tumor-promoting activity fail to enhance induction of aryl hydrocarbon hydroxylases in lymphocytes. However mezerein, although rather ineffective in promoting tumors, activates lymphocytes and permits polycyclic aromatic hydrocarbons to induce their hydroxylases effectively.

Induction of aryl hydrocarbon hydroxylase in human peripheral blood lymphocytes by chrysene

Many of the polycyclic aromatic hydrocarbons (e.g., benzo[a]pyrene (B[a]P), benzanthracene (BA), 3-methylcholanthrene (3-MC)) are not only carcinogenic, but also induce AHH in human tissues. Recently, chrysene has been implicated as an etiologic determinant of chemical carcinogenesis. Here we describe the ability of chrysene to induce AHH in cultured human lymphocytes. Lymphocytes were obtained from 9 healthy subjects, divided into 2 sets, and cultured in duplicate, triplicate, or quadruplicate for 48 h. Chrysene (25 microM final concentration) in acetone was then added to the induced culture set and the control set received acetone alone. Lymphocytes were then cultured an additional 24 h before harvesting. AHH was quantitated by a fluorometric analysis of the phenolic metabolites produced by incubating the lymphocytes with B[a]P for 35 min. A significant increase in enzyme induction occurred in the chrysene-induced cultures compared with control (non-induced) cells (one-tailed student t-test; P less than 0.001). It was also observed that the interindividual variation in AHH inducibility seen with other PAHs is also observed with chrysene.

Aryl hydrocarbon hydroxylase in persons with lung or laryngeal cancer

To test whether the distribution of AHH inducibility is shifted toward the high end of the range in patients who had lung and laryngeal cancer, we measured this trait in 59 patients (32 lung and 27 laryngeal) who had resectable tumors and had been disease-free for a period of time. The advantage of selecting patients who were free of clinical disease was that measurement of their AHH inducibility should not have been affected by the disease state. Patient and control populations showed no difference in basal and induced AHH activity of AHH inducibility. The mean AHH inducibility in patients who had lung cancer was 3.20 +/- 0.20; in patients who had laryngeal cancer 2.96 +/- 0.18, and for all controls 3.29 +/- 0.04 (no significant difference at p = 0 05). Further analysis of the distribution of AHH inducibility in the patient group compared to controls showed no suggestion of a shift toward the higher end of the range in patients who had lung and laryngeal cancer.

Aryl hydrocarbon hydroxylase in asbestos workers

Aryl hydrocarbon hydroxylase (AHH) activity and inducibility were studied in the lymphoblasts of 47 asbestos workers and 31 control subjects. Mean inducibility (3-methylcholanthrene [MC]-or dibenz(a,h,)anthracene [DBA]-induced divided by basal enzyme activity) was greater in the occupationally exposed subjects than in the control subjects. The estimated estimated change in mean value (+/- SE) of MC inducibility was 0.88 +/- 0.21 (P less than 0.001), and that of DBA inducibility was 1.59 +/- 0.56 (P less than 0.01). Differences in inducibility values were particularly apparent in 12 pairs of spouses, in all of whom the inducibility values of the occupationally exposed subjects exceeded those of their spouses. The differences in inducibility of AHH resulted from increases in induced activity, not from any appreciable change in basal activities. They were independent of subject age, sex, smoking status, year of first exposure to asbestos, yield of lymphoblasts, or the rate of blastogenesis as measured by the incorporation of tritiated thymidine into nucleic acid. Increased AHH inducibility may bear some relation to the greatly increased risk of bronchogenic carcinoma in asbestos workers who smoke cigarettes.