Aryl hydrocarbon hydroxylase in lymphocytes and lung tissue from lung cancer patients and controls

The relationship between aryl hydrocarbon hydroxylase activity and DNA adducts measured by (32)P-postlabelling assay in lymphocytes of lung cancer patients

We have investigated the correlation between DNA adduct levels and aryl hydrocarbon hydroxylase (AHH) activity in peripheral lymphocyte samples obtained from 42 lung cancer patients. DNA adducts and AHH activity were determined by the (32)P-postlabelling technique and the fluorometric method, respectively. The mean +/- SD of DNA adduct level was 0.88 +/- 0.37 (ranged from 0.22 to 1.90) per 10(8) nucleotides. The geometric means of non-induced and 3-methylcholanthrene (MC)-induced AHH activity, as well as AHH inducibility (MC-induced AHH activity/non-induced AHH activity) were 0.029, 0.228 pmol min(-1) 10(-6) cells, and 7.776, respectively. There was no statistically significant correlation between DNA adduct levels and non-induced or MC-induced AHH activity. A tendency of positive correlation was found between DNA adduct levels and AHH inducibility for the all subjects (n = 42, r = 0.25, p = 0.11). Such a positive correlation reached statistical significance in the subjects with squamous cell carcinoma (n = 13, r = 0.70, p < 0.01). In addition, similar correlation of DNA adducts with AHH inducibility was also observed in the GSTM1 present genotype (n = 17, r = 0.44, p = 0.07) and GSTP1-AA genotype (n = 29, r = 0.37, p = 0.05) individuals. These findings suggest that DNA adduct levels are mediated by CYP1A1 enzyme, and AHH inducibility may be a more relevant indicator than specific AHH activity for explaining the variation of DNA adduct levels in lymphocytes.

Tissue specific induction of cytochrome P450 (CYP) 1A1 and 1B1 in rat liver and lung following in vitro (tissue slice) and in vivo exposure to benzo(a)pyrene

Cytochrome P-450s (CYPs) detoxify a wide variety of xenobiotics and environmental contaminants, but can also bioactivate carcinogenic polycyclic aromatic hydrocarbons, such as benzo(a)pyrene (BaP), to DNA-reactive species. The primary CYPs involved in the metabolism and bioactivation of BaP are CYP1A1 and CYP1B1. Furthermore, BaP can induce expression of CYP1A1 and CYP1B1 via the aryl hydrocarbon receptor. Induction of CYP1A1 and CYP1B1 by BaP in target (lung) and non-target (liver) tissues was investigated utilizing precision-cut rat liver and lung slices exposed to BaP in vitro. Tissue slices were also prepared from rats pretreated in vivo with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to induce expression of CYP1A1 and CYP1B1. In addition, in vivo exposure studies were performed with BaP to characterize and validate the use of the in vitro tissue slice model. In vitro exposure of liver and lung slices to BaP resulted in a concentration-dependent increase in CYP1A1 and CYP1B1 mRNA and protein levels, which correlated directly with the exposure-related increase in BaP-DNA adduct levels observed previously in the tissue slices [Harrigan, J.A., Vezina, C.M., McGarrigle, B.P., Ersing, N., Box, H.C., Maccubbin, A.E., Olson, J.R., 2004. DNA adduct formation in precision-cut rat liver and lung slices exposed to benzo(a)pyrene. Toxicological Sciences 77, 307-314]. Pretreatment of animals in vivo with TCDD produced a marked induction of CYP1A1 and CYP1B1 expression in the tissue slices, which was similar to the levels of CYP1A1 and CYP1B1 mRNA achieved in liver and lung following in vivo treatment with BaP. Following in vitro exposure to BaP, the levels of CYP1A1 were greater in the lung than the liver, while following all exposures (in vitro and in vivo), the levels of CYP1B1 mRNA were greater in lung tissue compared to liver. The higher expression of CYP1A1 and CYP1B1 in the lung was associated with higher levels of BaP-DNA adducts in the lung slices (Harrigan et al.'s work) and together, these results may contribute to the tissue specificity of BaP-mediated carcinogenesis.

Differential response to benzo[A]pyrene in human lung adenocarcinoma cell lines: the absence of aryl hydrocarbon receptor activation

Benzo[a]pyrene (B[a]P) has been shown to produce DNA adducts and to initiate pulmonary carcinogenesis in animals. We observed differential susceptibility to B[a]P in two human lung adenocarcinoma cell lines, A427 and CL3. DNA adducts were induced by B[a]P treatment in CL3 cells, however, A427 cells were much less responsive to B[a]P treatment. Cytochrome P450 1A1 (CYP1A1) is involved in bioactivation of B[a]P in nonhepatic tissues. Cotreatment with alpha-naphthoflavone, a CYP1A1 inhibitor, abolished DNA adduct formation by B[a]P in CL3 cells. Nevertheless, CYP1A1 inducer beta-naphthoflavone, enhanced DNA adduct formation by B[a]P in both A427 and CL3 cells. Both enzyme activity and mRNA levels of CYP1A1 were highly induced by 1 or 10 microM B[a]P treatment for 24 hr in CL3 cells but not in A427 cells. Protein levels of AhR and aryl hydrocarbon receptor nuclear translocator (Arnt) were similar in A427 and CL3 cells before B[a]P treatment. However, B[a]P induced a retarded band with the [32P]-dioxin responsive element in CL3 cells, but not in A427 cells. This study demonstrated that variation in AhR-mediated CYP1A1 induction contributes to differential susceptibility to B[a]P-DNA adduct formation in human lung cells. Since AhR and/or Arnt function is impaired in A427 cells, this cell line offers a model for investigating the repression mechanisms of CYP1A1 induction by B[a]P in lung cells.

Cytochrome P450 1A1 in rat peripheral blood lymphocytes: inducibility in vivo and bioactivation of benzo[a]pyrene in the Salmonella typhimurium mutagenicity assay in vitro

The presence and inducibility of CYP1A1 in freshly isolated peripheral blood lymphocytes was examined in untreated rats and in rats pretreated with agents known to induce the enzyme in other tissues, as well as dexamethasone [CAS #50-02-2], which is not commonly associated with CYP1A1 induction. CYP1A1 but not CYP1A2 was detected by Western blot analysis of lymphocytes from untreated rats and was induced in lymphocytes from rats treated with the known CYP1A inducers beta-naphthoflavone [CAS #6051-87-2] or 3-methylcholanthrene [CAS #56-49-5] (7.3-fold), cigarette smoke (2. 8-fold), and pyridine [CAS #108-86-1] (2.6-fold). CYP1A1 was also induced in lymphocytes from rats treated with the nonprototypic inducer dexamethasone (17.7-fold) or bromobenzene [CAS #108-86-1] (3. 9-fold). Lymphocyte homogenate from rats treated with the inducers also catalyzed NADPH-dependent bioactivation of benzo[a]pyrene [CAS #50-32-8] to mutagens. The benzo(a)pyrene mutagenicity was detected using Salmonella typhimurium TA100 in the Ames test, and correlated positively with lymphocyte CYP1A1 content. The data show that CYP1A1 is present in rat peripheral blood lymphocytes in vivo, and is inducible by prototypic, as well as nonprototypic, inducers of the enzyme.

The molecular epidemiology of lung cancer

One in ten tobacco smokers develops bronchogenic carcinoma over a lifetime. The study of susceptibility of an individual and a population to lung cancer traditionally has been limited to the study of tobacco smoke dose and family history of cancer. New insights into lung carcinogenesis have made the study of molecular markers of risk possible in human populations in the emerging field of molecular epidemiology. This review summarizes data addressing the relationships of human lung cancer to polymorphisms of phase I procarcinogen-activating and phase II-deactivating enzymes and intermediate biomarkers of DNA mutation, such as DNA adducts, oncogene and tumor suppressor gene mutation, and polymorphisms. These parameters are reviewed as they relate to tobacco smoke exposure, procarcinogen metabolizing polymorphisms, and the presence of lung cancer. Problem areas in biomarker validation, such as cross-sectional data interpretation; tissue source, race, statistical power, and ethical implications are addressed.

Mitogen-activated lymphocytes: a good model for characterising lung CYP1A1 inducibility

The CYP1A1 hyperinducibility phenotype occurring in some 10% of the human population corresponds to a higher risk of developing lung cancer. This study was undertaken to assess whether the inducibility factor, generally evaluated on mitogen-activated lymphocytes after PAH induction, represents correctly the lung situation. Optimal experimental conditions were determined for evaluating, on both lymphocytes and lung tissue explants, the inducibility factor, defined as the ratio of EROD activity (CYP1A1-specific) to cytochrome c reductase activity (unaffected by PAH induction). Paired results for lymphocytes and lung tissue samples from 10 lung cancer patients were compared. A good correlation was observed between lymphocyte and lung tissue inducibilities (R = 0.809; p = 0.005). In conclusion, mitogen-activated lymphocyte inducibility is indicative of lung tissue inducibility and constitutes a good marker for evaluating individual PAH inducibilities.

Reducing effects of garlic constituents on DNA adduct formation in human lymphocytes in vitro

A water extract of raw garlic (RGE) and two organosulfur compounds, diallyl sulfide and S-allylcysteine (SAC), were evaluated for their relative effectiveness in reducing benzo[a]pyrene (BaP)-DNA adduct formation in stimulated human peripheral blood lymphocytes in vitro. In replicate experiments, RGE significantly inhibited BaP-DNA adduct formation at concentrations of 0.001, 0.01, and 0.1 mg/ml. SAC also significantly decreased BaP-DNA adduct formation at concentrations of 0.01 and 0.1 mg/ml. For diallyl sulfide, no significant reduction in BaP-DNA adduct formation was found. BaP-DNA adduct formation was not associated with cell viability or proliferation of peripheral blood lymphocytes after the various treatments. No clear scavenging activity was detected for the garlic constituents. Aryl hydrocarbon hydroxylase activity was not decreased, nor was formation of sulfate and glucuronide conjugates of 3-hydroxy-BaP increased in the presence of RGE and SAC, indicating that increased glutathione S-transferase activity or a more efficient repair of BaP-DNA adducts may explain the observed effects. In addition, reactive oxygen species-induced 8-oxodeoxyguanosine in DNA was reduced in the presence of SAC. It is concluded that raw garlic and SAC may be useful in the prevention of BaP-associated tumorigenesis and that further evaluation of their preventive potential in humans at risk appears feasible.

The relationship between aryl hydrocarbon hydroxylase and polymorphisms of the CYP1A1 gene

We examined the relationship between aryl hydrocarbon hydroxylase (AHH) and the frequency of a MspI mutation in the 3'-flanking region of cytochrome P450 (CYP) 1A1 (MspI polymorphism) and another mutation in exon 7 (Ile-Val polymorphism) in 84 healthy male subjects in Fukuoka, Japan. AHH inducibility (3-methylcholanthrene (MC)-induced AHH activity/non-induced AHH activity) was correlated with the MspI polymorphism (P < 0.0001) and age class (P = 0.015), whereas no correlation was found for the Ile-Val polymorphism (P = 0.509). Age-adjusted AHH inducibility (mean +/- SE) of the predominant homozygote (genotype A), the heterozygote (genotype B) and a homozygote rare allele (genotype C) genotypes was 4.89 +/- 0.36, 4.82 +/- 0.29 and 13.61 +/- 1.44, respectively. The genotype C showed much higher AHH inducibility than genotypes A and B (P < 0.001), while no significant difference was observed between genotypes A and B. Non-induced AHH activity was also correlated with these polymorphisms. The AHH activity of a homozygous mutant Val/Val genotype (0.076 +/- 0.010 pmol/min/10(6) cells) was significantly higher (P < 0.05) than that of the wild-type homozygous Ile/Ile (0.044 +/- 0.004 pmol/min/10(6) cells) and heterozygous Ile/Val (0.047 +/- 0.007 pmol/min/10(6) cells) genotypes. Our study suggests that the genotypes C and Val/Val, which are more frequent in smoking-related lung cancer, are closely related with high AHH inducibility and high non-induced AHH activity, respectively. Thus, the positive relationship between AHH inducibility and lung cancer is supported by our study. If our results are confirmed and the assessment of genotype becomes feasible on a population basis, identification of smokers who have genetically high susceptibility to lung cancer (genotype C or Val/Val) may become important for the prevention of lung cancer.

N-acetylcysteine (NAC) and glutathione (GSH): antioxidant and chemopreventive properties, with special reference to lung cancer

Lung cancer arises as a focal transformation of chronically injured epithelium with cigarette smoke as one of its well-recognized causes. Apart from oxidants (free radicals), cigarette smoke contains such a multitude of (pre)carcinogens that it is astonishing that not every heavy smoker becomes a victim of malignancy. This points to the interindividual variability in susceptibility to carcinogens; several lines of evidence suggest that metabolic factors are involved in such variability. Metabolism of carcinogens as well as the subsequent (multi)steps of carcinogenesis are affected by host factors and governed by the balance between opposing forces, such as metabolic activation and detoxification, formation and scavenging of radicals, and DNA damage and repair, which seem to imply that carcinogenic compounds can initiate tumor growth only in amounts saturating detoxification mechanisms. In this context it is well known that glutathione (GSH) plays a crucial role in the detoxification of xenobiotics. N-Acetylcysteine (NAC), an aminothiol and synthetic precursor of intracellular cysteine and GSH, has been used for many years in Europe as a mucolytic drug. Clinically, it is a safe agent without major side effects and has been considered to have a place in cancer prevention, too. The antimutagenic and anticarcinogenic properties of NAC could be ascribed to multiple protective mechanisms, such as NAC nucleophilicity, antioxidant activity, its ability to act as a precursor of intracellular reduced GSH, modulation of detoxification, and DNA repair processes. On these grounds, NAC has emerged as a most promising cancer chemopreventive agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Aryl hydrocarbon hydroxylase activity in chemically induced and toremifene-treated mammary tumors in rats

Aryl hydrocarbon hydroxylase (AHH) and NADPH-cytochrome P450 reductase (NCR) activity of microsomes from liver, lungs, uterus and mammary tumors in dimethylbenzanthracene-induced and toremifene-treated female Sprague-Dawley rats were studied. AHH and NCR activity in tumors and uteri was low compared with that in livers and lungs. The distribution of AHH in tumors was wide and skewed. It varied in different tumors of the same animal as widely as between different animals. The enzyme activity in tumors did not correlate with that in the liver, lungs or uterus of the same animal. Toremifene had no effect on AHH or NCR in tumor or liver, but it decreased them in lungs. Tumor AHH activity correlated with its overall growth rate and development stage. The results suggest that malignant transformation leading to the defect in growth regulation also confuses the complex regulatory system of AHH activity.

Cytochrome P450IA1 activity in human myometrium and uterine leiomyoma: influence of smoking

A xenobiotic-metabolizing enzyme, the P450IA1 (aryl hydrocarbon hydroxylase; AHH) was measured fluorometrically in myometrium and in uterine leiomyoma tissues. The material included both myometrium and leiomyoma tissue samples from 62 leiomyoma patients and 22 tissue samples of normal myometrium obtained from leiomyoma-free patients undergoing hysterectomy. Among 62 leiomyoma patients there were 14 cigarette-smokers and 48 non-smokers, and among 22 control patients 6 and 16, respectively. The P450IA1 activity of the leiomyomas was significantly (P < 0.0005) higher than that of the surrounding myometrium in both smoker and non-smoker groups. In smokers, myometrium an obvious induction of P450IA1 was seen. Smoking increased the P450IA1 activity also in the leiomyoma, but the increase was not statistically significant. Our study supports the idea that myometrial tissue can respond to xenobiotics from the environment.

The Role of Pharmacogenetics in Cancer Chemotherapy and the Development of Malignancy

The role of pharmacogenetics in the area of cancer chemotherapy and the development of malignancy has not been well defined. Only four chemotherapeutic agents have been evaluated for toxicity or clinical response based on genetic differences in metabolism. These include 5-fluorouracil, 6-mercaptopurine, amonafide, and cyclophosphamide. Severe toxicity of 5-fluorouracil and amonafide due to individual differences in drug metabolism has been reported in the literature. Tumor response in leukemic children may be associated with genetic differences in metabolism of 6-mercaptorpurine. The development of malignancy may be secondary to an individual's ability to detoxify carcinogens found in the environment. For example, the incidence of bladder cancer appears higher in subjects who have occupational exposure to aromatic amines and the slow acetylator phenotype. Some evidence also exists that smokers who are very extensive metabolizers of debrisoquin may be more prone to developing lung cancer. Strong evidence for an association between other cancer types and pharmacogenetics requires more study.

Carcinogen metabolism and DNA adducts in human lung tissues as affected by tobacco smoking or metabolic phenotype: a case-control study on lung cancer patients

Individual variations in activity of pulmonary enzymes that metabolize tobacco-derived carcinogens may affect an individual's cancer risk from cigarette smoking. To investigate whether some of these enzymes (e.g., cytochrome P450IA-related) can serve as markers for carcinogen-induced DNA damage accumulating in the lungs of smokers, non-tumorous lung tissue specimens were taken during surgery from middle-aged men with either lung cancer (n = 54) or non-neoplastic lung disease (n = 20). Phase I (AHH, ECDE) and phase II (EH, UDPGT, GST) enzyme activities, glutathione and malondialdehyde contents were determined in lung parenchyma and/or bronchial tissues; some samples were analyzed for DNA adducts, using 32P-postlabeling. Data analysis of subsets or the whole group of patients yielded the following results. (1) Phase I and II drug-metabolizing enzyme (AHH, EH, UDPGT, GST) activities in histologically normal surgical specimens of lung parenchyma were correlated with the respective enzyme activities in bronchial tissues of the same subject. (2) In lung parenchyma, enzyme (AHH, ECDE, EH, UDPGT) activities were significantly and positively related to each other, implying a similar regulatory control of their expression. (3) Mean activities of pulmonary enzymes (AHH, ECDE) were significantly (2- and 7-fold, respectively) higher in lung cancer patients who had smoked within 30 days before surgery (except GST, which was depressed) than in cancer-free subjects with a similar smoking history. (4) In the cancer patients, the time required for AHH, EH and UDPGT activities to return to the level found in non-smoking subjects was several weeks. (5) Bronchial tree and peripheral lung parenchyma preparations exhibited a poor efficiency in activating promutagens to bacterial mutagens in Salmonella. However, they decreased the mutagenicity of several direct-acting mutagens, an effect which was more pronounced in tissue from recent smokers. GSH concentration and GST activity were positively correlated with mutagen inactivation in the same sample. (6) In recent smokers, AHH activity in lung parenchyma was positively correlated with the level of tobacco smoke-derived DNA adducts. (7) Pulmonary AHH and EH activity had prognostic value in tobacco-related lung cancer patients. (8) An enhanced level of pro-oxidant state in the lungs was associated with recent cigarette smoking. Malondialdehyde level in lung parenchyma was associated with the degree of small airway obstruction, suggesting a common free radical-mediated pathway for both lung cancer induction and small airway obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity: partial protection against striato-nigral dopamine depletion in C57BL/6J mice by cigarette smoke exposure and by beta-naphthoflavone-pretreatment

This study aimed to find a possible biochemical basis for the frequent epidemiological observation of a negative correlation between smoking and Parkinson's disease. The effects of cigarette smoke exposure and of beta-naphthoflavone (BNF)-pretreatment on corpus striatal dopamine depletion by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were studied using the mouse MPTP model. Brain and hepatic monoamine oxidase (MAO) activity, hepatic cytochrome P450 content, BNF-inducible ethoxyresorufin O-dealkylase (EROD) activity and corpus striatal dopamine levels were measured. Cigarette smoke exposure partially protected against corpus striatial dopamine depletion by MPTP. This protection was associated with monomaine oxidase (MAO) inhibition in brain and liver, as well as with cytochrome P450 induction. BNF pretreatment also partially protected against MPTP-induced depletion of striatal dopamine. This was associated with a strong induction of cytochrome P450 but not inhibition of MAO activity. Our findings suggest that both MAO inhibition and cytochrome P450 induction may play a role in any biochemical protection afforded by cigarette smoke exposure against the development of Parkinson's disease.

Is aryl hydrocarbon hydroxylase activity a new prognostic indicator for breast cancer?

Aryl hydrocarbon hydroxylase (AHH) activity was measured in the breast tumours of 153 primary and 17 recurrent cancer patients, and in 18 patients with benign breast tumour. All operations were carried out in 1983-84. The cytosolic fraction was collected for steroid receptor determination, and microsomes were separated for AHH assay from the same tissue samples. The AHH distribution was wide and highly skewed in all groups. About 10% of the samples showed activities below detection limit. The medians and ranges for primary cancers were 34 (less than 5-2683), for recurrent cancers 40 (20-239) and for benign tumours 11 (less than 5-37) fmol min-1 mg-1 protein. After logarithmic transformation, the mean AHH activities of cancer samples differed significantly from those of benign tumours. The logarithm of AHH activity (log AHH) correlates positively with axillary lymph node status, and negatively with steroid receptor levels. The development of the disease and the survival of the patients were followed for 4 years. The survival and the disease-free interval of the cancer patients who had low AHH activity was significantly higher than that of the high AHH group. The multivariate analysis with Cox's proportional hazad model showed primary tumour size, progesterone receptor concentration, nodal status and log AHH to be the most important independent prognostic factors for survival, while the occurrence of metastases, log AHH and tumour size were the equivalent factors for the disease-free interval in primary breast cancers. We conclude that AHH activity may reflect the overall malignant potential of breast cancer tissue.

Effects of recombinant human interferon alpha on aryl hydrocarbon hydroxylase activity in cultured human peripheral lymphocytes

Interferon and its inducers are known to depress drug biotransformation in vivo by decreasing the levels of cytochrome P-450 (P450) monooxygenase system in the liver. However, very little is known about the effects of interferon on P450 in extrahepatic tissues. In this study we investigated the effects of a recombinant human interferon-alpha (rhIFN-alpha) on aryl hydrocarbon hydroxylase (P450IAI) in cultured human peripheral lymphocytes (HPL). Non-induced and induced (3-methylcholanthrene) mitogen activated lymphocytes were used throughout the study. rhIFN-alpha maximally depressed AHH activity to approximately 58% of control after 24 hrs of incubation in both non-induced and induced lymphocytes. However, after 48 hrs of incubation with rhIFN-alpha, AHH activity had recovered to 86% of control in induced cells and 61% in non-induced cells. rhIFN-alpha had no significant effect on either NADH cytochrome c reductase activity or on viable lymphocyte cell count. This is the first demonstration that rhIFN-alpha can have a direct depressive effect on a P450 dependent monooxygenase system in HPL.

Influence of cigarette smoking on the levels of DNA adducts in human bronchial epithelium and white blood cells

The presence of carcinogen-DNA adducts in human tissues is evidence of exposure to carcinogens and may be an indicator of cancer risk. DNA was isolated from non-tumorous bronchial tissue of 37 cigarette smokers, 8 former smokers and 8 non-smokers and analyzed for the presence of aromatic and/or hydrophobic DNA adducts in the 32P-post-labelling assay. Adducts were detected as bands of radioactive material when 5'-32P-labelled deoxyribonucleoside 3',5'-bisphosphates were chromatographed on polyethyleneimine-cellulose tlc plates, and the patterns indicated the formation of adducts by a large number of compounds. Adduct levels detected in DNA from non-smokers, former smokers and current smokers were 3.45 +/- 1.62, 3.93 +/- 1.92 and 5.53 +/- 2.13 adducts/10(8) nucleotides, respectively. The differences in adduct levels between smokers and former and non-smokers were statistically significant (p less than 0.01); and among the smokers, significant correlations were found between adduct levels and both daily cigarette consumption and total cigarette consumption (daily consumption X number of years smoked). DNA was also isolated from the peripheral-blood leukocytes of 31 heavy smokers (greater than 20 cigarettes/day) and 20 non-smokers and analyzed by 32P-post-labelling. Adduct levels in the smokers' samples were not significantly different from levels in the non-smokers' samples (2.53 +/- 1.31 and 2.12 +/- 1.44 adducts/10(8) nucleotides, respectively). Thus, evidence for carcinogen exposure was found in human bronchial epithelium, a target tissue for tobacco-induced tumour formation, but not in peripheral-blood cells, indicating possible limitations in the use of the latter as a surrogate, non-target tissue source of DNA for monitoring human exposure to inhaled carcinogens.

Possible prognostic value of pulmonary AH-locus-linked enzymes in patients with tobacco-related lung cancer

As prognosis in breast cancer patients has been related to the AHH activity in their breast tissue, we have conducted a similar analysis on pulmonary drug metabolizing enzymes as prognostic markers for male lung cancer patients, primarily investigated for other reasons. A subset of 50 patients with lung cancer related to tobacco use, who had undergone thoracic surgery, was re-analyzed. The activity of parenchymal aryl hydrocarbon hydroxylase (AHH) and epoxide hydrolase (EH) that had been determined previously in homogenates of non-neoplastic surgical lung specimens, was used for comparisons of the patients' survival after surgery. When the crude mortality percentages at 1 and 2 years by AHH or EH activity, subdivided into quarters of the distribution, were calculated, a lower mortality was related to lower enzyme levels. Subjects in the 1st and 4th quarters of the distribution showed significant differences in their 1-year survival for AHH (p = 0.05) and EH (p less than 0.01) activities. This relationship could not be accounted for by age, cumulative lifetime smoking, recent or continuing smoking, stage or histological type of disease. Thus, the levels of pulmonary AHH and EH may have some prognostic significance in tobacco-related lung cancer.

Spectroscopic quantitation of cytochrome P-450 in human lung microsomes

The cytochrome P-450 content of human lung microsomes was measured by difference spectroscopy of the carbon monoxide-complexed hemoprotein. These measurements were only possible after the microsome preparation had been subjected to centrifugation over a discontinuous sucrose gradient, to remove an opaque black contaminant. The specific concentration of total cytochrome P-450 in human lung microsomes is essentially identical to that of microsomes prepared under identical conditions from untreated baboon lungs, but is only 0.7% of the specific content found in lung microsomes from untreated rabbits. These measurements correspond well to the observed metabolic capacities of the various microsome samples.

Effects of acute physical exercise on aryl hydrocarbon hydroxylase activity in human peripheral lymphocytes

It has been reported that physical exercise may enhance cytochrome P-450 dependent drug metabolism in vivo. In this study we report that the specific activity of aryl hydrocarbon hydroxylase (AHH) in human peripheral lymphocytes (HPL) is enhanced approximately two fold following acute physical exercise. This enhancement of AHH activity in HPL appears to be strongly correlated with enhanced lymphocyte count as well as induced metabolic and exercise stress but not with the intrinsic physical fitness of individuals.

Benzo[a]pyrene-induced immunotoxicity: comparison to DNA adduct formation in vivo, in cultured splenocytes, and in microsomal systems

Benzo[a]pyrene (BaP)/DNA adduct formation appears to be involved in carcinogenesis, but the relationship between adduct formation and BaP-induced immunotoxicity is unknown. We compared DNA adduct formation (32P-postlabeling analysis) to suppression of polyclonal immune responses (3H-TdR incorporation and IgM secretion) and decreases in cell viability in B6C3F1 female mouse splenic leukocytes (SPL). BaP administration (200 mg/kg, ip) resulted in suppression of polyclonal responses and substantial DNA adduct formation in mouse SPL. SPL adduct levels were similar to those in liver, lung, kidney, and stomach. In vitro exposure of SPL to BaP without rat liver activation enzymes (S9) caused decreases in SPL viability and immune responses that were dependent on dose and exposure period. However, DNA adduct formation in SPL was very low between 1 and 200 microM BaP. S9 enhanced the toxicity of BaP for SPL cultures. Adduct formation was rapid and dose related in +S9 incubates. The low level of BaP activation by SPL was confirmed in microsomal incubations in which splenic microsomes exhibited much lower aryl hydrocarbon hydroxylase (AAH) activity and ability to form DNA-adducting metabolites than did microsomes from liver or lung. Results indicate that immunosuppression produced by BaP in these systems was due to cytotoxic effects. It appears that these effects were caused by two separate mechanisms, one dependent on and one independent of DNA adduct formation. Since SPL had high levels of DNA adducts after ip injection of BaP, reactive metabolites of BaP may be involved in the immunotoxicity seen in vivo.