Pulmonary metabolism of mutagens and its relationship with lung cancer and smoking habits.

The S-12 fractions of lung peripheral parenchyma obtained from 80 male individuals, aged 17-71 years, were assayed as blind samples for the ability either to convert promutagens into bacterial mutagens or to decrease the potency of direct-acting mutagens in the Ames reversion test. In this system, lung preparations were completely ineffective in activating an N-nitroso compound (i.e., N-nitrosomorpholine) and polycyclic aromatic hydrocarbons [i.e., 3-methylcholanthrene and benzo(a)pyrene] or their metabolites [i.e., 3-hydroxy-benzo(a)pyrene and benzo(a)pyrene-trans-7,8-diol]. They yielded a borderline and sporadic activation of a cigarette smoke condensate, and a weak but frequent activation of an aromatic amine (i.e., 2-aminofluorene), of a heterocyclic amine (i.e., 2-amino-3,4-dimethylimidazo[4,5-f] and of a diamide (i.e., cyclophosphamide). The pulmonary metabolism was more oriented in the sense of detoxification, as shown by the consistent decrease of potency of direct-acting mutagens, including a metal (i.e., sodium dichromate), an acridine and nitrogen mustard derivative (i.e., 2-methoxy-6-chloro-9-[3-(2-chloromethyl)aminopropylamino]acridine or ICR 191), an epoxide (i.e., epichlorohydrin) and an N-oxide (i.e., 4-nitroquinoline-N-oxide). As assessed by means of a numerical score quantifying the variation of mutagenicity, a marked interindividual variability (up to 20-fold) was detected in the ability of lung specimens to affect the mutagenicity of test compounds. Such variability was not significantly related to the protein concentration of S-12 fractions, nor to the age of the patients under scrutiny, who during hospitalization were on normal institutional diets and did not receive any special drug treatment. The only significant difference between 20 noncancer and 60 lung cancer patients, irrespective of the histological type, was a decreased activation of cyclophosphamide in the latter group. Probably due to the high prevalence of smokers among lung cancer patients, a significantly decreased activation of cyclophosphamide was also observed in the group of smokers. Smoking habits were associated with a stimulation of detoxifying mechanisms which, in agreement with the results of a previous study with human alveolar macrophages (F. L. Petrilli et al., J. Clin. Invest., 77:1917-1924, 1986), was significant in the case of sodium dichromate. Such effect was further enhanced by considering only individuals smoking during the last 24 h before collecting lung specimens, and under these conditions it became significant also for ICR 191.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-lasting effects of tobacco smoking on pulmonary drug-metabolizing enzymes: a case-control study on lung cancer patients.

Lung tissue specimens were taken during surgery from middle-aged men with either lung cancer (LC, n = 54) or a nonneoplastic lung disease (n = 20). Aryl hydrocarbon hydroxylase (AHH), 7-ethoxycoumarin O-deethylase (ECDE), epoxide hydrolase (EH), glutathione S-transferase (GST), and UDP-glucuronosyltransferase (UDPGT) activities and glutathione and malondialdehyde contents were determined in 12,000 X g supernatant fractions from nontumorous parenchymal tissues. Interindividual differences in enzyme activities ranged from 11- to 440-fold, and glutathione content varied by 17-fold; the values showed unimodal distributions. AHH, ECDE, EH, and UDPGT activities were significantly and positively correlated to each other; a significant negative correlation was found between GST and the other enzymes. A relationship between enzyme activity and number of cigarettes smoked (pack-years) was found only for GST. Ignoring detailed smoking histories in the 6-month period preceding surgery, no difference was found in enzyme activities or glutathione content between LC and nonneoplastic lung disease patients or between smokers and nonsmokers. However, when the number of days since stopping smoking was considered, in smokers a significant increase was found for AHH, EH, and UDPGT activities and a significant decrease was found for GST activity, as compared to nonsmokers. LC patients who had smoked until the day before surgery had higher activities of AHH, ECDE, EH, and UDPGT than nonsmokers, while GST activity was reduced by one-third. The activities of these enzymes returned to the basal level found in nonsmokers within 59 (AHH), 108 (EH), 67 (UDPGT), and 40 (GST) days. LC patients who were recent smokers (within 30 days prior to surgery) had significantly induced AHH and ECDE activities when compared with smoking nonneoplastic lung disease patients. These results show that pulmonary drug metabolism can be altered by tobacco smoking and that these effects can last 40 to 108 days after cessation of smoking. These new findings should be considered in studies on the role of carcinogen-metabolizing enzymes in determining susceptibility to lung cancer.