Xenobiotic-metabolizing enzyme activity in human non-small-cell derived lung cancer cell lines

Transcription initiation activity of adenovirus left-end sequence in adenovirus vectors with e1 deleted

We analyzed the transcription initiation activity of the left-end sequence (first 342 bp) of the adenovirus genome in the context of an adenovirus vector with E1 deleted in in vitro and in vivo gene transfer models. While nucleotide sequences 1 to 190 and 1 to 342 showed strong activity in three out of three lung cancer cell lines, nucleotide sequence 1 to 103 showed limited activity in H358, cells which show characteristics of type 2 alveolar cells. In vivo, the transcription initiation activities of nucleotide sequence 1 to 103 in the liver and the lung were minimal, while nucleotide sequences 1 to 190 and 1 to 342 showed strong activity comparable to that of the cytomegalovirus promoter. Further understanding of the transcription initiation activity of the left-end sequence of the adenovirus genome should lead to optimization of adenovirus vectors.

Role of the lung in accumulation and metabolism of xenobiotic compounds--implications for chemically induced toxicity

The mammalian lung is exposed to and affected by many airborne and bloodborne foreign compounds. This review summarizes the role of lung in accumulation and metabolism of xenobiotics, some of which are spontaneously reactive or are metabolically activated to toxic intermediates. The specific architectural arrangement of mammalian lung favors that so-called pneumophilic drugs are filtered out of the blood and are retained within the tissue as shown in particular for amphetamine, chlorphentermine, amiodarone, imipramine, chlorpromazine, propranolol, local anaesthetics, and some miscellaneous therapeutics. There is strong evidence that intrapulmonary distribution activity and regulation of drug-metabolizing enzymes in lung is distinct from liver. This review focuses on the metabolic rate of selected compounds in lung such as 5-fluoro-2'-deoxyuridine, local anesthetics, nicotine, benzo(alpha)pyrene, ipomeanol, 4-methylnitrosamino-1-(3-pyridyl)-1-butanone. It is widely accepted that the formation of radical species is a key event in the pneumotoxic mechanisms induced by bleomycin, paraquat, 3-methylindole, butylhydroxytoluene, or nitrofurantoin. Finally, methodological approaches to assess the capacity of lung to eliminate foreign compounds as well as biochemical features of the pulmonary tissue are evaluated briefly.

Secretion of mucus proteinase inhibitor and elafin by Clara cell and type II pneumocyte cell lines

The regulation of proteinases secreted by neutrophils is very important for the prevention of tissue injury. We recently described the isolation of elafin from bronchial secretions, a new elastase-specific inhibitor that is also found in the skin of patients with psoriasis. In this study, we investigated the secretion of elafin and mucus proteinase inhibitor (MPI), another inhibitor showing sequence similarity with elafin, in two lung carcinoma cell lines, NCI-H322 and A549, which have features of Clara cells and type II alveolar cells, respectively. The results presented show that the two inhibitors are produced when the cells are cultured either in serum-free or in serum-containing media. MPI was detected immunologically as a unique molecule of M(r) 14 kD, in accordance with previous studies. Conversely, one or two elafin-immunoreactive species were detected depending on the cell line: a 12- to 14-kD species was observed in the A549 cell line, regardless of the culture conditions, whereas in the NCI-H322 cell line we detected a 6-kD species in serum-containing (10% fetal calf serum) conditions and a 12- to 14-kD species in serum-free conditions. The 12- to 14-kD molecule probably represents an active precursor of elafin. Whether the cleavage of the 12- to 14-kD precursor giving rise to the elafin molecule is of any physiologic significance is not known. In showing for the first time that MPI and elafin (and its precursor) are secreted by the A549 cell line, this report implicates the type II alveolar cell in the defense of the peripheral lung against the neutrophil elastase secreted during inflammation.

Cytochrome P-450 induction in human lung tumor-derived cell lines. Characterisation and effects of inflammatory mediators

Cytochrome P-450 species (P-450) comprise a polymorphic multigene family of heme-containing enzymes which are essential to the phase-I metabolism of xenobiotics. Induction of P-450 species by drugs and carcinogens has been extensively studied; endogenous regulation of P-450 also occurs during normal development and disease. The aim of this project was to study the in-vitro induction of P-450 and its modulation by inflammatory mediators in the human lung tumor-derived cell lines NCI H322 and NCI H358. The cell lines expressed detectable levels of 7-ethoxyresorufin O-deethylase which could be induced by benzanthracene. After benzanthracene treatment, a protein tentatively identified as isozyme CYP1A1 was detected by Western-blot analysis and a concommitant increase in CYP1A mRNA expression was observed. Optimal induction was observed at a benzanthracene concentration of 5 micrograms/ml with cells grown in RPMI medium containing 10% fetal calf serum. The effects of endotoxin, dexamethasone and five recombinant DNA-derived cytokines, interleukin-1 beta, tumor necrosis factor, and interferons alpha, beta and gamma, on constitutive and benzanthracene-induced ethoxyresorufin O-deethylase activity were examined in NCI H322 cells. Of all the lymphokines studied, only interferon gamma had any marked effect. Administration of this lymphokine strongly suppressed ethoxyresorufin O-deethylase activity in both control and benzanthracene-treated cells.

Metabolic activation and biological effects of nitrosamines in the mammalian lung

Nitrosamines and their precursors are among the most common contaminants of our environment, and many of them are highly carcinogenic. Nitrosamines are believed to require metabolic activation in the host organism, and many of them demonstrate a pronounced organ and cell type specificity. This review summarizes recent in vivo and in vitro experiments which focus on the mechanisms of nitrosamine-induced lung carcinogenesis. Currently available in vivo and in vitro data suggest that nitrosamines may be metabolized by cytochrome P-450, prostaglandin endoperoxide synthetase, or monoamine oxidases. The presence of one or the other of these enzyme systems may be partially responsible for the cell type-specific effects of this class of chemicals. Moreover, evidence in vitro suggests selective uptake of nitrosamines by cell type-specific receptors, a phenomenon which offers a more logical explanation than previously published theories for the selectivity of biological effects exerted by nitrosamines.

Metabolism and cytotoxicity of benzo(a)pyrene in the human lung tumour cell line NCI-H322

1. The human lung tumour cells NCI-H322 metabolized benzo(a)pyrene (BP) at a rate of 160 pmol/10(6) cells/h for at least 8 h. About 30% of the total metabolites were water-soluble, 30% of which were conjugates with glutathione. The water-soluble fraction also contained BP sulphates but no BP glucuronides. 2. The cytotoxic potency of BP and its metabolites, 3-hydroxybenzo(a)pyrene (3-OH-BP) and (+/-) anti-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene (7,8-diol-BP), differed by an order of magnitude with the ranking 7,8-diol-BP greater than BP greater than 3-OH-BP. The cytotoxicity of BP was not detected at the end of a 24 h treatment period but became increasingly apparent at later times. In contrast, the cytotoxicity of 3-OH-BP was observed immediately after the treatment period and did not increase greatly thereafter. 7,8-Diol-BP caused both 'immediate' and 'late' effects. 3. The time course and concentration dependence suggested that the cytotoxicity of BP in NCI-H322 cells was not attributable to the formation of 3-OH-BP, but more likely resulted from the formation of other products such as 7,8-diol-BP.

Inhibition of N-diethylnitrosamine metabolism by human lung cancer cell lines with features of well differentiated pulmonary endocrine cells

Cell lines derived from a human pulmonary carcinoid tumor (NCI-H727) and from a human pulmonary large cell carcinoma (NCI-H460) were investigated by transmission electron microscopy. Both cell lines, at early in vitro passage, demonstrated ultrastructural features of well differentiated pulmonary endocrine cells. Line NCI-H727 had more endoplasmic reticulum than line NCI-H460 and demonstrated L-dopa decarboxylase activity as well as production of calcitonin and bombesin. Because of their ultrastructural resemblance with normal pulmonary endocrine cells, these cell lines were used to test the theory derived from experiments in hamsters that human pulmonary endocrine cells can metabolize N-nitrosodiethylamine (DEN). The cells were incubated in vitro with [14C]DEN. Metabolism was assessed by 14CO2 production. Both cell lines metabolized DEN to a much greater extent than previously investigated human lung cancer cell lines of Clara cell and alveolar type II cell morphology. In keeping with its abundant endoplasmic reticulum, line NCI-H727 yielded 14CO2 in the 300 nM range, whereas NCI-H460 was less active. Metabolism was time dependent. Preincubation with various enzyme inhibitors yielded a highly significant inhibition of DEN metabolism with the two inhibitors of the fatty acid cyclooxygenase component of prostaglandin endoperoxide synthetase, aspirin and indomethacin. Inhibitors of cytochrome P-450 (CO, piperoxylbutoxide) did not inhibit DEN metabolism. Preincubation with sinigrin yielded similar negative results as CO and piperonylbutoxide. Our data are in support of the theory that human pulmonary endocrine cells can metabolize nitrosamines. Moreover, the experiments with enzyme inhibitors suggest that in this cell type such metabolism is largely dependent on prostaglandin endoperoxide synthetase.

Expression of glutathione S-transferase and phenol sulfotransferase, but not of UDP-glucuronosyltransferase, in the human lung tumor cell lines NCI-H322 and NCI-H358

The expression of xenobiotic-metabolizing enzymes was studied in the human lung tumour cell lines NCI-H322 and NCI-H358. These cells are derived from adenocarcinomas and exhibit features of Clara cells and alveolar type II cells, respectively. Examination of the in vitro activities showed that both cell lines lack UDP-glucuronosyltransferase against the substrates 3-hydroxybenzo[a]pyrene (3-OH-BaP) and 4-hydroxybiphenyl (4-OH-Bph) and that in vitro conjugation of sulfate with 3-OH-BaP was only just detectable. In contrast, both cell lines showed fairly high levels of glutathione-S transferase activity with the substrate 1-chloro-2,4-dinitro-benzene (54.4 and 83.0 nmol/min X mg protein, respectively) and of glutathione (81 and 41 nmole/mg protein, respectively). The metabolic capacity of intact NCI-H322 and NCI-H358 cells was examined using benzo[a]pyrene (BaP) and 3-OH-BaP as substrates. The cell lines formed sulfate conjugates from 3-OH-BaP (4.5 and 0.4 pmol/min X mg protein, respectively) but did not produce any detectable glucuronides. When cultures of the two cell lines were exposed to BaP, phenolic products accumulated in the growth medium. NCI-H322 cells also formed some sulfate conjugates, whereas such conjugates were barely detectable in the medium of NCI-H358 cells. In contrast A549, a human pulmonary adenocarcinoma cell line known to contain UDP-glucuronosyltransferase activity, efficiently conjugated 3-OH-BaP to glucuronic acid and converted the primary phenolic products formed from BaP to glucuronides. Thus the NCI-H322 and NCI-H358 cells are exceptional in that they possess no or very little glucuronosyltransferase activity but exhibit appreciable monooxygenase activity. The cell lines may therefore be of interest for examining the biological effects of potentially toxic chemicals which are otherwise detoxified by glucuronic acid conjugation. The cells may also be useful as test systems for evaluating the potential cytotoxicity and genotoxicity of chemicals to human lung.