[Show abstract][Hide abstract]ABSTRACT: The presence and inducibility of specific CYPs (1A1, 1A2, 1B1, 2B22, 3A22, 3A29 and 3A46) and the related transcriptional factors (AhR, CAR, PXR, and HNF4alpha) were investigated, at activity and/or transcriptional level, in liver, respiratory and olfactory mucosa of control and beta-naphthoflavone (betaNF)-treated pigs an agonist of AhR, or rifampicin (RIF), an agonist of PXR. Experiments with real-time PCR showed that CYP1A1 mRNA was enhanced by betaNF, although at different extent, in liver, respiratory and olfactory tissues, whereas mRNAs of CYP1A2 and 1B1 were increased only in liver. Accordingly, in microsomes of both nasal tissues, the transcriptional activation of CYP1A1 was accompanied by an induction of ethoxyresorufin deethylase activity (a marker of this isoform) but not of methoxyresorufin demethylase activity (a marker of CYP1A2). The rifampicin treatment resulted in a transcriptional activation of CYP2B22 and CYP3As genes in liver but not in respiratory and olfactory mucosa. In parallel, the marker activity of CYP2B (ethoxy 4-(trifluoromethyl)coumarin deethylase) and CYP3As (6beta-testosterone hydroxylase and benzyloxyquinoline debenzylase) were induced in liver microsomes but not in the nasal ones. Considering the transcriptional factors, the basal expression of AhR mRNA was found to be as high in liver as in both nasal tissues but not susceptible to induction by betaNF. Also PXR mRNA was found, aside liver, well expressed in the nasal tissues, whereas CAR and HNF4alpha mRNAs were barely detected. In any case, these transcripts appeared to be enhanced by RIF treatment. Our results demonstrated that in the respiratory and olfactory mucosa of pig, although the presence of AhR, only CYP1A1, but not 1A2 and 1B1 resulted to be inducible by betaNF. Similarly, it was observed that in these nasal tissues, although the presence of PXR, neither CYP2B22 nor any CYP3A resulted to be inducible by RIF. Thus, the regulation mechanism of CYP1A2, 1B1, 2B22, 3A22, 3A29, and 3A46, in the nasal mucosa involves tissue-enriched transcriptional factors others than AhR, CAR, PXR, and HNF4alpha, which are fundamental in liver.
[Show abstract][Hide abstract]ABSTRACT: Humans are exposed daily to electromagnetic fields (EMFs) originating from a variety of devices and systems. During the 1980s many reports of potential mutagenic, teratogenic, and carcinogenic effects of EMFs were published, sometimes with contrasting results. To date, no study has established unequivocally a causal relationship between EMFs and cancer. Cell cultures can provide a simple and inexpensive tool for the study of the effects of EMFs. We have used the Chinese hamster V79 cell line to evaluate the influence of a sinusoidal EMF at 50-Hz with a constant flow of 2 G on the induction of HGPRT- mutants and on survival. Our results showed that the EMF employed did not induce any modification of mutation frequency, but the results on survival were contrasting. When only 10(2) cells were plated, a reduction in the number of colonies, reaching about 50% after 10 days of treatment, was observed; however, when 2 x 10(5) cells or more were seeded, no reduction in viability was recorded. An intercellular metabolic interaction may explain these results.
No preview · Article · Jan 2009 · Journal of Environmental Pathology Toxicology and Oncology
[Show abstract][Hide abstract]ABSTRACT: The presence and inducibility of CYP enzymes belonging to the family 1 (CYP 1A1, 1A2 and 1B1) and AhR have been studied in liver, lung, kidney and heart of control and beta-naphthoflavone (beta NF)-treated pigs. Segments of so far undescribed genes for porcine CYP 1A2, 1B1 and AhR were identified by RT-PCR and their sequences found to be highly homologous to those of the corresponding human genes. The mRNA level of CYP 1A1 was induced by beta NF, although to a different extent, in liver, lung, kidney and heart. This transcriptional activation of CYP 1A1 was accompanied in microsomes of all these organs by an induction of 7-ethoxyresorufin deethylase activity (a marker of this isoform) and an increase in a protein band immunoreactive with anti-rat CYP 1A1. An increase in CYP 1A2 transcription and in activity of microsomal 7-methoxyresorufin demethylase and acetanilide 4-hydroxylase (both markers of 1A2) was observed in the liver and, to a very small extent, in the lung but not in kidney and heart. As to CYP 1B1, its transcription was detected in liver, lung and heart only following the beta NF treatment; however this mRNA expression did result in any detectable microsomal 17beta-estradiol 4-hydroxylase activity (a marker of this isoform). The CYPs induced by beta NF were further investigated by using some other marker activities. It was found that porcine CYP 1A1 and 1A2, unlike the human counterparts, could only deethylate 7-ethoxycomarin to a very small extent, if at all, whereas 7-ethoxy 4-trifluoromethylcoumarin was a good substrate for pig CYP 1A1. Overall, our results demonstrated a differential expression and regulation of the AhR-mediated CYP genes in liver, lung, kidney and heart of the pig.naphthoflavone.
[Show abstract][Hide abstract]ABSTRACT: Several CYP enzymes are expressed in the lung of mammals but studies on their regulation have been rather neglected. In this study, the CAR and PXR expression and the inducibility of CYP 2B and CYP 3A isoforms in the lung rats and rabbits were investigated. Rats were treated with phenobarbital, clotrimazole or a mixture of dexametasone plus pregnenolone 16alpha-carbonitrile, whereas rabbits were treated with phenobarbital or rifampicin. A low constitutive expression of CAR mRNA was demonstrated by RT-PCR analysis in the lung of rat but not in rabbit. Phenobarbital treatment did not change the CAR expression profiles and did not induce in either rats and rabbits the pulmonary CYP 2B isoforms, as judged by western blot analysis and the marker pentoxyresorufin O-dealkylase and 7-ethoxy-4-trifluoroethylcoumarin O-deethylase activities. On the contrary, these marker activities were strongly induced by phenobarbital in the liver of both species. A low constitutive level of PXR mRNA was also detected by RT-PCR in the lung of rabbit but not in rat. However, also in this case, their expressions were not altered by the administration of strong CYP 3A inducers such as clotrimazole or a mixture of dexametasone plus pregnenolone 16alpha-carbonitrile for the rat and rifampicin or phenobarbital for the rabbit. For the first time, it was demonstrated by RT-PCR that rat lung expresses CYP 3A2, 3A9, 3A18 and 3A23 whereas the rabbit lung expresses the CYP 3A6, the only CYP 3A isoform identified in the rabbit so far. However, notwithstanding the differences observed in the constitutive presence of PXR and CYP 3A transcripts in both species, the above mentioned treatments did not affect in their lungs, unlike their livers, neither the anti-rat 3A immunoreactive proteins nor the CYP 3A marker 7-benzyloxyquinoline O-debenzylase and the 6beta-testosterone hydroxylase activities. The results obtained indicate that the role of CAR and PXR in the lung of rat and rabbit is different from that observed in the liver or other extrahepatic tissues where the induction of the CYP 2B and CYP 3A isoforms is regulated by these receptors.
[Show abstract][Hide abstract]ABSTRACT: In the last 10 years, there is an increasing interest in selenium (Se) because of its environmental, biological, and toxicological importance, and in particular, because of its antioxidant properties. However, inspite of extensive studies, the optimal concentration of Se to be used for its beneficial effects in not yet known. In addition, the mechanisms of Se antioxidant property require further study. We report on the effects of various mutagens/carcinogens such as azoxymethane, methylmethanesulphonate, and hydrogen peroxide on Chinese V79 hamster cells, in presence of sodium selenite in the concentration of 0.5 microM. We found that Se reduced the genotoxic effect of these mutagens/carcinogens. We also investigated enzymatic activities of glutathione peroxidase, catalase, superoxide dismutase, and glutathione S-transferase, in order to understand the Se involvement in the detoxification of free radicals. Sodium selenite increased the activities of glutathione peroxidase and catalase.
No preview · Article · Mar 2003 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
[Show abstract][Hide abstract]ABSTRACT: Magnesium is a microelement that is essential for biological functions and particularly for cellular metabolism. It has a central role in protein, lipid, carbohydrate, and nucleic acid synthesis, and it is important for muscular physiology and nerve excitability. Magnesium has an important role in the stability of biological membranes, it controls immune phenomena, and it activates over 300 enzymes. However, the mechanism of action of magnesium salts has not been well investigated and, in particular, its antimutagenesis properties and its effects in the detoxification of free radicals need further study. We investigated the effect of magnesium chloride, sulphate, carbonate, and oxide on the yeast Saccharomyces cerevisiae D7 strain, to evaluate their ability to protect against genotoxic damage. We found that magnesium salts induced antimutagenic effects in the cells harvested in the logarithmic phase by decreasing the induction of hydrogen peroxide. This, however, did not occur in the stationary phase. We also studied calcium salts of the type corresponding to those of magnesium and their protective role against the oxidative damage of free radicals and enzymatic activities, such as catalase, glutathione peroxidase, and superoxide dismutase, which are involved in antioxidative defenses.
No preview · Article · Feb 2000 · Journal of Environmental Pathology Toxicology and Oncology
[Show abstract][Hide abstract]ABSTRACT: Cancer development is a multistage process wherein mutational events play an important role. Various antimutagen components, in particular magnesium and selenium, have been reported to have anticarcinogenic properties. These two oligoelements display different behaviors according to their concentrations. The different effects of magnesium and selenium depend on the different mechanisms of cell absorption. The importance of antimutagenesis studies in cancer prevention is reported and a review of the basic mechanisms operative in antimutagenesis, including some data on known antimutagens, is made.
No preview · Article · Feb 1996 · Journal of Environmental Pathology Toxicology and Oncology
[Show abstract][Hide abstract]ABSTRACT: The effects of the antimutagenic flavoring cinnamaldehyde on the induction of HGPRT- mutants by methyl methanesulfonate (MMS), N-nitroso-N-methylurea (MNU), ethyl methanesulfonate (EMS) and UV light was investigated in the Chinese hamster V79 cell line. Cinnamaldehyde did not show any mutagenic or toxic effects in this experimental system by itself and did not modify mutation frequency when given to cells simultaneously with chemical mutagens. Under these conditions, the cytotoxicity of MMS, but not that of MNU and EMS, was increased. Cell viability was also reduced in MNU-, EMS-, or UV light-pretreated cells when they were postincubated in the presence of cinnamaldehyde. Moreover, cinnamaldehyde reduced the frequency of mutations induced by MMS but not by the other mutagens. The results obtained suggest that cinnamaldehyde inhibits some cellular function(s) promoting the repair of a variety of different cytotoxic lesions. At the same time, stimulation by cinnamaldehyde of an error-free DNA repair mechanism acting on MMS-induced mutagenic damage was indicated.
No preview · Article · Jul 1994 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
[Show abstract][Hide abstract]ABSTRACT: Spermine is a polyamine found in bacteria, animal, and plant tissues. It is involved in a variety of biological processes, and its interaction with DNA stabilizes the secondary structure of the double helix. Spermine is one of the first reported antimutagens, reducing the mutation rate in several prokaryotic test systems, while in eukaryotic organisms conflicting results have been obtained. In light of the significant antimutagenic effect of spermine, it is important to evaluate its activity in mammalian cells in culture. The present study was undertaken to evaluate the ability of spermine to suppress the level of HGPRT- mutants induced by ethylmethanesulfonate, methylmethanesulfonate, and mitomycin C. Spermine reduced the mutation frequency induced by ethylmethanesulfonate and methylmethanesulfonate but did not affect survival; with mitomycin C survival was reduced but mutation rate was not influenced.
No preview · Article · Jan 1994 · Environmental and Molecular Mutagenesis
[Show abstract][Hide abstract]ABSTRACT: The activity of cinnamaldehyde (CIN), a bioantimutagen in bacterial systems, was tested in the D7 strain of yeast Saccharomyces cerevisiae. Yeast cells were UV-irradiated and post-incubated in liquid growth medium for 2 and 4 h with different concentrations of cinnamaldehyde. During the post-incubation period, DNA-damage-specific functions may be induced. This in turn may affect the genotoxicity and in fact a weak decrease in UV-induced convertant and revertant frequencies was observed after 4 h of post-incubation. The presence of CIN in the growth medium increased the UV-induced gene conversion and reversion. The addition of cycloheximide abolished this effect. To evaluate the CIN effect on protein synthesis, extracts of cells UV-treated and post-incubated for 2 h in the presence of 35S-methionine were performed. SDS-gel electrophoresis demonstrated the inhibitory effect of CIN on a UV-specific protein. This work suggests that CIN might interfere with DNA-damage-inducible systems although it did not exert an antimutagenic activity in our experimental conditions.
Full-text · Article · Jun 1992 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
[Show abstract][Hide abstract]ABSTRACT: Incubation of methoxypsoralen (5-MOP) in the presence of diploid yeast cells (Saccharomyces cerevisiae) before UV-A exposure leads to an incubation-time dependent decrease of photoinduced genotoxic effects. The reduction in photoinduced genotoxicity is stronger in cells grown in the presence of 20% glucose and containing high levels of cytochrome P-450 than in cells grown in the presence of 0.5% glucose and containing undetectable levels of cytochrome P-450. Inhibition of P-450 activity by specific inhibitors, such as tetrahydrofuran and metyrapone, strongly affects the observed decrease in 5-MOP genotoxicity, indicating the involvement of P-450 in 5-MOP metabolism. As demonstrated by spectrophotometric and chromatographic (HPLC) analysis during incubation of 5-MOP with P-450 containing yeast cells, 5-MOP gradually disappears from the cell supernatant of the incubation mixture. The reduction in the chromatographic peak corresponding to 5-MOP is accompanied by the appearance of a new peak that probably corresponds to a metabolite. As shown by the use of P-450 specific inhibitors, the metabolite appears to be due to P-450 mediated 5-MOP metabolisation. Its UV absorption spectrum suggests an alteration of the pyrone moiety of the 5-MOP molecule.
No preview · Article · Dec 1991 · Photochemistry and Photobiology
[Show abstract][Hide abstract]ABSTRACT: Treatment of CD1 mice with acetone raised activities of hepatic microsomal p-nitrophenol hydroxylase, ethoxycoumarin de-ethylase, acetone hydroxylase and diethylnitrosamine de-ethylase (DENd) several-fold. P-450IIE1-linked acetone hydroxylase showed the highest inducibility. In microsomes from acetone-pretreated mice the cytochrome b5 and P-450 content was nearly doubled and their electrophoretic profile showed induction of a protein of Mr 53,000, probably P-450IIE1. Liver phase II enzymes were not affected by acetone treatment. Kinetic analyses of DENd were performed in control or acetone-induced microsomes and Km and Vmax were determined. Two distinctly apparent Km values (0.56 and 20.3 mM) were observed for DENd of control microsomes and at least 3 apparent Km values (0.05, 0.51, 8.4 mM) were observed in acetone-induced microsomes. Thus, acetone administration to mice induces a high-affinity form of DENd which can be important in vivo at low diethylnitrosamine (DEN) exposure as this enzyme functions when DEN concentration is below 0.1 mM.
No preview · Article · Jan 1991 · Toxicology Letters
[Show abstract][Hide abstract]ABSTRACT: The ability of vanadium compounds to induce genetic activity was investigated in D7 and D61M strains of Saccharomyces cerevisiae and in Chinese hamster V79 cell line.
In our previous work, ammonium metavanadate (pentavalent form, V5) induced mitotic gene conversion and point reverse mutation in the D7 strain of yeast. The genotoxicity was reduced by the presence of S9 fraction, which probably reduced pentavalent vanadium to the tetravalent form.
In the present study, vanadyl sulfate (tetravalent form, V4) induced no convertants and revertants in yeast cells harvested from stationary growth phase. With yeast cells from logarithmic growth phase, which contain high levels of cytochrome P-450, a significant increase in genetic effects was observed. Further experiments, performed by treating cells harvested from logarithmic growth phase in the presence of cytochrome P-450 inhibitors, indicated that the monooxygenase system influenced the genotoxicity of metavanadate while the genetic activity of vanadyl remained unaffected. Aneuploidy effect in the D61M strain of Saccharomyces cerevisiae was induced by either V5 or V4, confirming that vanadium compounds are potentially antitubuline agents in eukaryotic cells.
Although these compounds are very toxic in V79 cells, no mutagenic effect was observed in the presence or in the absence of S9 fraction.
No preview · Article · Jan 1991 · Teratogenesis Carcinogenesis and Mutagenesis