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Biomedical subjects

M Castegnaro

Publications and source records attributed to M Castegnaro.

At least 55 records · Page 3Linked to original sources
PubMed1992

Expression of pulmonary cytochrome P4501A1 and carcinogen DNA adduct formation in high risk subjects for tobacco-related lung cancer.

Cigarette smoking is the strongest risk factor for lung cancer (LC), but genetically determined variations in pulmonary metabolism of tobacco-derived carcinogens may affect individual risk. Results from a case-control study on LC patients demonstrated the pronounced effect of tobacco smoke on pulmonary xenobiotic metabolism and prooxidant state, and suggested the existence of a metabolic phenotype at higher risk for tobacco-associated LC: LC patients who were recent smokers had significantly induced BP-3-hydroxylase (AHH) and ethoxycoumarin O-deethylase (ECDE) activities in lung parenchyma, when compared with smoking non-cancer patients. In recent smokers, lung AHH activity was positively correlated with the level of tobacco smoke-derived DNA adducts as determined by 32P-postlabelling. Pulmonary AHH activity also showed a good correlation with the intensity of immunohistochemical staining for cyt. P4501A by a monoclonal Ab in lung tissue sections: smoking and peripheral type of lung cancers were positively related to high levels of this cyt. P450 species, probably reflecting high rates of induction. These results suggest that high pulmonary CYP1A1 expression (controlling in part carcinogen DNA-adduct formation) in tobacco smokers, appears to be associated with LC risk. High risk subjects may thus be identifiable through genotyping assays for CYP1A1 polymorphism.

Aryl Hydrocarbon Hydroxylases↗
PubMed1992

Carcinogen metabolism in human lung tissues and the effect of tobacco smoking: results from a case--control multicenter study on lung cancer patients.

Cigarette smoking is the strongest risk factor for lung cancer, but genetically determined variations in the activities of pulmonary enzyme that metabolize tobacco-derived carcinogens may affect individual risk. To investigate whether these enzymes (e.g., CYP1A-related) can serve as markers for carcinogen-DNA damage, lung tissue specimens were taken during surgery from middle-aged men with either lung cancer or non-neoplastic lung disease. Phase I [aryl hydrocarbon hydroxylase (AHH), ethoxycoumarin O-deethylase (ECOD)] and phase II (epoxide hydrolase, UDP-glucuronosyltransferase, glutathione S-transferase) enzyme activities, glutathione and malondialdehyde contents were determined in lung parenchyma and/or bronchial tissues; some samples were also analyzed for DNA adducts, using 32P-postlabeling. The data were then analyzed for the following: a) differences in metabolic profiles between bronchial and parenchymal lung tissue; b) the effect of recent exposure to tobacco smoke on enzyme inducibility and benzo[a]pyrene metabolism; c) differences in enzyme inducibility between lung cancer and non-lung cancer patients; d) the effect of smoking on metabolism of mutagens in vitro; e) pulmonary DNA adduct levels and AHH activity in lung parenchyma of smokers and ex-smokers; f) lipid peroxidation products in lung tissue from lung cancer and non-lung cancer patients, as related to smoking habits and degree of airway obstruction; and g) prognostic value of AHH pulmonary activity in lung cancer patients. The results demonstrate a pronounced effect of tobacco smoke on pulmonary metabolism of xenobiotics and prooxidant state and suggest the existence of a metabolic phenotype at higher risk for tobacco-associated lung cancer.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1991

Genotoxic activity of potassium permanganate in acidic solutions.

Potassium permanganate (KMnO4) combined with sulfuric acid is a strongly oxidizing mixture which has been recommended for the destruction and the decontamination of various mutagens/carcinogens in the publication series of the International Agency for Research on Cancer. Evaluation of the genotoxicity of 4 potassium permanganate solutions was performed using a microtechnique of the Ames test with the tester strains TA97, TA98, TA100 and TA102 with and without metabolic activation. Presence of direct-acting mutagens was detected in all the samples with the tester strain TA102 without S9 mix (163-357 revertants/microliters of the solutions). Three samples containing either acetone or ethanol as an organic solvent also induced a mutagenic response on tester strain TA100 without S9 mix (167-337 revertants/microliters). In addition, DNA damage in human peripheral blood lymphocytes was also measured for one of the mixtures by a new technique: the single-cell gel assay (SCGA). A sample with no organic solvent induced DNA damage in human lymphocytes with a dose-response relationship as determined by SCGA. The major mutagenic agent generated by the permanganate solutions was found to be manganese ion (Mn2+). Both manganese sulfate (MnSO4) and manganese chloride (MnCl2) gave mutagenic dose-response relationships on tester strain TA102 without S9 mix. The mutagenic potencies were 2.8 and 2.4 revertant/nmole for MnSO4 and MnCl2 respectively. MnCl2 also induced DNA damage in human lymphocytes as determined by the SCGA. The genotoxic effects of KMnO4 in acidic conditions were probably mediated by the conversion of MnO4- to Mn2+. KMnO4 in alkaline solutions did not produce mutagenic species and may offer an alternative for the degradation of genotoxic compounds.

Biotransformation↗
PubMed1991

32P Postlabelling analysis of urinary mutagens from smokers of black tobacco implicates 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) as a major DNA-damaging agent.

When mutagens extracted from the urine of two smokers of black tobacco were reacted with DNA in vitro in the presence of a metabolic activation system, several DNA adducts were detected by 32P-postlabelling analysis. Some of these adducts were also visible, but only faintly, on the autoradiogram for a non-smoker's urine. DNA adducts produced in vitro by 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline or 2-amino-1-methyl-6-phenylimidazo[3,5-b]pyridine could not account for the adduct pattern produced by the urinary mutagens. However, three or four 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-related DNA adducts were present among the five or six adducts observed for smokers in the autoradiograms of urinary mutagen-adducted nucleotides. Mutagenicity testing combined with HPLC fractionation of urinary extracts also supported the postlabelling data which implicates PhIP as a mutagen in the urine of smokers of black tobacco.

Chromatography, High Pressure Liquid↗
PubMed1991

Comparison of pulmonary DNA adduct levels, measured by 32P-postlabelling and aryl hydrocarbon hydroxylase activity in lung parenchyma of smokers and ex-smokers.

In order to compare pulmonary DNA adducts and aryl hydrocarbon hydroxylase (AHH) activity, we have measured these two parameters in non-neoplastic surgical lung parenchymal samples from four ex-smokers and 19 smokers, out of 20 patients operated for lung cancer, and three for nonmalignant lung diseases. DNA adducts were determined by scintillation counting after 32P-postlabelling analysis. The microsomal fractions of the same lung specimen were assayed for AHH activity by a fluorometric method. Autoradiograms of DNA adducts found in lungs of smokers revealed two distinct diagonal radioactive zones that were absent in ex-smokers. The smokers had significantly higher levels (1.68-13.4 DNA adducts/10(8) nucleotides; mean +/- SD 5.38 +/- 3.19) than ex-smokers (0.23-2.21; 1.09 +/- 0.84). AHH activity in smokers ranged from 0.01 to 0.69 pmol/min/mg. This activity was significantly (P less than 0.05) higher in smokers (0.26 +/- 0.26) who had smoked until 1 week before surgery than in those who had stopped smoking for greater than 7 days (0.11 +/- 0.11). A positive linear correlation between DNA adduct levels and AHH activity (r = 0.69; P less than 0.001; n = 19) was found in smokers. This relationship could explain why AHH inducibility appears to be a crude marker for lung cancer risk in smokers.

Adult↗
PubMed1991

Ochratoxin A in human blood in relation to Balkan endemic nephropathy and urinary tract tumours in Bulgaria.

Ochratoxin A is suspected of being one of the etiological agents responsible for Balkan endemic nephropathy and the associated urinary tract tumours. Contamination of cereals by this mycotoxin has been found to be more frequent in areas of endemic nephropathy than in areas where the disease is absent. As ochratoxin A binds to serum albumin, it should be detectable in biological fluids from exposed populations. A survey was thus conducted to determine the occurrence of ochratoxin A in blood from people living in the endemic area who were either affected or unaffected by the two diseases and in blood from people living in control regions where these diseases do not occur. Blood samples were collected in 1984, 1986, 1989 and 1990. Ochratoxin A was found more frequently and at higher levels in blood from patients with Balkan endemic nephropathy and/or urinary tract tumours than in blood from unaffected people from endemic and control areas. These findings suggest further that ochratoxin A is involved in the etiology of the two diseases.

Balkan Nephropathy↗
PubMed1991

Human ochratoxicosis in France.

The prevalence of human ochratoxicosis in France is being determined using serum and plasma collected from apparently healthy people. The analytical method is based on the partition coefficient of ochratoxin A in aqueous and organic solvents, according to pH. High-performance liquid chromatography and spectrofluorimetry are used for detection and quantification (limit of detection, greater than 0.2 ng/ml). The presence of ochrotoxin A is confirmed by the action of carboxypeptidase to yield ochratoxin alpha or by derivatization of ochratoxin A with boron trifluoride. The significance of the interim values obtained and the number of positive samples is discussed. A comparison with the distribution of known values in Germany and Scandinavia could be helpful in risk assessment with a view to prevention.

Chromatography, High Pressure Liquid↗
PubMed1991

Concentrations of ochratoxin A in the urine of endemic nephropathy patients and controls in Bulgaria: lack of detection of 4-hydroxyochratoxin A.

Ochratoxin A has been detected more frequently and at higher levels as a contaminant in staple food consumed by subjects affected by Balkan endemic nephropathy or urinary tract tumours in the Vratza district (Bulgaria) than in samples from control populations in and outside the endemic area. Serum from patients with Balkan endemic nephropathy also contained ochratoxin A more frequently and at higher levels than serum from controls. Metabolic phenotyping of subjects in the Vratza district with debrisoquine revealed a preponderance of extensive metabolizers among subjects at high risk for Balkan endemic nephropathy. In rats, ochratoxin A is metabolized to 4-hydroxyochratoxin A, and rat strains shown to be poor or extensive metabolizers of debrisoquine were also poor or extensive metabolizers of ochratoxin A. In order to determine whether the metabolic phenotype for debrisoquine also parallels that of ochratoxin A in humans, a sensitive method was developed for quantifying ochratoxin A and its 4-hydroxy metabolite in human urine. This method was subsequently used to analyse urine from subjects who had previously been phenotyped for debrisoquine. Ochratoxin A was detected more frequently and at higher levels in urine from members of families affected by Balkan endemic nephropathy than in samples taken from subjects in control areas. No 4-hydroxyochratoxin A was found in any of these samples (detection limit, 15 ng/l urine). On the basis of results from human studies and animal models, the role of genetic polymorphism in drug oxidation and disease susceptibility is discussed briefly.

Animals↗
PubMed1991

Chromosomal alterations in lymphocytes of patients with Balkan endemic nephropathy and of healthy individuals after incubation in vitro with ochratoxin A.

The possible involvement of mycotoxins in chromosomal alterations in patients with Balkan endemic nephropathy (BEN) was investigated cytogenetically. Lymphocyte cultures from patients with BEN and from individuals from a nonendemic region were examined and compared with cultures from healthy people which had been incubated in vitro with noncytotoxic doses of ochratoxin A. Significantly increased numbers of various numerical and structural anomalies were found in patients with BEN. Chromosome X in female patients occurred in both monosomic and polysomic forms. A 'prosomization' effect was seen along the entire length of supernumerary X chromosomes, manifested by retarded contraction resembling early mitotic stages, with a comparably detailed band pattern. No other specific numerical or structural change was found consistently in BEN patients. Incubation of the lymphocytes of healthy people with ochratoxin A induced similar aberrations and prosomization. These findings may support the hypothesis that ochratoxin A is involved in the pathogenesis of BEN.

Balkan Nephropathy↗
PubMed1991

Characterization of the cytochrome P450 isozyme that metabolizes ochratoxin A, using metabolic inducers, inhibitors and antibodies.

The phenotypic pattern of drug biotransformation is determined by both host and environmental factors. Debrisoquine is a good probe for phenotyping individuals, as its metabolism is not affected by age, gender, smoking habits or alcohol intake. People with Balkan endemic nephropathy or with urinary tract tumours in endemic areas are more frequently extensive metabolizers of debrisoquine than are healthy people. This finding has led to studies of the possible relationship between the metabolism of ochratoxin A and its toxicity and carcinogenicity on experimental models. Ochratoxin A is metabolized mainly in the liver into R- and S-isomers of 4- and 10-hydroxyochratoxin A, and the reaction is catalysed by cytochrome P450 haemoprotein. Animal species that are genetically different in their capacity to metabolize debrisoquine differ similarly in their capacity to metabolize ochratoxin A: female DA rats that are poor metabolizers of debrisoquine also poorly metabolize ochratoxin A, as assayed by urinary excretion of both the parent compound and of 4-hydroxyochratoxin A. Ochratoxin A hydroxylase activity is low in DA rat liver (and kidney) but is inducible by phenobarbital and 3-methylcholanthrene; debrisoquine hydroxylase is not known to be inducible by enzyme inducers. The reaction of ochratoxin A hydroxylase thus resembles those induced by 3-methyl-cholanthrene and catalysed by cytochrome P450IA. Ochratoxin A hydroxylase activity was further characterized in the livers of B6 and D2 mice that had been treated with typical enzyme inducers. Ochratoxin A hydroxylase was weakly inducible by phenobarbital, 3-methyl-cholanthrene and 2,4,7,8-tetrachlorodibenzodioxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ochratoxin A and other mycotoxins in cereals from an area of Balkan endemic nephropathy and urinary tract tumours in Bulgaria.

The etiology of Balkan endemic nephropathy and urinary tract tumours in the rural population of the endemic regions remains unknown. As one hypothesis involves mycotoxins, a survey was carried out to investigate the possible involvement of the nephrotoxic mycotoxins ochratoxin A and citrinin. Recently, this survey was extended to screening for the presence of other mycotoxins--aflatoxins, citrinin, sterigmatocystin and zearalenone. A total of 524 samples of home-produced and home-stored beans and maize from the harvests of 1984, 1985, 1986, 1989 and 1990 were analysed. Ochratoxin A was found in samples from both endemic and nonendemic areas, but more of the samples from affected families were contaminated, and at higher levels, than those from unaffected households. Citrinin and aflatoxins B1 and G1 were also found more frequently in samples from endemic areas. These results support the theory that mycotoxins are involved in the etiology of Balkan endemic nephropathy and urinary tract tumours.

Aflatoxins↗