Distinct subtypes of urinary bladder epithelial cells with inducible and non-inducible cytochrome P450 1A1.
ABSTRACT Cultured primary porcine urinary bladder epithelial cells (PUBEC) represent an adequate and easy to handle in vitro system for studies of urothelial toxicity. PUBEC maintain in vivo-like metabolic activities and physiological functions. They express inducible cytochrome P4501A isoenzymes, which are of particular relevance, since they contribute to activation of bladder carcinogens. A possible drawback of PUBEC is their isolation from common domestic pigs that do not represent an inbred strain. In order to further establish PUBEC as a standard in vitro toxicity test system we analysed possible interindividual differences in CYP1A1 inducibility. Interestingly, we observed by flow cytometry that PUBEC obtained from individual pigs consist of two distinct subpopulations with inducible and non-inducible cells. A strong, concentration-dependent CYP1A1 induction was observed in the responsive subpopulation when incubated with benzo[a]pyrene (B[a]P) in a concentration range between 1 and 10 muM. In contrast, no CYP1A1 induction was obtained in the non-responsive subpopulation up to the highest tested concentrations of 100 muM. The fraction of responsive cells showed large interindividual differences ranging from 10 to 65% of the total cell number. For practical purposes it might be reasonable to analyse pools of PUBEC from five pigs which substantially reduce batch to batch variability. In conclusion, we have identified two functionally distinct subpopulations of urinary bladder epithelial cells. It will be interesting to study whether the CYP1A inducible subtype is more susceptible to bladder carcinogens.
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ABSTRACT: Aromatic amines have been shown to cause bladder cancer. However, epithelial cells of the urinary bladder, cells of origin of bladder cancer, may be exposed to numerous substances besides aromatic amines. In the present study, we analysed possible interactions between the aromatic amines 4-aminobiphenyl (4-ABP) as well as 2-naphthylamine (2-NA) and the polycyclic aromatic hydrocarbon benzo[a]pyrene (B[a]P). For this purpose we incubated primary porcine urinary bladder epithelial cells (PUBEC) with concentrations of 1 to 50 microM 4-ABP with and without co-exposure to B[a]P. As expected B[a]P increased mRNA expression of cytochrome P450 1A1 (CYP1A1), whereas 4-ABP had no effect. However, when co-exposed 4-ABP enhanced the induction of CYP1A1 by B[a]P. This result was confirmed by Western blot analysis of CYP1A1 protein expression. A similar effect as for CYP1A1 was also observed for cyclooxygenase-2 (COX-2) and UDP-glucuronosyltransferase 1 (UGT1). Next, we studied co-exposures of 2-NA and B[a]P. Similar as for 4-ABP also 2-NA enhanced B[a]P-mediated induction of CYP1A1. Our results demonstrate that some aromatic amines may enhance the influence of B[a]P on Ah receptor-dependent genes.Archives of Toxicology 01/2009; 82(12):973-80. · 5.22 Impact Factor
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ABSTRACT: Epithelial tissue lining the inner side of the urinary bladder is the most common target for bladder cancer-related diseases. Bladders of freshly slaughtered pigs were utilised for a comprehensive analysis of the proteome and phosphoproteome of bladder epithelial cells. Following protein separation by 2-D gel electrophoresis and identification by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) the first proteome and phosphoproteome maps of pig urinary bladder epithelial cells (PUBEC) were established. A total of 120 selected protein spots were identified. By using the La(3+) enrichment method further developed in our laboratory we identified 31 phosphoproteins with minimal contamination by non-phosphopeptides. The 2-DE map of pig urothelial cells may prove as a useful tool for studies on uroepithelial biology, and the analysed phosphoproteins expression pattern, together with the whole cell proteome, will be helpful for identifying the proteins involved in bladder-related diseases.Electrophoresis 12/2011; 32(24):3600-11. · 3.26 Impact Factor
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ABSTRACT: Polycyclic aromatic hydrocarbons (PAHs) are associated with occupational exposure and urban atmospheric pollution. Determination of the genotoxic properties of these compounds is thus of outmost importance. For this purpose a variety of cellular models have been widely used. Reliable results can however only be obtained with models reflecting the specific sensitivity of different organs towards PAHs. In this work, we compared the response to benzo[a]pyrene in cell lines from human lungs (A549) and bladder (T24); two important target organs for PAHs-induced cancer. Human hepatocytes (HepG2) were used as a reference, although liver is not a concern for PAHs carcinogenesis. Adducts arising from the ultimate diol-epoxide metabolite of B[a]P, BPDE, were found to be produced in a dose-dependent manner in HepG2. BPDE DNA adducts were not detected in T24 and in A549 their formation was found to be most efficient at the lowest concentration studied (0.2 µM). These results are probably explained by differences in induction and activity of phase I metabolization enzymes, as well as by proteins eliminating the B[a]P epoxide in A549. In addition to BPDE adducts, oxidative DNA damage, namely strand breaks and oxidized purines were measured and found to be produced only in minute amounts in all three cell lines. In summary, our results emphasize the large differences in the response of cells originating from different organs. Our data also point out the importance of carefully selecting the doses used in in vitro toxicological experiments. The example of A549 shows that working at high doses may lead to an underestimation of the risk. Finally, the choice of method for evaluating genotoxicity appears to be of crucial importance. The comet assay does not seem to be the best method for a compound like B[a]P which induces stable adducts causing limited oxidative damage.PLoS ONE 01/2013; 8(11):e78356. · 3.53 Impact Factor