[Tuberculosis in the dental office. Epidemiology, clinical view and prevention]. / Tuberculose in de tandartspraktijk. Epidemiologie, klinisch beeld en preventie.

The expectation that tuberculosis would be eliminated in the Netherlands by about 2030 has been negatively adjusted due to a variety of factors. The incidence of pulmonary and extrapulmonary tuberculosis has even increased. The risk for oral health care providers to be exposed to tuberculosis has also increased. A questionnaire among dentists revealed that knowledge concerning tuberculosis is limited. On the basis of a review of the literature, an overview is given of the pathways of tuberculosis infection, the immunology of tuberculosis, clinical signs of tuberculosis, resistance to tuberculosis, diagnostic tools for tuberculosis, and the therapy and prevention of tuberculosis. Emphasis is placed especially on manifestations of oral tuberculosis and the prevention of tuberculosis in dental practice.

[An inventory of knowledge on tuberculosis among dentists in the Netherlands]. / Inventarisatie van de kennis over tuberculose onder tandartsen in Nederland.

By the nature of his work, a dentist has a higher risk of tuberculosis infection than the average Dutch population. Thus, the question arises whether dentists do have sufficient knowledge on tuberculosis. In order to determine their knowledge, an inventory was conducted among a sample of dentists in the Netherlands. Analysis of the dentists' response to 19 correct or incorrect statements revealed that their knowledge level on tuberculosis was rather low, did not vary with regard to gender, and was independent of the region where they were practising and of their explicit medical interest. The dentists indicated a desire for education on tuberculosis.

DNA damage in human transitional cell carcinoma cells after exposure to the proximate metabolite of the bladder carcinogen 4-aminobiphenyl.

The DNA damage induced by N-hydroxy-4-acetylaminobiphenyl (N-OH-AABP), the proximate carcinogenic metabolite of the human bladder carcinogen 4-aminobiphenyl (ABP), was examined in human transitional cell carcinoma (TCC) cells after exposure to the chemical in vitro. 32P-postlabeling analysis of TCC cultures exposed to N-OH-AABP revealed a minor adduct identified as 3-(deoxyguanosin-N2-yl)-4-acetylaminobiphenyl (dG-N2-AABP) based on comparison of the HPLC and TLC mobility of the product with the synthetic standard. An adduct with the same chromatographic properties was also detected on postlabeling analyses of calf thymus DNA bound to N-OH-AABP by incubation with horseradish peroxidase and hydrogen peroxide. Detection of dG-N2-AABP, which contains the acetyl moiety, suggests that N-acetoxy-4-acetylamino-biphenyl might be formed as a reactive intermediate and could conceivably arise by a free-radical-mediated reaction of N-OH-AABP with endogenous peroxidases. The radical intermediates could also form reactive oxygen species (ROS). To test this possibility, TCC cultures were exposed to N-OH-AABP and the formation of ROS was measured using 2,7-dichlorofluorescein (DCF) fluorescence assay. TCC cultures exposed to N-OH-AABP showed a dose-dependent increase in the ratio of DCF/DNA fluorescence compared to the untreated controls. Formation of ROS was inhibited by butylated hydroxyanisole (BHA). Furthermore, oxidative DNA damage resulting from ROS was monitored by measurement of 8-oxoguanine products by immunochemical staining and the TCC cells treated with N-OH-AABP revealed a characteristic staining. These results suggest that N-OH-AABP caused oxidative DNA damage as well as bulky covalent adducts in urothelial DNA, possibly involving endogenous peroxidases. These findings show that human uroepithelial cells, which are the target cell types in vivo for arylamine-induced cancers, are metabolically capable of activating these proximate carcinogenic metabolites of arylamines, and these reactions might play a determinate role in the genotoxicity of these environmental carcinogens.

Role of TP53 in repair of N-(deoxyguanosin-8-yl)-4-aminobiphenyl adducts in human transitional cell carcinoma of the urinary bladder.

The global genomic repair of DNA adducts was examined in human papillary transitional cell carcinoma (TCC) cell lines after exposure to N:-hydroxy-4-acetylaminobiphenyl (N-OH-AABP), the proximate carcinogenic metabolite of the human bladder carcinogen 4-aminobiphenyl (ABP). (32)P-post-labeling analysis of TCC cultures exposed to N-OH-AABP revealed a major adduct, identified as the 3',5'-bisphosphate derivative of N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-ABP). The amount of adduct formation in TCC10 was dependent upon the dose and the duration of exposure and ranged between 1 and 5 adducts/10(7) nucleotides. To test if p53 regulates repair of the dG-C8-ABP adduct in genomic DNA, an isogeneic set of cell lines was obtained by infection of the TCC10 cultures with a retroviral construct expressing a trans-dominant mutant of p53, namely a Val-->Ala mutation at codon 143. The TDM143-TCC10 line expressing the mutant form of p53 was selected. The rate of repair of dG-C8-ABP was compared between TCC10 and TDM143-TCC10 cultures after treatment with 15 microM N-OH-AABP. The rate of disappearance of the adduct was monitored over a period of time after chemical treatment. (32)P-post-labeling analysis of dG-C8-ABP in parental TCC10 showed its rapid removal, the majority of adducts disappearing within 48 h. In contrast to TCC10, TDM143-TCC10 was relatively slower in removal of dG-C8-ABP. After 24 h DNA repair TDM143-TCC10 showed an approximately 3-fold greater amount of dG-C8-ABP compared with TCC10. These results imply that p53 plays a role in the repair of ABP adducts and that in p53 null cells the unrepaired DNA damage could cause accumulation of mutations, which might contribute to increased genomic instability and neoplastic progression.

Different combinations of genetic/epigenetic alterations inactivate the p53 and pRb pathways in invasive human bladder cancers.

Inactivation of both the pRb (pRb-cyclin D1/cyclin-dependent kinase 4/6-p16) and p53 (p53-p21(WAF1)-p14(ARF)) pathways is thought to be essential for immortalization in vitro and malignant transformation in vivo. We identified different combinations of pRb and p53 pathway alterations in 12 invasive transitional cell carcinomas (TCCs) and addressed the functional significance of the different combinations observed. Results showed four combinations of alterations including -pRb/-p53 (ie., pRb inactivated in the pRb pathway and p53 inactivated in the p53 pathway; four TCCs), -p16/-p53 (four TCCs), -p16/-p21(WAF1) (one TCC), and -p16/ -p14(ARF) (two TCCs). These groups include two new combinations (ie., -p16/-p53 and -p16/-p21(WAF1)) not reported previously for TCCs. An alteration in the key components of the p53 pathway was not detected in one invasive TCC that had inactivated p16. Note that all four TCCs with inactivated pRb had mutant p53; thus, the combinations of -pRb/ -p21(WAF1) and -pRb/-p14(ARF) were not observed. Only two of eight TCCs with altered p16 had concomitant p14(ARF) loss, demonstrating that simultaneous inactivation of these two 9p21INK4a tumor suppressor genes is not obligatory. To determine the biological phenotypes of TCCs with different combinations of pRb and p53 pathway alterations, their downstream responses to gamma radiation were studied in vitro. As expected, none of eight TCCs with mutant p53 responded to gamma radiation by elevation of p53, p21(WAF1), or mdm2 or by cell cycle arrest. Only two of four TCCs with wild-type p53 and wild-type pRb (the combination of -p16/-p14(ARF)) showed normal downstream responses to gamma radiation and underwent cell cycle arrest. Two TCCs with wild-type pRb and wild-type p53 (the combination of -pl6/-p21(WAF1) and one TCC with -p16) failed to show cell cycle arrest in response to radiation. This was attributed to the absence of p21(WAF1) in one TCC. In summary, these data support a model of invasive bladder cancer pathogenesis in which both the pRb and p53 pathways are usually inactivated and the biology of the tumor is impacted by the mechanism of their inactivations.

Replicative senescence in human uroepithelial cells.

PURPOSE: Normal human uroepithelial cells (HUCs) proliferate rapidly in culture during early passage and then spontaneously undergo replicative senescence. We previously reported that the cyclin D1-CDK4/6 inhibitor, p16INK4a, is elevated at senescence in HUCs. Hence, we proposed that p16INK4a may play a critical role in mediating senescence in this cell type. In the current study, we further characterized the senescent state in HUCs. We also tested the possible roles of changes in other cell cycle proteins, including p53, p21WAF1, pRb, and cyclin D1 in HUC senescence. METHODS: Normal HUCs cultured from explants of ureteral mucosa were used for these studies. Senescence associated-beta-galactosidase activity (SA-beta-gal) was used to identify cells in senescence. Flow cytometric analysis was used to determine changes in cell cycle distribution at senescence. Response of cells to serum stimulation was determined by Northern analysis of c-fos. Western analysis was used to assess changes in p53, p21WAF, p16INK4a, cyclin D1 and plasminogen activator inhibitor-1 (PAI-1) levels at senescence. RESULTS: beta-gal-positive HUCs were blocked at G1/S in senescence and failed to show c-fos induction in response to serum stimulation. As previously reported, senescent HUCs also showed elevated p16INK4a. However, unlike human fibroblasts, neither p53 nor p21WAF1 elevation accompanied HUCs senescence. PAI-1 levels were also not elevated in HUC senescence. CONCLUSION: These findings support a model in which elevation of p16INK4a, but not p53 or p21WAF1 plays a critical role in HUC replicative senescence. These findings elucidate the tumor suppressor mechanism of p16INK4a and the frequent loss of either p16INK4a or pRb in invasive human bladder tumors.