Analysis of Cell Cycle Disruptions in Cultures of Rat Pleural Mesothelial Cells Exposed to Asbestos Fibers (original) (raw)
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Oncogene, 2004
Exposure to asbestos fibers increases the risk of development of mesotheliomas and lung carcinomas, but not fibrosarcomas. We present data suggesting that resistance of fibroblasts to asbestos-induced carcinogenesis is likely to be connected with their lower ability to generate reactive oxygen species (ROS) in response to asbestos exposure and stricter control of proliferation of cells bearing asbestos/ROS-induced injuries. In fact, chrysotile (Mg 6 Si 4 O 10 (OH) 8) asbestos exposure (5-10 lg/cm 2) increased intracellular ROS and 8-oxo-guanine contents in rat pleural mesothelial cells, but not in lung fibroblasts. Simultaneously, moderate dosages of chrysotile and other agents increasing ROS levels (hydrogen peroxide, H 2 O 2 and ethyl-methanesulfonate, EMS) inhibited cell cycle progression, in particular G1-to-S transition, in fibroblasts, but not in mesothelial cells. The arrested fibroblasts underwent cell death, while the majority of chrysotile-treated mesothelial cells survived. The differences in cell cycle response to asbestos/ROS-induced injuries correlated with distinct activity of p53-p21 Cip1/Waf1 pathway in the two cell types. Chrysotile, H 2 O 2 and EMS caused p53 upregulation in both cell types, but mesothelial cells, unlike fibroblasts, showed no accumulation of p21 Cip1/Waf1. Of note, treatment with doxorubicin caused similar p53-dependent p21 Cip1/Waf1 upregulation and cell cycle arrest in both cell types. This suggests differential response of fibroblasts and mesothelial cells specifically to asbestos/ROS exposure rather than to all DNA-damaging insults.
Environmental and Molecular Mutagenesis, 1995
We report the effects of chrysotile and crocidolite asbestos, and glass and rock wool fibers (man-made vitreous fibers, MMVF) on the induction of binucleate cells in vitro. The response of human mesothelial cells (target cells in fiber carcinogenesis) and rodent cells was compared. Human primary mesothelial cells, MeT-5A cells (an immortalized human mesothelial cell line), and rat liver epithelial (RLE) cells were exposed to asbestos and MMVF samples of similar size range. Milled glass wool, milled rock wool, and titanium dioxide were used as non-fibrous particle controls. All four fiber types caused statistically significant increases in the amount of binucleate cells in human primary mesothelial cells and MeT-5A cells (in the dose range OS-5.0 pg/ cm'). Chrysotile and crocidolite asbestos were more effective (1.3-3.0-fold increases) than thin glass wool and thin rock wool fibers (1.3-2.2fold increases). However, when the fiber doses were expressed as the number of fibers per culture area, the asbestos and MMVF appeared equally effective in human mesothelial cells. In RLE cells, chrysotile was the most potent inducer of binucleation (2.9-5.0-fold increases), but the response of the RLE cells to crocidolite, thin glass wool, and thin rock wool fibers was similar to the response of the human mesothelial cells. No statistically significant increases in the number of bior multinucleote cells were observed in human primary mesothelial cells or RLE cells exposed to the non-fibrous dusts. In MeT-5A cells exposed to 5 pg/cm' of milled glass wool and milled rock wool, as well as in cultures exposed to 2 and 5 pg/crn' of Ti02, significant increases were, however, observed. Our results show that rodent cells respond differently to mineral fibers than human cells. The results also add evidence to the suggested importance of disturbed cell division in fiber carcinogenesis.
Cytotoxicity of oxidants and asbestos fibers in cultured human mesothelial cells
Free Radical Biology and Medicine, 1994
AbstractwThe authors investigated the mechanisms caused by oxidants (superoxide and hydrogen peroxide) and asbestos (amosite) fibers in human mesothelial cells. Immortalized human pleural mesothelial cells (MET 5A) were exposed in vitro to one of the following: hypoxanthine (100-200 #M) plus xanthine oxidase (10-20 mU/ml) as a superoxide-generating system, H202 (50/zM-5 mM); or amosite ( 1-100/zg/cm2). Cellular adenine nucleotide depletion, DNA single strand breaks, extracellular release of nucleotides, and their catabolites and lactate debydrogenase (LDH) were assessed as markers of cell damage after 4-6 h exposure to the oxidants or fibers. The effect of intracellular antioxidant enzymes and exogenous antioxidants on cell damage were investigated during oxidant and amosite exposure. Superoxide radical and H202 exposure resulted in the depletion of adenine nucleotides, accumulation of the products of nucleotide catabolism, induction of DNA single strand breaks, and extracellular LDH release. Amosite exposure did not cause nucleotide depletion or induction of DNA single strand breaks. Inactivation of the intraceIlular antioxidant enzymes glutathione reductase or eatalase augmented cell damage during H202 exposure but not during amosite exposure.
Mutation Research/Genetic Toxicology and Environmental Mutagenesis, 2004
Human mesothelial cells (HMC), the progenitor cells of asbestos-induced mesothelioma, are particularly sensitive to the genotoxic effects of asbestos, although the molecular mechanisms by which asbestos induces injury in HMC are not well known. The high susceptibility of HMC to simian virus 40 (SV40)-mediated transformation is assumed to play a causative role in the pathogenesis of mesothelioma. The aim of this study was to investigate the asbestos-induced DNA damage in cultured HMC and SV40-transformed HMC (MeT-5A) compared with their malignant counterparts, i.e. human mesothelioma cells (MSTO). The time-dependent initiation of DNA-strand breaks as well as the induction of oxidative DNA base modifications were key factors for investigation. HMC, MeT-5A and MSTO cells were exposed to chrysotile and crocidolite asbestos (3 g/cm 2 ) during different time periods (1-72 h). DNA damage was investigated by use of the Comet assay and alkaline
Mechanisms of asbestos-induced carcinogenesis
2011
Respiratory exposure to asbestos fibers has been associated with diffuse malignant mesothelioma (DMM) in humans. Despite advancements in the molecular analyses of human DMM and the development of animal models, the carcinogenic mechanisms of the disease remain unclear. There are basically three hypotheses regarding the pathogenesis of asbestos-induced DMM, which may be summarized as follows:
Pathogenesis of experimentally induced asbestos mesothelioma in rats
Cancer Letters, 1998
Fragments of parietal and visceral pleura were studied by total ®lms preparation, light microscopy and SEM at different times after intrapleural injection of asbestos in Wistar rats. Pleural rat mesothelium in histological slices consists normally of one layer of oblong cells. By SEM the cells are¯at and coated with microvilli of different lengths. In total ®lms the parietal mesothelium was composed of large polygonal cells covering intercostal spaces and small cells covering spaces over the ribs. In¯ammatory reaction and permanent pathological regenerative processes were observed in the mesothelium during 24 months after inoculation of asbestos ®bres. Different lesions which we regarded as preneoplastic or premesotheliomatous were observed against the background of or without these processes. They were diffuse irregular hyperplasia and proliferation of epithelium-like or ®broblast-like cells and focal nodous proliferates composed of such cells with various morphological structures. The number of thymidine-labelled cells was signi®cantly more inside the proliferates than in the surrounding tissue. They were con®rmed by SEM and histological slices of the same ®elds. Chronic pathological regeneration of pleural mesothelium could be the background against which preneoplastic lesions and mesotheliomas develop easily.