Abstract
BackgroundChrysotile is considered less harmful to human health than other types of asbestos fibers. Its clearance from the lung is faster and, in comparison to amphibole forms of asbestos, chrysotile asbestos fail to accumulate in the lung tissue due to a mechanism involving fibers fragmentation in short pieces. Short exposure to chrysotile has not been associated with any histopathological alteration of lung tissue.MethodsThe present work focuses on the association of small chrysotile fibers with interphasic and mitotic human lung cancer cells in culture, using for analyses confocal laser scanning microscopy and 3D reconstructions. The main goal was to perform the analysis of abnormalities in mitosis of fibers-containing cells as well as to quantify nuclear DNA content of treated cells during their recovery in fiber-free culture medium.ResultsHK2 cells treated with chrysotile for 48 h and recovered in additional periods of 24, 48 and 72 h in normal medium showed increased frequency of multinucleated and apoptotic cells. DNA ploidy of the cells submitted to the same chrysotile treatment schedules showed enhanced aneuploidy values. The results were consistent with the high frequency of multipolar spindles observed and with the presence of fibers in the intercellular bridge during cytokinesis.ConclusionThe present data show that 48 h chrysotile exposure can cause centrosome amplification, apoptosis and aneuploid cell formation even when long periods of recovery were provided. Internalized fibers seem to interact with the chromatin during mitosis, and they could also interfere in cytokinesis, leading to cytokinesis failure which forms aneuploid or multinucleated cells with centrosome amplification.
Highlights
Chrysotile is considered less harmful to human health than other types of asbestos fibers
Its clearance from the lung is faster than it is with amphibole fibers, for chrysotile asbestos fails to accumulate in the lung tissue due to a mechanism involving fibers fragmentation in short pieces
Multinucleation and apoptosis induction after chrysotile treatment Since this study focuses the interaction of chrysotile fibers with cells in culture, the most important aspect was to observe a large number of cells with internalized fibers independently of the fiber concentration in culture medium
Summary
Chrysotile is considered less harmful to human health than other types of asbestos fibers. Its clearance from the lung is faster and, in comparison to amphibole forms of asbestos, chrysotile asbestos fail to accumulate in the lung tissue due to a mechanism involving fibers fragmentation in short pieces. Amphibole fibers had been mostly used by the market in the past, until being associated with several serious health diseases They are causally related to the development of asbestosis, bronchial cancer, malignant mesothelioma of pleura and peritoneum, and, to a more limited extent, to various gastrointestinal, oropharyngeal and laryngeal cancers [1,2]. Its clearance from the lung is faster than it is with amphibole fibers, for chrysotile asbestos fails to accumulate in the lung tissue due to a mechanism involving fibers fragmentation in short pieces. According to Walker et al (1992) [6] this mechanism would involve direct and indirect effects: the physical interaction of fibers with target cells or the free radicals generation from the fiber surface acting directly on DNA and indirectly on inflammatory reactions
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