Cyto-genotoxicity of amphibole asbestos fibers in cultured human lung epithelial cell line: Role of surface iron

Abstract

The present investigations correlate the potentials of the reactive oxygen species (ROS) generation and the cyto-genotoxicity of amphibole asbestos fibers (amosite, crocidolite and tremolite) with their surface iron, under in vitro controlled conditions, using A549 cells (human lung epithelial cell line). The mobilizable surface iron was measured by Atomic Absorption Spectroscopy; the production of ROS was investigated using 2, 7 dichloro-dihydrofluorescein-diacetate (DCFH-DA) dye; for cytotoxicity assessment, the intracellular organelles specific damages were measured, using 3-(4, 5 dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide salt (MTT) assay; and, the genotoxic potential of amphibole fibers was determined by cytokinesis block micronucleus (CBMN) assay. In the study, highest amount of ROS was generated by crocidolite followed by tremolite and minimum with amosite. In MTT assay, the time- and concentration-dependent decrease in percent cell viability was recorded with all the three amphibole fibers, tremolite being most cytotoxic, followed by crocidolite, and then amosite. In genotoxicity assay, an increase in the frequency of micronuclei (MNi) in binucleated (BN) cells was observed, where crocidolite was most genotoxic, followed by tremolite, and amosite the least.The comparison of results depicts a clear trend of cyto-genotoxic potential paralleling the ROS generation, suggesting a definite role of oxidative stress in fiber-induced toxicity. However, amosite contains maximum surface iron (28%), followed by crocidolite (27%), and tremolite carrying least (as contaminant) or no iron, the mobilizable surface iron is maximum in crocidolite followed by amosite and is minimum in tremolite. The mobilizable iron somewhat corresponds with the ROS generation capacity of these fibers. This shows that the surface iron could be mainly responsible for amphibole asbestos-induced ROS toxicity; though it may not be the only factor responsible, other factors like shape and size etc., also play role in amphibole asbestos-induced toxicity.

Asbestos modulates thioredoxin-thioredoxin interacting protein interaction to regulate inflammasome activation

“…Asbestos-induced ROS generation has been shown to cause oxidative damage to mitochondrial and genomic DNA [21,22] and may modulate the activity/function of various signaling molecules, transcription factors and enzymes that are redox sensitive [11,21,23]. The high iron content as well as the valency state of iron on crocidolite asbestos fibers has been shown to facilitate Fenton reactions both intracellularly and extracellulary [24,25]. Mitochondrial generated superoxide can react with Fe 3+ ions on asbestos fibers to reduce it to Fe 2+ [25].…”

Titanium Dioxide Nanoparticles As Guardian against Environmental Carcinogen Benzo[alpha]Pyrene

“…Percentage cell viability was assessed using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay as described earlier [16]. In brief, the cells (1×10 4 ) were allowed to adhere for 24 h in 5% CO2 at 37°C and 20% humidity in 96-well culture plates.…”

Ameliorative Effects of Dimetylthiourea and N-Acetylcysteine on Nanoparticles Induced Cyto-Genotoxicity in Human Lung Cancer Cells-A549

“…The micronucleus assay was done as described earlier by us [44]. The cells were exposed to TiO 2 -NPs and MWCNTs (10 & 50 µg/ml) with or without DMTU (10 mM) and NAC (2 mM) for 24 h, then cells were washed and supplemented with cytochalasin B (3 µg/ml, Sigma)-containing medium and were incubated further for another 22 h to accomplished the nuclear division (22h-doubling time for A549 cell line).…”