Acute toxicity and inflammatory effect of asbestos fibres in an in vitro model of human gastrointestinal tract

The inhalation of asbestos fibers is notoriously associated with the insurgence of pulmonary diseases (i.e., malignant mesothelioma, lung cancer). Furthermore, increasing evidence suggests that gastrointestinal malignancies may arise from the oral ingestion of asbestos fibers, since they may be released from asbestos-cement pipes resulting in the contamination of drinking water supplies. Nonetheless, the potential adverse effects associated with the ingestion of asbestos fibres are yet to be completely understood. In this regard, a very useful experimental model is represented by the human intestinal Caco-2 cell line, which has been extensively employed for in vitro toxicology studies on the intestinal barrier. Indeed, when cultured to confluence onto porous membrane inserts, Caco-2 cells undergo a spontaneous differentiation which promotes the formation of a polarized cellular monolayer with functional features of small intestinal enterocytes. Thus, we set up an in vitro model based on the intestinal Caco-2 differentiated cells, expressing mature enterocyte markers, to study the potential damaging effects of commercial Russian chrysotile asbestos fibres divided into two different length fractions (> or <5-μm). The cytotoxic and inflammatory effects of the chrysotile fibres was evaluated in comparison to UICC crocidolite, which is an amphibole asbestos commonly employed as a positive carcinogenic standard. Indeed, both chrysotile fibre fractions induced a significant degree of acute cytotoxicity, with results comparable to the well-known damaging effects of crocidolite. Furthermore, the <5-μm chrysotile fraction also promoted the transcriptional upregulation of several pro-inflammatory cytokines (i.e., IL-1β, IL-6, IL-8 and TNF-α). These preliminary results indicate that the adverse effects derived by the unwanted ingestion of asbestos fibres could be studied by means of the Caco-2 intestinal barrier mimicking model.