The Secretory Response of Rat Peritoneal Mast Cells on Exposure to Mineral Fibers

Background: Exposure to mineral fibers is of substantial relevance to human health. A key event in exposure is the interaction with inflammatory cells and the subsequent generation of pro-inflammatory factors. Mast cells (MCs) have been shown to interact with titanium oxide (TiO(2)) and asbestos fibers. In this study, we compared the response of rat peritoneal MCs challenged with the asbestos crocidolite and nanowires of TiO(2) to that induced by wollastonite employed as a control fiber. Methods: Rat peritoneal MCs (RPMCs), isolated from peritoneal lavage, were incubated in the presence of mineral fibers. The quantities of secreted enzymes were evaluated together with the activity of fiber-associated enzymes. The ultrastructural morphology of fiber-interacting RPMCs was analyzed with electron microscopy. Results: Asbestos and TiO(2) stimulate MC secretion. Secreted enzymes bind to fibers and exhibit higher activity. TiO(2) and wollastonite bind and improve enzyme activity, but to a lesser degree than crocidolite. Conclusions: (1) Mineral fibers are able to stimulate the mast cell secretory process by both active (during membrane interaction) and/or passive (during membrane penetration) interaction; (2) fibers can be found to be associated with secreted enzymes—this process appears to create long-lasting pro-inflammatory environments and may represent the active contribution of MCs in maintaining the inflammatory process; (3) MCs and their enzymes should be considered as a therapeutic target in the pathogenesis of asbestos-induced lung inflammation; and (4) MCs can contribute to the inflammatory effect associated with selected engineered nanomaterials, such as TiO(2) nanoparticles.