Xenopus laevisOocytes as a Model System for Studying the Interaction Between Asbestos Fibres and Cell Membranes

Abstract

The mode of interaction of asbestos fibres with cell membranes is still debatable. One reason is the lack of a suitable and convenient cellular model to investigate the causes of asbestos toxicity. We studied the interaction of asbestos fibres with Xenopus laevis oocytes, using electrophysiological and morphological methods. Oocytes are large single cells, with a limited ability to endocytose molecular ligands; we therefore considered these cells to be a good model for investigating the nature of asbestos/membrane interactions. Electrophysiological recordings were performed to compare the passive electrical membrane properties, and those induced by applying positive or negative voltage steps, in untreated oocytes and those exposed to asbestos fibre suspensions. Ultrastructural analysis visualized in detail, any morphological changes of the surface membrane caused by the fibre treatment. Our results demonstrate that Amosite and Crocidolite-type asbestos fibres significantly modify the properties of the membrane, starting soon after exposure. Cells were routinely depolarized, their input resistance decreased, and the slow outward currents evoked by step depolarizations were dramatically enhanced. Reducing the availability of surface iron contained in the structure of the fibres with cation chelators, abolished these effects. Ultrastructural analysis of the fibre-exposed oocytes showed no evidence of phagocytic events. Our results demonstrate that asbestos fibres modify the oocyte membrane, and we propose that these cells represent a viable model for studying the asbestos/cell membrane interaction. Our findings also open the possibly for finding specific competitors capable of hindering the asbestos-cell membrane interaction as a means of tackling the long-standing asbestos toxicity problem.

On the mechanism of the electrophysiological changes and membrane lesions induced by asbestos fiber exposure in Xenopus laevis oocytes

“…In line with our previous study, crocidolite (Croc) exposure affected the electrical membrane properties of oocytes; specifically, the resting membrane potential (RP) and membrane resistance (R m ) were significantly reduced with respect to control (Ctrl), while the current amplitudes activated by both negative and positive voltage steps were increased 2 . Fig.…”

“…Considering that these molecular mechanisms are those that allow the fibers to enter the target cell cytosol and then the nuclear compartment to interfere with the DNA integrity and transcriptional activity, their knowledge is compelling in helping to find new therapeutic approaches for treating exposed subjects. We recently described Xenopus laevis oocytes as a suitable model for studying in detail, the interaction between asbestos fibers and biological cell membranes at the electrophysiological and morphological level 2 . We found that exposure of the oocyte cells to aqueous suspensions of amosite (brown asbestos) or crocidolite (blue asbestos), significantly affected their electrical membrane properties as well as the morphology of the cells, and proposed that the fibers, either by adsorbing onto the cell surface and/or traversing the membrane, somehow created a “pore” through which ion fluxes (most likely Cl − ) could occur to change the resting membrane potential and membrane resistance of the cells.…”

Iron oxide nanoparticles can cross plasma membranes

“…To learn more about the interactions of NPs with the plasma membrane of the oocytes, we have followed possible changes of its integrity due to exposure to Fe 3 O 4 NPs by Two Electrodes Voltage Clamp (TEVC). With a similar approach, Bernareggi and colleagues 38 have recently evaluated the effects of asbestos fibres on Xenopus oocyte membrane.…”

Synchrotron X-ray microscopy reveals early calcium and iron interaction with crocidolite fibers in the lung of exposed mice

“…It is believed that membrane damage allow the influx of extracellular Ca ions into the cell, where it complexes with phosphate groups, ultimately forming crystalline apatite (Trump et al, 1980). In the case of asbestos-induced calcification, it is not entirely clear how the fibers initially interact with cell membranes (Harington et al, 1975;Hill, 1982, 1983;Hesterberg et al, 1986;Malorni et al, 1990;Elferink and Kelters, 1991;Dopp et al, 2000;Nagai and Toyokuni, 2012;Bernareggi et al, 2015), nor is it known why the precipitates form intracellular deposits around asbestos fibers as earlier described by Brody and Hill (Brody and Hill, 1982).…”