Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 3: Depletion of antioxidant defenses.

The asbestiform fibrous silicate balangeroite exhibits cytotoxic and oxidative properties similar to those exerted by crocidolite asbestos. In human lung epithelial cells A549, balangeroite, like crocidolite, inhibited the pentose phosphate pathway (PPP), one of the main antioxidant intracellular tools; this inhibition was exerted also when PPP was activated by the redox-cycling compound menadione. PPP inhibition may be accounted for by the inhibition of its rate-limiting enzyme, glucose-6-phosphate dehydrogenase (G6PD). Reduced glutathione (GSH), the most important intracellular antioxidant molecule, was decreased by both balangeroite and crocidolite incubation. This effect was not related to any increased content of oxidized glutathione, or to any enhanced efflux of glutathione, suggesting that balangeroite fibers, like crocidolite, might favor the reaction of GSH with other molecules.