Iron mobilization from asbestos by chelators and ascorbic acid

The ability of chelators and ascorbic acid to mobilize iron from crocidolite, amosite, medium- and short-fiber chrysotile, and tremolite was investigated. Ferrozine, a strong Fe(II) chelator, mobilized Fe(II) from crocidolite (6.6 nmol/mg asbestos/h) and amosite (0.4 nmol/mg/h) in 50 mM NaCl, pH 7.5. Inclusion of ascorbate increased these rates to 11.4 and 4.9 nmol/mg/h, respectively. Ferrozine mobilized Fe(II) from medium-fiber chrysotile (0.6 nmol/mg/h) only in the presence of ascorbate. Citrate and ADP mobilized iron (ferrous and/or ferric) from crocidolite at rates of 4.2 and 0.3 nmol/mg/h, respectively, which increased to 4.8 and 1.0 nmol/mg/h in the presence of ascorbate. Since ascorbate alone mobilized iron from crocidolite (0.5 nmol/mg/h), the increase appeared to result from additional chelation by ascorbate. Citrate also mobilized iron from amosite (1.4 nmol/mg/h) and medium-fiber chrysotile (1.6 nmol/mg/h). Mobilization of iron from asbestos appeared to be a function not only of the chelator, but also of the surface area, crystalline structure, and iron content of the asbestos. These results suggest that iron can be mobilized from asbestos in the cell by low-molecular-weight chelators. If this occurs, it may have deleterious effects since this could result in deregulation of normal iron metabolism by proteins within the cell resulting in iron-catalyzed oxidation of biomolecules.