mordenite and Lung-Neoplasms

Respirable mineral fibers, such as asbestos, are known to cause pleural mesothelioma, pulmonary fibrosis, and bronchial carcinoma, often years after exposure. Erionite and mordenite, two mineral aluminosilicates (zeolites) with different toxicities, can be used as models to help understand asbestos toxicity. Erionite is carcinogenic, while mordenite is relatively benign. No iron is typically present in erionite or mordenite, but because of their ion-exchange properties they can acquire iron after inhalation. The iron is typically in the Fe(III) form and will need to be reduced prior to any Fenton activity. Lung lining fluid contains antioxidants, such as glutathione (GSH) and ascorbic acid (AA), which can reduce Fe(III) to Fe(II). In this study, we have compared the Fenton reactivity of Fe(III)-exchanged erionite and mordenite after treatment with antioxidants. The Fenton assay involved the reaction of hydroxyl radicals with dimethyl sulfoxide. Fenton reactivity was most marked with AA followed by GSH, and hydrogen peroxide also exhibited minor reactivity. Erionite generated an order of magnitude greater hydroxyl radicals than mordenite, normalized to the surface iron content, providing support for the hypothesis that the iron coordination at the mineral surface plays a significant role in bioactivity.

Topics: Aluminum Silicates; Asbestos; Hydrogen Peroxide; Hydroxyl Radical; Iron; Lung Neoplasms; Mesothelioma; Oxidation-Reduction; Pulmonary Fibrosis; Zeolites

The cytotoxicity of four tumorigenic minerals: erionite(w), erionite(c), UICC crocidolite, UICC chrysotile and nontumorigenic mordenite was compared in Chinese hamster lung V79 cells. The results indicate that the tumorigenic minerals were toxic by showing more than 50% toxicity for at least one dose between 10 and 100 micrograms/ml. Mordenite was nontoxic. Higher potency of erionite, however, was not evident in this system when the dose considered was expressed in mass units. On the other hand, when the degree of cytotoxicity was considered per number of mineral fibers, it was clear that fewer erionite fibers of all three dimensions (A greater than or equal to 3; L greater than or equal to 8.0 micrometers, W less than or equal to 0.25 micrometer; and L less than 5.0 micrometers, W less than or equal to 0.1 micrometer) than those of UICC crocidolite and UICC chrysotile were needed to produce similar toxicity. This suggests that the dose in number of fibers may be a better parameter than the total mass dose as a correlate of tumorigenic potential.

Topics: Aluminum Silicates; Animals; Asbestos; Asbestos, Crocidolite; Asbestos, Serpentine; Carcinogens; Cells, Cultured; Cricetinae; Lung Neoplasms; Zeolites