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OXIDANTT GENERATION PROMOTES IRON SEQUESTRATION IN BEAS-2B CELLS EXPOSED TO ASBESTOS
Citation:
Stonehuerner, J., X. Wang, Y. Wu, L. A. Dailey, J. Richards, I. Jaspers, C. Pintadosi, AND A J. Ghio. OXIDANTT GENERATION PROMOTES IRON SEQUESTRATION IN BEAS-2B CELLS EXPOSED TO ASBESTOS. Presented at American Thoracic Society Annual Conference, San Diego, CA, March 20 - 25, 2005.
Description:
Lung injury following asbestos exposure is associated with an oxidative stress that is catalyzed by iron in the matrix, complexed to the surface, or both. We hypothesized that the cellular response to asbestos includes the transport and sequestration of iron by 1) generation of superoxide for ferrireduction, 2) upregulation of divalent metal transporter-1 (DMT1) for intracellular transport of Fe2+, and 3) increased production of cellular ferritin. BEAS-2B cells with normal and elevated Cu, Zn superoxide (SOD) expression were generated after infection with Ad5CMV3 and AdSOD1 respectively. Using dichlorodihydrofluorescein fluorescence and fluorescence microscopy, we demonstrated a significantly increased generation of superoxide after exposure of BEAS-2B cells to asbestos. Employing Western blot analysis and RT-PCR, fiber exposure was also shown to increase DMT1 protein and mRNA expression in the BEAS-2B cells. Following correction to GAPDH, mRNA for DMT1 was 12.5 ? 2.8 and 28.7 ? 3.4 after control and asbestos incubations respectively. Incubation with asbestos elevated cellular iron (measured by inductively coupled plasma optical emission spectroscopy) and ferritin concentrations (measured by enzyme immunoassay), and these responses were diminished in cells with an enhanced expression of SOD. Finally, fiber exposure increased supernatant concentrations of IL-8 (13.7 fold change) quantified by ELISA but this inflammatory mediator was increased more in cells with elevated SOD expression (18.1 fold change). We conclude that the response of respiratory epithelial cells to asbestos includes oxidant-mediated mechanisms to sequester catalytically active iron associated with the fiber. This abstract does not reflect USEPA policy.