Published ahead of print on November 4, 2005, doi:10.1165/rcmb.2004-0275OC Am. J. Respir. Cell Mol. Biol., Volume 34, Number 3, March 2006, 286-292 A more recent version of this article appeared on March 1, 2006
Submitted on August 26, 2004 Oxidant Generation Promotes Iron Sequestration in BEAS-2B Cells Exposed to AsbestosXinchao Wang1,1 Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina, Chapil Hill, NC, USA; School of Public Health, Zhengzhou University, Zhengzhou, Henan, China, 2 School of Public Health, Zhengzhou University, Zhengzhou, Henan, China, 3 National Health and Environmental Effects Research Laboratory, United States Environmental Protection Agency, Chapel Hill, NC, USA, 4 Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina, Chapil Hill, NC, USA, 5 Department of Medicine, Duke University Medical Center, Durham, NC, USA * To whom correspondence should be addressed. E-mail: ghio.andy{at}epa.gov.
Lung injury following asbestos exposure is associated with an oxidative stress that is catalyzed by iron in the fiber matrix, complexed to the surface, or both. We tested the hypothesis that the cellular response to asbestos includes the transport and sequestration of this iron through 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 where the metal is stored in a catalytically less reactive state. BEAS-2B cells with normal and elevated Cu, Zn superoxide (SOD) expression were employed for in vitro investigations. After exposure of these cells to asbestos, we demonstrated by fluorescence methodology a significantly increased generation of superoxide with ferrireductive capacity. Fiber exposure also increased DMT1 protein and mRNA expression in the BEAS-2B cells. Incubation with asbestos elevated cellular iron and ferritin concentrations, and these responses were diminished in cells with an enhanced expression of SOD. Finally, fiber exposure increased supernatant concentrations of IL-8 but this inflammatory mediator was actually increased in cells with elevated SOD expression. We conclude that the response of respiratory epithelial cells to asbestos includes oxidant-mediated mechanisms to sequester catalytically active iron associated with the fiber.
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||