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Laboratory Investigation (2004) 84, 10131023
& 2004 USCAP, Inc All rights reserved 0023-6837/04 $30.00
www.laboratoryinvestigation.orgAsbestos-derived reactive oxygen species
activate TGF-b1Derek A Pociask1, Patricia J Sime2 and Arnold R Brody11Lung Biology Program, Department of Pathology, Tulane University Health Science Center, New Orleans, LA,
USA and2Department of Medicine, University of Rochester, Rochester, NY, USATransforming growth factor-beta1 (TGF-b1) is a potent peptide that inhibits epithelial and mesenchymal cell
proliferation and stimulates the synthesis of extracellular matrix components. This cytokine is produced in a
biologically latent complex bound to a latent-associated peptide (LAP), and it is the disassociation of this
complex that regulates TGF-b activity. A number of mechanisms have been shown to activate TGF-b1. We show
here that reactive oxygen species (ROS), generated by the iron in chrysotile or crocidolite asbestos, mediate the
biological activity of TGF-b1. Recombinant human latent TGF-b1 was activated in a cell free system in the
presence of asbestos and ascorbic acid. Latent TGF-b1 was overexpressed in both A549 and mink lung
epithelial cell lines through an adenovirus vector containing the full-length construct for porcine TGF-b1. This
latent TGF-b1 was activated in a concentration-dependant fashion by introducing asbestos into the cell cultures.
This activation was reduced significantly through the use of superoxide dismutase, catalase or deferoxamine.
Amino-acid constituents of the LAP were oxidized as demonstrated by the appearance of carbonyls detected
by Western analysis. The oxidized LAP could no longer form a complex with TGF-b1. Our data support
the postulate that ROS derived from asbestos provide a mechanism for activating TGF-b1 in the alveolar
environment by oxidizing amino acids in LAP.Laboratory Investigation (2004) 84,10131023, advance online publication, 3 May 2004; doi:10.1038/labinvest.3700109Keywords: chrysotile asbestos; latent-associated peptide; transforming growth factor b1Asbestos fibers are known to cause lung scarring
(asbestosis) in man and animals and are cytotoxic in
vitro and in vivo.1 Part of this toxic effect of asbestos
has been attributed to reactive oxygen species
(ROS). These ROS are formed indirectly through
macrophage and inflammatory cell stimulation and
directly on the alveolar surfaces through Fenton
reactions catalyzed by the iron content of the
asbestos.1 ROS have been demonstrated to contribute to asbestos-induced alveolar cell injury and
carcinogenesis through generation of DNA strand
breaks,2 lipid peroxidation3 and apoptosis.1 These
cytotoxic and fibrogenic effects can be decreased
through...