title: Asbestos inhalation induces tyrosine nitration associated with extracellular signal-regulated kinase 1/2 activation in the rat lung.
abstract: Nitration of proteins by peroxynitrite (ONOO-) has been shown to critically alter protein function in vitro. We have shown previously that asbestos inhalation induced nitrotyrosine formation, a marker of ONOO- production, in the rat lung. To determine whether asbestos-induced protein nitration may affect mitogen-activated protein kinase (MAPK) signaling pathways, lung lysates from crocidolite and chrysotile asbestos-exposed rats and from sham-exposed rats were immunoprecipitated with anti-nitrotyrosine antibody, and captured proteins were subjected to Western blotting with anti-phospho-extracellular signal-regulated kinase (ERK)1/2 antibodies. Both types of asbestos inhalation induced significantly greater phosphorylation of ERK1/2 in rat lung lysates than was noted after sham exposure. Phosphorylated ERK proteins co-immunoprecipitated with nitrotyrosine. Moreover, in MAPK functional assays using Elk-1 substrate, immunoprecipitated phospho-ERK1/2 in lung lysates from both crocidolite-exposed and chrysotile-exposed rats demonstrated significantly greater phosphorylation of Elk-1 than was noted after sham exposure. Asbestos inhalation also induced ERK phosphorylation in bronchoalveolar lavage cells. Lung sections from rats exposed to crocidolite or chrysotile (but not from sham-exposed rats nor from rats exposed to "inert" carbonyl iron particles) demonstrated strong immunoreactivity for nitrotyrosine and phospho-ERK1/2 in alveolar macrophages and bronchiolar epithelium. These findings suggest that asbestos fibers may activate the ERK signaling pathway by generating ONOO- or other nitrating species that induce tyrosine nitration and phosphorylation of critical signaling molecules.
authors.affiliation: Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799, USA.
authors.forename: Akitaka
authors.initials: A
authors.lastname: Iwagaki
authors.forename: Nonghoon
authors.initials: N
authors.lastname: Choe
authors.forename: Yingyue
authors.initials: Y
authors.lastname: Li
authors.forename: David R
authors.initials: DR
authors.lastname: Hemenway
authors.forename: Elliott
authors.initials: E
authors.lastname: Kagan
mesh_terms: D000818:Animals; D017638:Asbestos, Crocidolite / Q000008:administration & dosage / Q000494:pharmacology*; D017632:Asbestos, Serpentine / Q000008:administration & dosage / Q000494:pharmacology*; D004789:Enzyme Activation; D007150:Immunohistochemistry; D019570:Inhalation Exposure; D008168:Lung / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D051381:Rats; D011916:Rats, Inbred F344; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D017632:Asbestos, Serpentine; D009566:Nitrates; D017638:Asbestos, Crocidolite; D014443:Tyrosine; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases