Proteomic identification of macrophage migration-inhibitory factor upon exposure to TiO2 particles

Abstract

Inhalation of particulate matter aggravates respiratory symptoms in patients with chronic airway diseases, but the mechanisms underlying this response remain poorly understood. We used a proteornics approach to examine this phenomenon. Treatment of epithelial cells with BSA-coated titanium dioxide (TiO2) particles altered 20 protein spots on the two-dimensional gel, and these were then analyzed by nano-LC-MS/ MS. These proteins included defense-related, cell-activating, and cytoskeletal proteins implicated in the response to oxidative stress. The proteins were classified into four groups according to the time course of their expression patterns. For validation, RT-PCR was performed on extracts of in vitro TiO2-treated cells, and lung issues from TiO2-treated rats were analyzed by immunohistochemical staining and enzyme immunoassay. TiO2 treatment was found to increase the amount of mRNA for macrophage migration-inhibitory factor (MIF). MIF was expressed primarily in epithelium and was elevated in lung tissues and bronchoalveolar lavage fluids of TiO2-treated rats as compared with sham-treated rats. Carbon black and diesel exhaust particles also induced expression of MIF protein in the epithelial cells. © 2007 by The American Society for Biochemistry and Molecular Biology, Inc.