The molecular mechanisms though which inhaled inorganic particles cause interstitial pulmonary fibrosis (IPF) are being investigated. Since there are numerous potential mediators that will be expressed during disease development, it is essential that studies focus on selected molecules that could be key. We have shown that tumor necrosis factor alpha receptor knock out (TNF-alphaRKO) mice are protected from the fibrogenic effects of inhaled asbestos fibers. These animals exhibit reduced expression of other cytokines such as platelet-derived growth factor, transforming growth factor alpha (TGF-alpha) and TGF-beta1, even though TNF-alpha expression remains up-regulated. Thus, we have focused this proposal on the hypothesis that TNF-alpha mediates the development of interstitial pulmonary fibrosis through regulation of TGF- beta production.
Four Specific Aims will directly test this postulate: 1) To demonstrate reduced TGF-beta expression in the lungs of asbestos- exposed TNF-alpha receptor knockout (TNF-alphaRKO) mice by in situ hybridization (ISH) and immunohistochemistry (IHC). Our preliminary data show that these mice lack expression of TGF-beta1 after asbestos exposure. If this proves to be true in the final analysis, an important step in testing the postulate will be accomplished. 2) a. To establish whether or not latent or active TGF-beta transduced by adenovirus vector into the lungs of the TNF-alphaRKO mice induces fibroproliferative lung disease in the fibrogenic-resistant mice. b. To expose the virally-transduced animals to asbestos and establish TGF-beta expression as a mediator of fibrogenesis. If TGF-beta1 transduced by an adenovirus vector restores susceptibility to developing fibrogenesis, further evidence of a central role of this growth factor will be in hand. 3) To maintain, in culture, alveolar epithelial and mesenchymal cells from TNF-alphaRKO and TGF-betaKO mice to determine if TNF-alpha receptor signaling is necessary to up-regulate TGF-beta and collagen gene expression in vitro after asbestos exposure. The influence of TNF-alpha on expression of TGF-beta1 and pro alpha1(I) collagen (as postulated) is completely unknown in primary pulmonary cells fro normal and knockout through treatment of mesenchymal cells with antisense vectors directed at expression of the TNF-alpha and TGF-beta genes, As a potential therapeutic approach, we show that an anti-sense TGF-beta1 gene vector blocks expression of TGF-beta1 as well as pro alpha1(I) collagen after treatment with TNF-alpha.
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