Interstitial pulmonary fibrosis (IPF) has numerous etiologies and afflicts millions of individuals worldwide. Yet, there are no effective preventive agents or therapeutic approaches. This situation is due in large part to a lack of understanding of the fundamental molecular mechanisms that mediate the fibrogenic process. In the work proposed here, we have focused on two peptide factors that have been implicated by numerous researchers as central to the development of IPF. These factors are tumor necrosis factor alpha (TNF-a) and transforming growth factor beta one (TGF-B1). Our previous work and preliminary data show that TNF-a up-regulates the expression of TGF-B1 both in vitro and in vivo, but the basic mechanisms through which TNF-a influences TGF-B1 expression remain undefined. TNF-a has been considered by many to be a "master cytokine" that controls the expression of a number of biologically relevant molecules. In as much as TGF-B1 is considered to be a primary "fibrogenic factor", we have set forth the central hypothesis that TNF-a induces TGF-B1 production by transcriptional regulation through the MEK/ERK pathway in lung cells: and the pathway of fibrogenesis mediated by TNF-a through TGF-B1 can be interrupted by specific siRNAs that mediate the degradation of transcripts that code for TNF-a, MP-1- a key component of MEK/ERK phosphorylation, and TGF-B1. Specific Aim 1 will establish MEK/ERK transduction pathways from TNF-a to TGF-B1 and the transcriptional mechanisms of expression. Aim 2 will focus on other factors that could up-regulate TGF-B1 through this same pathway; and in Aim 3, we will learn if the epithelial and mesenchymal cells in vivo in the lung exhibit the same transduction and transcriptional pathways in health and disease. These studies will provide specific targets for potential therapeutic approaches through the use of small interfering RNAs (siRNA). Thus, in Aim 4, we will show that an siRNA we have designed blocks endogenous TNF-a gene expression. We propose to use this construct as well as an siRNA that degrades MP1 (a key protein in MEK/ERK phosphorylation), and finally an siRNA that will block TGF-B1 expression, and ultimately the development of IPF in our established animal models.