454 The Role of bHLHe40 in Systemic Sclerosis-associated Pulmonary Fibrosis

Abstract

OBJECTIVES/GOALS: The dominant complication of Systemic Sclerosis (SSc) is clinically severe and commonly fatal pulmonary fibrosis (PF). We sought to determine the downstream regulatory role of the basic Helix-Loop-Helix protein 40 (bHLHe40), in response to Insulin-like Growth Factor II (IGF-II) on Pro-Lysyl Oxidase cleavage products. METHODS/STUDY POPULATION: We examined the response of primary pulmonary fibroblasts cultured from the lungs of control donors and SSc lung explants to IGF-II as well as human recombinant Lysyl Oxidase Propeptide (LOX-PP). In addition, we utilized an experimentally-induced model of lung fibrosis with intratracheal bleomycin administration. We used qPCR and immunoblotting to quantify mRNA and protein levels, respectively. We used sequence-specific small-interfering RNA to silence targeted genes. Immunoblots were quantified in ImageJ (NIH) and statistical analyses were performed in GraphPad Prism. RESULTS/ANTICIPATED RESULTS: IGF-II regulates levels of Pro-LOX, active LOX, and LOX-PP, as well as isoforms of proteases Bone Morphogenetic Protein 1 (BMP1) and Tolloid-like 1 (TLL1). The transcription factorbHLHe40 localizes to the nucleus in response to IGF-II. bHLHe40 silencing downregulated TLL1, abrogating the enzymatic cleavage of Pro-LOX. SSc lungs have higher baseline levels of the total (N-glycosylated/unglycosylated) LOX-PP than normal lung tissues, and baseline levels of LOX-PP correlated with TLL1 Isoform 2 in SSc lungs. LOX-PP contributes to the development and progression of SSc-PF by mediating changes consistent with the extracellular matrix deregulation implicated in SSc-PF: elevated levels of Collagen 3A1 (COL3A1), Fibronectin-1 (FN1), and Plasminogen Activator Inhibitor-1 (PAI1). DISCUSSION/SIGNIFICANCE: Our findings indicate that bHLHe40, TLL1, and LOX-PP may serve as targets of therapeutic intervention to stop the progression of SSc-PF. Since activation of common fibrotic pathways are involved in different diseases characterized by lung fibrosis such as IPF, our findings may have wider implications for lung fibrosis associated with other diseases.