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A7168 - TNF-Related Weak Inducer of Apoptosis (TWEAK) Is a Predicted Mediator of Fibroblast Activation in Response to Eosinophil-Degranulation and Promotes Myofibroblast Differentiation
Author Block: N. K. Sandbo1, S. Esnault1, A. Tubbs1, J. Aoki1, Y. A. Bochkov2, N. N. Jarjour1, J. Leet1, K. Bernau1; 1Medicine, University of Wisconsin-Madison, Madison, WI, United States, 2Pediatrics, University of Wisconsin-Madison, Madison, WI, United States.
Background: Chronic asthma is characterized by non-reversible airflow obstruction that results, in part, from airway remodeling and extracellular matrix deposition that is driven by activity of resident lung fibroblasts. In asthma, eosinophils (EOS) contribute to airway inflammation and remodeling via the release of toxic granule proteins and other mediators, including cytokines, which may lead to fibroblast activation and differentiation to a pro-fibrotic myofibroblast phenotype. We have recently shown that eosinophil activation with IL-3 led to a robust eosinophil degranulation on immunoglobin-G (IgG)-coated plates. In human lung fibroblasts (HLF) exposed to conditioned media obtained from IL-3-activated eosinophils followed by degranulation on IgG, whole transcriptome RNA-sequencing followed by Ingenuity Pathway Analysis identified upregulation of pathways involved in inflammation, tissue remodeling and lipid synthesis. One of the identified upstream regulators was Tumor Necrosis Factor Soluble Family Member 12 (TNSF12), which is also known as TNF-related weak inducer of apoptosis (TWEAK). In the present study, we analyze the effects of TWEAK on primary HLF signaling and gene expression. Methods: Expression and regulation of TWEAK and its receptor, FN14 were determined in human lung fibroblasts (HLF). HLF were treated with varying dose of human recombinant TWEAK for the indicated timepoints. Differentially expressed genes cell lysates from TWEAK-activated HLF were analyzed by realtime quantitative PCR, PAGE and western blotting. Results: TWEAK and its cognate receptor, FN14 are highly expressed in HLF. Treatment of HLF with TWEAK results in increased smooth muscle α- actin and the extra type III domain-containing fibronectin (EDA-FN) transcription and protein levels, indicating differentiation to a myofibroblast state. TWEAK also strongly increases the gene expression of its receptor, FN14, and IL-6 and IL-8, supporting a potential role in mediating inflammation. Conclusions: In summary, TWEAK and its receptor, FN14, is highly expressed in HLF. Exposure of HLF to TWEAK in vitro results in myofibroblast differentiation. We posit that TWEAK may promote myofibroblast differentiation and ECM expression in response to exposure to EOS-derived degranulation products. Thus, TWEAK may be an important mediator of airway remodeling in asthma.