Role of Fn-14 receptor in TNF-induced inflammation and tissue destruction

About This Grant

PROJECT SUMMARY Tumor necrosis factor (TNF)-α is a major inflammatory cytokine involved in the pathogenesis of several autoimmune and inflammatory diseases, including rheumatoid arthritis (RA). Current approaches aim to curb TNF-α-induced inflammation and tissue damage by treating patients with TNF-α inhibitors (specific antibodies or soluble receptors). The ineffectiveness of TNF inhibitors in >40% of patients partly indicates that we do not yet fully understand the underlying signaling mechanisms to effectively target TNF-α. While the use of TNF inhibitors has provided new insights into human immune and inflammatory systems and the mechanisms involved in disease processes, adverse events, and the re-emergence of the disease upon cessation of therapy suggest that other pathways might be involved in re-establishing the disease. Previous studies from our lab using RA synovial fibroblasts (RASFs) and preclinical models of RA not only shed light on the mechanisms by which TNF- α utilizes cell surface or cellular proteins to cause progressive inflammation and tissue destruction but also provided novel pharmacological approaches to suppress TNF-α’s function in RA. In this proposal, our novel preliminary data show that TNF-α utilizes Fn-14 (fibroblast growth factor-inducible 14), a receptor originally characterized for mediating TWEAK cytokine signaling. Knockdown of Fn-14 significantly reduced TNF-α- induced RANTES, MCP-1 and MMP-1 production, and cellular expression of podoplanin and cadherin-11 in human RASFs. In Fn-14-overexpressing cells, even low TNF-α concentrations synergistically induced inflammation, suggesting a potential undescribed mechanism exploited by TNF-α to propagate inflammation. RNA-sequencing analysis revealed >200 differentially expressed genes (DEG) affected by Fn-14 knockdown in TNF-α stimulated RASFs. Gene set enrichment analysis (GSEA) on the RNA-seq data revealed that IFN-α and IFN-γ pathway responses were significantly altered. Intraperitoneal administration of Fn14 antagonist (L524- 0366; 10 mg/kg; daily from the disease onset) inhibited collagen antibody-induced arthritis in DBA1/J mice. Based on these novel observations, we hypothesize that TNF-α utilizes the Fn-14 receptor as a non-canonical signaling pathway to induce inflammation. Therefore, in specific aim 1, we plan to determine the molecular mechanisms through which TNF-α utilizes Fn-14 in the synthesis of inflammatory and tissue-destructive mediators in human RASFs and other cells relevant to TNF-α-driven diseases such as IBD and psoriasis. In specific aim 2, we plan to decipher the role of Fn-14 in TNF-α induced function and phenotypic changes in RASFs by using complex multicellular ex-vivo systems, including synovium-on-a-chip model and RA synovial tissue explants. Finally, in specific aim 3, we plan to validate the in vivo efficacy and inhibitory potential of Fn-14- targeted approaches in acute and chronic models of TNF-α-inflammation. The success of these studies will elucidate the role of Fn-14 as a non-canonical signaling receptor of the TNF-α signaling pathway and validate Fn-14 blockade as a potential therapeutic approach for the treatment of RA.