TRPA1 as regulator of fibroblast activation in rheumatoid arthritis

• Applicant: Dr. Torsten Lowin
• Subject Area: Rheumatology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 548054407

Rheumatoid arthritis (RA) is an inflammatory joint disease that affects around 1% of the adult population. Reactive oxygen species (ROS) contribute to RA, as they generate endoplasmic reticulum stress, enhance pro-inflammatory cytokines, and foster autoimmunity. TNF is a key mediator of RA joint pathology and upregulates TRPA1, a calcium-sensitive ion channel that mediates pain perception and environmental irritant sensing. TRPA1 activates calcium-sensitive signaling pathways, including autophagy and apoptosis. TRPA1 is regulated by Nrf2, which limits TNF's pro-inflammatory effects. TRPA1 expression is elevated in TNF-stimulated FLS and activation of TRPA1 using cannabinoids, such as tetrahydrocannabinol (THC) or cannabigerol (CBG), induces cell death, indicating that TRPA1 is a potential target for treating RA. We devised five aims to pinpoint the role of TRPA1 in RA. The first objective is to locate TRPA1 within FLS and identify which immune cell populations and FLS subpopulations express this protein in synovial tissue. The second objective is to examine how Nrf2 regulates TRPA1 and its signaling in FLS. The third objective is to investigate the downstream effects that occur after TRPA1 activation and determine which mediators are involved. The fourth objective is to determine the effects of TRPA1 ligation in vivo using two different mouse models of experimental arthritis. The final objective is to validate the functional findings obtained from the second, third, and fourth objectives in an ex vivo trial using precision-cut tissue slices of human synovial tissue. In order to approach these research questions adequately, we will employ state-of-art techniques such as imaging mass cytometry (IMC), RNA sequencing, Precision-cut tissue slices, micro-mass organoid cultures, CRISPR-generated knockouts, immunofluorescence, flow cytometry and siRNA knockdown. In addition, the hTNFtg and the collagen-induced arthritis mouse model will be employed. The experiments aim to determine the cellular localization of TRPA1 protein in RA-FLS and immune cells in synovial tissue and identify downstream signaling pathways and expression patterns of TRPA1 protein in different cell types in RA tissue sections. The involvement of Nrf2 in up-regulating TRPA1 and its downstream effects will be investigated, as well as whether TRPA1 regulates the ability of FLS to form lining layer structures like those found in vivo. TRPA1-regulated pathways and downstream kinases will be identified, revealing potential therapeutic targets. In vivo effects of TRPA1 agonism and antagonism will be studied in mouse arthritis models, and findings will be verified in human synovial tissue and FLS organoids. Finally, the impact of TRPA1 on cell death and calcium mobilization will be confirmed under ex vivo conditions.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Jörg Hans Wilhelm Distler