Upregulation of Fatty Acid Metabolism in Activated Synovial CD4 T Cell Populations in Rheumatoid Arthritis 2259803

Abstract Introduction Rheumatoid arthritis (RA) is an autoimmune disease involving joint damage driven by infiltrating immune populations. The RA synovium accumulates T peripheral helper cells (Tph), a T cell population that expresses high levels of PD-1, ICOS, and CXCL13 and lacks CXCR5. Circulating T cells from RA patients show a range of metabolic abnormalities. However, the metabolic features of synovial Tph cells and how these features regulate function remain unclear. Methods We utilized SCENITH to interrogate bioenergetic profiles of T cells from seropositive RA synovial fluid. Single cell RNA-seq data of T cells from RA synovial tissue was analyzed to identify metabolic genes upregulated in synovial Tph cells. We confirmed protein expression of an identified target, FATP2, in RA synovial fluid T cells. BODIPY 493/503 and BODIPY FL-C16 were used to assess neutral lipid content and fatty acid uptake capacity in RA synovial fluid T cells. BODIPY FL-C16 was used to assess the impact of FATP2 on fatty acid uptake capacity in CRISPR-modified human memory CD4 T cells. Results SCENITH revealed that Tph cells showed the highest baseline puromycin binding, reflecting high metabolic activity, and reduced oligomycin sensitivity among RA synovial fluid T cells. Single cell RNA-seq and flow cytometric analysis identified the selective upregulation of FATP2 within RA synovial Tph cells. Consistent with this, RA synovial fluid Tph cells have heightened neutral lipid content and fatty acid uptake capacity. CRISPR deletion of FATP2 in human memory CD4 T cells led to decreased fatty acid uptake. Conclusion Tph cells show heightened global metabolic activity compared to other T cells in RA synovial fluid. Synovial fluid Tph cells display increased lipid accumulation, fatty acid uptake capacity, and selective upregulation of FATP2 suggesting an altered lipid metabolism. FATP2 serves a non-redundant role in exogenous fatty acid uptake in human CD4 T cells. Funding Source This work is funded in part by a Burroughs Wellcome Fund Career Award in Medical Science and R01 AR078769 from NIAMS (to DAR). RTB is supported by T32 AR007530 from NIAMS. Topic Categories Basic Autoimmunity (BA)