WTAP modulates macrophage polarization in rheumatoid arthritis by targeting exosomal circ-CBLB via m 6 A modification

Davwei YAN¹Lei Wan^1,2,3*

• ¹First Affiliated Hospital of Anhui University of Traditional Chinese Medicine, Hefei, China
• ²Center for Xin'an Medicine and Modernization of Traditional Chinese Medicine, Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, Anhui Province, China
• ³Key Laboratory of Xin'an Medicine, Ministry of Education, Anhui University of Chinese Medicine, Hefei, Anhui Province, China

Interactions between fibroblast-like synoviocytes (FLSs) and macrophages are pivotal in the pathogenesis of rheumatoid arthritis (RA). Exosomal circular RNAs (circRNAs) are key players in the communication between RA-FLSs and macrophages. In this study, we stimulated RA-FLSs with TNF-α to mimic the enhanced inflammatory microenvironment in RA and observed that circ-CBLB expression was significantly downregulated in response to the stimulation.Further functional validation showed that inhibition of exosome secretion intensified macrophage polarization toward the pro-inflammatory M1 phenotype. Screening of m6A modification-related enzymes combined with RNA pull-down and RIP-qPCR assays exhibited that WTAP protein directly bound to circ-CBLB and accelerated circ-CBLB degradation by enhancing its m6A modification levels. Functional experiments demonstrated that WTAP overexpression decreased exosomal circ-CBLB levels and promoted macrophage polarization toward the pro-inflammatory M1 phenotype, which was reversed by m6A modification site mutation. Conclusively, this study reveals a novel mechanism that exosomal circ-CBLB secreted from RA-FLSs affects macrophage polarization under the regulation of WTAP-mediated m6A modification, underscoring the potential of interventions targeting the WTAP-circ-CBLB axis in RA treatment.