PPBP and rheumatoid arthritis: It can also reduce the phosphorylation of I-κB and NF-κB in RA-FLS (Wang et al., 2021), which in turn suggests that PEVs may activate the I-κB and NF-κB signaling pathway by binding CXCL7 to CXCR2, thus promoting migration and invasion of RA-FLS (Zhang et al., 2018; Wang et al., 2021).