CCL2 and rheumatoid arthritis: Nesfatin-1 induces c-c motif chemokine ligand 2 (CCL2) overexpression through the MEK/ERK pathway in RA synovial fibroblast, in which overexpressed CCL2 enhanced the polarization of M1 macrophages by treating THP-1-derived (M0) macrophages with synovial fibroblast conditioned medium (41).