CXCL8 and rheumatoid arthritis: However, simultaneous knockdown of NF-κB p65 and p38 MAP kinase almost completely abolished the ORM2-induced increase in the mRNA expression levels of IL6 and CXCL8 (Fig. 3i, j), suggesting that both the NF-κB p65 and p38 MAP kinase signaling pathways are required for ORM2-induced IL-6 and CXCL8 production by RA-FLSs.