Like NF-κB p65 siRNA, p38 siRNA also strongly inhibited the ORM2-induced increase in IL6 and CXCL8 mRNA levels (Fig. 3g, h), demonstrating that p38 MAP kinase is another major signaling molecule that mediates the promotive effect of ORM2 on IL-6 and CXCL8 expression levels in RA-FLSs. This evidence concerns the gene CXCL8 and rheumatoid arthritis.