Objective: Although serum amyloid A (SAA) has been used as a marker of inflammation, its role in leucocyte recruitment and angiogenesis has not been well established in RA. CCL20 is a chemokine involved in the migration of CCR6-expressing Th17 cells. To study the contribution of SAA to the recruitment of Th17 cells, we investigated the effects of SAA on CCL20 production by RA synoviotytes.
Methods: Synoviocytes isolated from RA patients were stimulated with recombinant SAA and cellular supernatants were analysed by CCL20-specific ELISA. CCL-20 mRNA expression was analysed by RT-PCR.
Results: SAA is a most potent inducer of CCL20 secretion in RA synoviocytes compared with other inflammatory cytokines (IL-1beta, TNF-alpha and IL-17A). SAA stimulation induced CCL20 mRNA expression in RA synoviocytes, which was not affected by polymyxin B pre-treatment. SAA-induced CCL20 production was down-regulated by NF-kappaB inhibition and partially by c-jun N-terminal kinase (JNK) inhibition. SAA-induced CCL20 production was also suppressed by dexamethasone or FK506.
Conclusion: These findings suggest that SAA may be implicated in the recruitment of lymphocytes, including CCR6-expressing Th17 cells, in RA synovium by up-regulating CCL20 production in synoviocytes.