Session Title: Cytokines, Mediators, and Gene Regulation
Session Type: Abstract Submissions (ACR)
Recently, we have shown that Th17, but not Th1 cells, from patients with early rheumatoid arthritis (RA) are potent activators of RA synovial fibroblasts (RASF) resulting in autocrine IL-17A production. This IL-17A production results in a pro-inflammatory loop, which is characterized by an up-regulation in pro-inflammatory cytokines and cartilage degrading enzymes. The autocrine IL-17A production by Th17 cells is critical for the perseverance of the pro-inflammatory loop, but the mechanism underlying the autocrine IL-17A induction is unclear. The objective of this study is to investigate the mechanism responsible for the autocrine IL-17A induction upon Th17-RASF interaction.
CD4+CD45RO+CCR6+ (Th17) and CD4+CD45RO+CCR6- (Th1) cells were isolated by fluorescence-activated cell sorting (FACS) sorting from healthy controls and early RA patients. These cells were co-cultured with RASF, in the presence of neutralizing antibodies directed against soluble IL-6R (anti-sIL-6R) and/or IL-1β, and celecoxib. Gene expression profiles were generated and supernatant was collected for cytokine analyses by enzyme-linked immunosorbent assay (ELISA).
Gene expression analyses revealed that the genes encoding for IL-6 and IL-1β were up-regulated in Th17-RASF cultures. These data were confirmed by ELISA and quantitative polymerase chain reaction (Q-PCR), respectively. Since IL-1β and IL-6 may be involved in IL-17/Th17 polarization we examined the contribution of these cytokines on the autocrine IL-17A loop. Blockade of IL-1β and IL-6 significantly suppressed IL-17 production. However the effects of IL-1β and IL-6 blockade were limited, indicating the requirement of an additional mechanism.
Interestingly, the genes encoding for cyclo-oxygenase-2 (COX-2) and prostaglandin-E-synthase (PTGES), which are involved in prostaglandin-E2 (PGE2) synthesis, were also up-regulated in Th17-RASF cultures. This was associated with a dramatic increase of PGE2 production in Th17-RASF cultures compared to Th1-RASF cultures. Treatment of Th17-RASF cultures with celecoxib, a COX-2 inhibiter, resulted in significant and specific inhibition of the fraction of IL-17A producing cells and the IL-17A levels. No inhibitory effects were found on IFN-γ and TNF-α production. Moreover, celecoxib treatment functionally inhibited the pro-inflammatory loop as production of the pro-inflammatory mediators IL-6 and IL-8 and tissue destructive enzymes MMP-1 and MMP-3 were significantly suppressed.
These findings show the critical role of the COX/PGE2 pathway in the autocrine IL-17A production upon Th17 and synovial fibroblast interaction. Inhibition of this pathway down-regulates the pro-inflammatory feedback loop induced by Th17-RASF interaction leading to less production of pro-inflammatory cytokines and destructive mediators.
S. M. J. Paulissen,
J. P. van Hamburg,
P. S. Asmawidjaja,
J. M. W. Hazes,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-cyclooxygenaseprostaglandin-e2-pathway-is-critical-for-autocrine-il-17a-production-by-th17-cells-upon-synovial-fibroblast-interaction/