HIF-1α/IL-33 self-amplification circuit exacerbates the inflammation in RA.

<p>Rheumatoid arthritis synovial fibroblast (RASF) hyperplasia leads to tissue hypoxia, which induces upregulated expression of HIF-1α. This upregulated HIF-1α expression provokes IL-33 production by RASF, one of the main sources of IL-33. IL-33 in turn enhances HIF-1α expression in RASF, thus forming a self-amplification circuit that would perpetuate the inflammatory process in RA.