Effects of (-)-epigallocatechin-3-gallate on cyclooxygenase 2, PGE ₂, and IL-8 expression induced by IL-1β in human synovial fibroblasts

The objective of this study was to examine the effects of (-)-epigallocatechin-3-gallate (EGCG) on cyclooxygenase 2 (COX-2), prostaglandin E₂ (PGE₂), and interleukin 8 (IL-8) expression induced by IL-1β in human synovial fibroblasts. Cells were enzymatically isolated from synovial tissue taken from patients undergoing joint replacement surgery for osteoarthritis. Reverse transcriptase-polymerase chain reaction, immunocytochemistry, and western blotting were used to assess the COX-2 gene and protein expression with the associated mechanisms. PGE₂ and IL-8 secretion into the culture medium was assayed by enzyme-linked immunosorbent assay. COX-2 upregulation in synovial fibroblasts induced by IL-1β was significantly suppressed by EGCG in a dose-dependent manner. PGE₂ and IL-8 secretion was also induced by IL-1β stimulation and significantly suppressed by EGCG. The mechanism was associated with the phosphorylation of IKKβ. EGCG may inhibit the expression of inflammatory mediators, such as COX-2, PGE₂, and IL-8, induced by IL-1β in human synovial fibroblasts. EGCG may be of value in the treatment of synovial inflammation.