Novel anti-inflammatory actions of nobiletin, a citrus polymethoxy flavonoid, on human synovial fibroblasts and mouse macrophages

We previously reported that nobiletin (5,6,7,8,3',4'-hexamethoxy flavone), a citrus polymethoxy flavonoid, effectively interferes with the production of promatrix metalloproteinase (proMMP)-9/progelatinase B in rabbit synovial fibroblasts [J. Rheumatol. 27 (2000) 20]. In this paper, we further examine the effects of nobiletin on the production of cyclooxygenases (COXs), prostaglandin (PG) E-2, and proinflammatory cytokines in human synovial fibroblasts and the mouse macrophage J774A.1 cell line. Nobiletin suppressed the interleukin (IL)-1-induced production of PGE(2) in human synovial cells in a dose-dependent manner (<64 muM). Additionally, it selectively downregulated COX-2, but not COX-1 mRNA expression. Nobiletin also interfered with the lipopolysaccharide-induced production of PGE(2) and the gene expression of proinflammatory cytokines including IL-1alpha, IL-1beta, TNF-alpha and IL-6 in mouse J774A.1 macrophages. In addition, nobiletin downregulated the IL-1-induced gene expression and production of proMMP-1/procollagenase-1 and proMMP-3/prostromelysin-1 in human synovial fibroblasts. In contrast, production of the endogenous MMP inhibitor, TIMP-1, was augmented by nobiletin. These anti-inflammatory actions of nobiletin are very similar to those of anti-inflammatory steroids such as dexamethasone, and the upregulation of TIMP-1 production is a unique action of nobiletin. Therefore, these results further support the notion that nobiletin is likely to be a candidate for characterization as a novel immunomodulatory and anti-inflammatory drug. (C) 2003 Elsevier Science Inc. All rights reserved.