MMP9 and rheumatoid arthritis: For instance, gallic acid suppresses the levels of cytokines IL-1 and IL-6, chemokines MCP-1 and MCP-3, cyclooxygenase-2 (COX-2), and matrix metalloproteinase-9 (MMP-9) in fibroblast-like synoviocytes in rheumatoid arthritis [33].