TNF and rheumatoid arthritis: Curcumin has an ability to downregulate the expression of the IκBα gene, cyclooxygenase-2 gene (COX-2), prostaglandin E-2 (PGE-2), interleukin-1–6–8 (IL-1, IL-6, IL-8), and tumor necrosis factor-α (TNF-α) in synovial fibroblasts obtained from patients with rheumatoid arthritis.