Similar to NO, PGE2 is an inflammatory mediator generated at inflammatory sites by COX-2, which is involved in the pathogenesis of many chronic inflammatory diseases, such as rheumatoid arthritis, cancer, and cardiovascular disease (Lipsky, 1999[22]; Rocca and FitzGerald, 2002[32]). This evidence concerns the gene PTGS2 and rheumatoid arthritis.