TNF and rheumatoid arthritis: Inflammatory mediators such as prostaglandins (PGs), leukotrienes (LTs) and tumor necrosis factor-alpha (TNF-α) are implicated in a wide variety of diseases such as rheumatoid arthritis (RA), osteoarthritis (OA), asthma, atherosclerosis, different types of cancers and diseases of the central nervous system [13,14,15,16,17,18,19,20,21,22].