TNF and rheumatoid arthritis: It had shown that TNF-α was increased in the synovium and cartilage of RA patients, which could promote the cartilage destruction by inhibiting the collagen synthesis, stimulating the fibroblasts and chondrocytes to produce the prostaglandins and collagenase, stimulating the chondrocytes to secrete metalloproteinases, inducing the differentiation of peripheral blood mononuclear cells into osteoclasts, etc. [39].