The role of high mobility group box chromosomal protein 1 in rheumatoid arthritis.

High mobility group box chromosomal protein 1 (HMGB1) is a ubiquitous highly conserved single polypeptide in all mammal eukaryotic cells. HMGB1 exists mainly within the nucleus and acts as a DNA chaperone. When passively released from necrotic cells or actively secreted into the extracellular milieu in response to appropriate signal stimulation, HMGB1 binds to related cell signal transduction receptors, such as RAGE, TLR2, TLR4 and TLR9, and becomes a proinflammatory cytokine that participates in the development and progression of many diseases, such as arthritis, acute lung injury, graft rejection immune response, ischaemia reperfusion injury and autoimmune liver damage. Only a small amount of HMGB1 release occurs during apoptosis, which undergoes oxidative modification on Cys106 and delivers tolerogenic signals to suppress immune activity. This review focuses on the important role of HMGB1 in the pathogenesis of RA, mainly manifested as the aberrant expression of HMGB1 in the serum, SF and synovial tissues; overexpression of signal transduction receptors; abnormal regulation of osteoclastogenesis and bone remodelling leading to the destruction of cartilage and bones. Intervention with HMGB1 may ameliorate the pathogenic conditions and attenuate disease progression of RA. Therefore administration of an HMGB1 inhibitor may represent a promising clinical approach for the treatment of RA.