To the Editor:
High mobility group box 1 (HMGB1) chromosomal protein, an endogenous molecule with multiple intra- and extracellular effects, is also defined as a novel proinflammatory cytokine, proved to contribute to the pathogenesis of several rheumatic diseases1. Evidence grows showing that HMGB1 plays a role as an important endogenous mediator of arthritis. Significantly elevated levels of HMGB1 are reported in the sera and synovial fluid of patients with rheumatoid arthritis (RA) as compared to patients with osteoarthritis2. Levels of HMGB1 are increased in the synovial tissues of animals and humans with joint inflammation3. HMGB1 mediates the development of arthritis when applied into the joints of naive mice4 and treatment strategies directed against HMGB1 attenuate progression in collagen-induced arthritis1. In RA, characterized by chronic autoimmune destructive joint inflammation, extensive production of proinflammatory cytokines is known to mediate tissue damage.
HMGB1, either released actively from myeloid and dendritic cells or passively during local cell death in the joint, could sustain chronic synovitis by several mechanisms including an augmentation of production of several proinflammatory mediators such as interleukin 1 (IL-1), tumor necrosis factor-α (TNF-α), and IL-6, all known to be important in the pathogenesis of arthritis5.
In a cross-sectional study, we investigated the relationship between concentrations of HMGB1 and proinflammatory cytokines and disease characteristics in a cohort6 of 81 postmenopausal patients with RA. The …
Address correspondence to Dr. R. Pullerits, The Sahlgrenska Academy, University of Gothenburg, Department of Rheumatology and Inflammation Research, Guldhedsgatan 10A, 41346, Gothenburg, Sweden. E-mail: rille.pullerits{at}rheuma.gu.se