Histone Deacetylase/Acetylase Activity in Total Synovial Tissue Derived From Rheumatoid Arthritis and Osteoarthritis Patients

inflammatory disorder of unknown origin. Histone deacetylase (HDA) activity is considered to play a major role in the transcriptional regulation of proinflamma-tory genes. We undertook this study to investigate the balance of histone acetylase and HDA activity in syno-vial tissue from RA patients compared with that from patients with osteoarthritis (OA) and normal controls. Methods. Activity of histone acetylases and HDAs was measured in nuclear extracts of total synovial tissue samples, which were obtained from RA and OA patients undergoing surgical joint replacement, and compared with the activity in synovial tissues from patients with-out arthritis. Tissue expression of HDAs 1 and 2 was quantified by Western blotting. In addition, immunohis-tochemistry was performed for HDA-2