Expression of PADI4 during rheumatoid arthritis development

Peptidyl deiminase 4 (PADI4) catalyzes peptidylarginine to citrulline. The gene encoding PADI4 is associated with rheumatoid arthritis (RA) in some populations. The levels of PADI4, anti-CCP, and RF were measured in the blood of patients suffering from RA and osteoarthritis (OA) for less than six months using ELISA. The levels were also measured in the blood of patients that have been diagnosed with RA for more than three years. As controls, samples from healthy subjects or patients with ankylosing spondylitis (AS), epidemic pleurodynia (EP), OA, psoriatic arthritis (PA), systemic lupus erythematosus (SLE), gouty arthritis (GA), or Still’s disease (ST) were also assayed. Of patients with early RA, 68.7% had significantly higher levels of PADI4 than patients with early OA. Patients with RA for a longer period of time had a higher expression of PADI4 than patients with SLE, ST, and GA, but they were similar to healthy subjects or patients with AS, EP, OA, or PA. The level of PADI4 was significantly correlated to the levels of RF and anti-CCP in blood samples of RA, but not in the samples of other diseases and those of healthy subjects. The level of PADI4 relates to the disease activity and clinical performance.