Lower expression of histamine H₄ receptor in synovial tissues from patients with rheumatoid arthritis compared to those with osteoarthritis

The aim of this study is to compare the expression level of histamine H₄ receptor (H₄R) mRNA in synovial tissues of rheumatoid arthritis (RA) and osteoarthritis (OA) patients, and to study correlation of results with clinical characteristics of patients with RA. Synovial tissues were obtained from 7 RA and 7 OA patients undergoing artificial arthroplasty. Serum levels of erythrocyte sedimentation rate, C-reactive protein, matrix metalloproteinase-3 (MMP-3), rheumatoid factors, and cyclic citrullinated peptide antibodies were determined. The expression of H₄R mRNA in synovial tissues was determined by real-time polymerase chain reaction. Expression of H₁R and H₄R mRNA were significantly lower in RA compared with OA patients (P < 0.005), while expression of H₂R mRNA was comparable in both. While a significant negative correlation was found between H₄R expression and serum MMP-3 concentration (r = -0.70, P < 0.05), no correlation was found between MMP-3 and H₁R (r = -0.52) or H₂R (r = 0.23). This study supports the supposition that H₄R in synovial tissue may play a role in cartilage and bone destruction by influencing the secretion of MMP-3 in patients with RA.