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 H-4 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.