Selective inhibition of cyclooxygenase 2–generated prostaglandin E2 synthesis in rheumatoid arthritis synoviocytes by taurine chloramine

OBJECTIVE: To investigate the effects of taurine chloramine (Tau-Cl), a chlorinated derivative of the amino acid taurine, on the expression of cyclooxygenase (COX) isoenzymes and prostaglandin E(2) (PGE(2)) synthesis in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS). METHODS: FLS, isolated from the synovial tissue of RA patients, were treated in vitro with either interleukin-1beta (IL-1beta; 1 ng/ml) alone or together with 200-500 microM Tau-Cl. The expression of COX isoenzymes was evaluated at both the protein (Western blotting) and the messenger RNA (mRNA) (reverse transcriptase-polymerase chain reaction) levels. The concentration of PGE(2) was measured by competitive acetylcholinesterase enzyme immunoassay. RESULTS: Resting FLS expressed mRNA encoding both COX-1 and COX-2, but only COX-1 was present at the protein level. These cells produced negligible amounts of PGE(2). Upon stimulation with IL-1beta, elevation of COX-2, but not COX-1, mRNA and protein preceded the enhancement of PGE(2) synthesis. In the presence of 300-400 microM Tau-Cl, significant inhibition of IL-1beta-triggered COX-2 mRNA and protein, and a related decrease in PGE(2) production, was observed. In contrast, no significant changes in COX-1 mRNA and protein levels were noted. CONCLUSION: Tau-Cl inhibits IL-1beta-triggered elevation of COX-2 and generation of PGE(2) by RA FLS. These results expand the spectrum of known antiinflammatory activities of this compound.