Nitric oxide synthase inhibitor influences prostaglandin and interleukin-1 production in experimental arthritic joints

Objective: To assess involvement of nitric oxide (NO) in the increase in eicosanoid and interleukin-1 (IL-1) levels in the synovial fluid during antigen-induced arthritis (AIA) in rabbits treated with a competitive inhibitor of NO synthesis. Subjects: Thirteen New Zealand White rabbits were sensitized with 5 mg of methylated bovine serum albumin (mBSA). Arthritis was induced in the knee joint by injecting 0.5 ml of a sterile solution of mBSA (2 mg/ml) into the intra-articular cavity. Treatment: Prior to the induction of arthritis, the animals received N-Omega-Nitro-L-Arginine Methyl Ester (LNAME) or N-Omega-Nitro-D-Arginine Methyl Ester (DNAME) for 2 weeks, both at a dose of 20 mg/kg/day mixed with drinking water. Methods: Leukocyte efflux (total and differential white cell count), vascular permeability (Evans's blue method), synovial PMN cell infiltrate, and total nitrite (NO2.)/nitrate (NO3.) (HPLC), PGE(2), TxB(2), LTB(4) (radioimmunoassay), and IL-1 beta (ELISA) levels were quantified in the synovial fluid. Results: LNAME but not DNAME significantly suppressed leukocyte efflux and protein leakage into the articular cavity as well as synovial PMN cell infiltrate. Total NO2./NO3., PGE(2) and IL-1 beta levels were significantly reduced in the synovial fluid of LNAME treated animals. TxB(2) and LTB(4) were not affected by LNAME treatment. Conclusion: These data clearly show NO involvement in the IL-1-induced PGE(2) production in the synovial fluid of antigen-induced arthritis in rabbits.462727