Suppression of type II collagen-induced arthritis by N-acetyl-L-cysteine in mice.

1. The antiarthritic and anti-inflammatory efficacy of N-acetyl-L-cysteine (NAC) was tested in male DBA/1 hybrid mice suffering from type II collagen-induced arthritis. Parameters including the arthritis index and the phagocytic responses recorded by chemiluminescence in unseparated blood were used for the assessment of disease activity. 2. Mice were immunized by subdermal injection of bovine type II collagen in Freund's complete adjuvant. The treatment with NAC started at day 42 after immunization and was continued over a period of six weeks: in doses ranging up to 50 mg/kg, a dose-dependent suppression of arthritis was noted; between 50 and 200 mg/kg, the inhibition curve had a plateau [ED50 = 50 mg/(kg x day)]. 3. The arthritis index correlated positively with the generation of chemiluminescence by reactive oxygen species (ROS) produced in neutrophils and monocytes activated by 12-O-tetradecanoylphorbol 13-acetate. 4. After treatment with 100 mg/kg of NAC from day 42 after immunization over a period of six weeks, the ROS production was reduced to levels occurring in whole blood of healthy animals. 5. It is concluded that low-molecular-weight antioxidants such as NAC may be adequate for controlling oxidative stress-derived damage in rheumatic diseases by modulation of ROS-dependent signal transduction pathways.