Cigarette smoke condensate extracts augment collagen-induced arthritis in mice.

Although cigarette smoking is a solid environmental risk factor for rheumatoid arthritis (RA) as revealed by epidemiological studies, the scientific basis has not been provided. Proinflammatory cytokines produced by synoviocytes are implicated in the pathogenesis of RA. As cigarette smoke condensate (CSC) is able to up-regulate the production of proinflammatory cytokines from human fibroblast-like synoviocytes, we studied the effect of CSC on induction of arthritis in the mouse model of collagen type II-induced arthritis (CIA). When mainstream CSC or sidestream CSC was administered into DBA/1J mice at the time of immunization with collagen and complete Freund adjuvant, CSC dose-dependently augmented the induction and clinical development of arthritis at both young and older mice. Peritoneal injected mainstream CSC one day before immunization also exhibited the augmenting effect, suggesting the systemic effect of CSC. These results support the etiological role of cigarette smoking in RA.