Suppression of collagen-induced arthritis by lipopolysaccharide in DBA/1 mice.

OBJECTIVE: Injection of lipopolysaccharide (LPS) has both promotion and inhibition effects on the autoimmune disease. Given the variable roles of LPS in autoimmune diseases, the role of LPS played in collagen-induced arthritis (CIA, autoimmune disease) model remains to be further determined. MATERIALS AND METHODS: CIA was induced by intradermal injection of collagen type II (CII) in DBA/1 mice (day 0) followed by a booster injection on day 21. Mice of CIA with LPS injection group (CIA+ LPS group) were intraperitoneally injected with 50 µg LPS on day 42. Tissues such as carpal joints and fingers were stained with hematoxylin and eosin (H&E) for histopathology analysis. Inflammation, pannus formation and bone resorption were monitored by a macroscopic scoring system. Serum level of IgG2a antibody was determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: The incidence of arthritis in CIA group was much higher than that in CIA+ LPS group (100%: 46.5%, p < 0.05), as same as the arthritis score (5.38:1.37, p = 8.16 × 10-6). Besides, the histopathologic score was also higher in CIA group than that in CIA+ LPS group (15.0:5.36). Compared with CIA group, mild synovial hyperplasia and no articular cartilage damage were observed in CIA+ LPS group. Besides, mice of CIA group produced a significantly higher level of IgG2a than CIA+ LPS group (3922 ng/ml: 2084 ng/ml, p = 0.0333) when arthritis developed. CONCLUSIONS: Our findings showed that LPS might suppress CIA progression under special conditions, opening up a new understanding of the roles of LPS in arthritis and new possibilities for a clinical therapy of CIA.