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.