[Effect of lipopolysaccharide on expression of interleukin-6 in human synoviocyte from patients with rheumatoid arthritis].

Aim: To study the effects of lipopolysaccharide (LPS), the supernatant of U937 cells stimulated with LPS and dexamethasone on interleukin-6 (IL-6) expression in the synoviocyte from patients with rheumatoid arthritis (RA).

Methods: Fibroblast-like synoviocytes (FLS) from the joint tissue of patients with rheumatoid arthritis were cultured and incubated for 24 h with LPS (1 mg.L-1) or the supernatant of U937 cells stimulated with LPS (1 mg.L-1) for 24 h. Dexamethasone was added to the supernatant of U937 cells and FLS was incubated for 24 h. The expression of IL-6 protein was detected by radioimmunoassay. The mRNA expression of IL-6 was accessed by RT-PCR.

Results: The growth of FLS was not markedly affected by LPS, and the protein secretion and mRNA expression of IL-6 were not markedly changed in FLS treated with LPS. The IL-6 secretion and IL-6 mRNA expression were significantly increased in FLS cultured with the supernatant from U937 cell treated with LPS. Dexamethasone markedly inhibited the protein secretion and mRNA expression of IL-6 in FLS cultured with the supernatant from U937 cell stimulated with LPS. The inhibitory effects were increased as the concentration of dexamethasone increased.

Conclusion: LPS was not shown to directly affect the expression of IL-6 in FLS, but it indirectly causes the increase of the IL-6 expression in FLS by stimulating U937 cell. Dexamethasone can inhibit this increase of the IL-6 expression.