To evaluate the mechanism of macrophage-stimulating protein (MSP)-mediated inhibition of inflammatory cytokine and chemokine production in rheumatoid arthritis synovial fibroblasts (RASF).
RASF were treated with different concentrations (0, 0.5, 1, 5 and 10 ng/ml) of MSP with or without 1 μg/mL lipopolysaccharide (LPS). The protein expressions of IL-1β, TNF-α, IL-18, MIP-1, MCP-1, RANTES and PGE(2) were analyzed by enzyme-linked immunosorbent assays (ELISA). The total nitric oxide (NO) concentration was determined using the Griess reaction. The protein expressions of iNOS, COX-2, NF-κB(p-p65), IKB-α, IKB-β, p-P38, p-Erk1/2 (P-P42/44) and p-AKT were detected by Western blotting.
MSP markedly inhibited expression of inflammatory cytokines (IL-1β, TNF-α and IL-18), chemokines (MIP-1, MCP-1 and RANTES) and iNOS, NO, COX-2 and PGE(2) in RASF stimulated by LPS. MSP treatment decreased expressions of p-IκBα, p-IKBβ and p-P65 in RASF in a concentration-dependent manner. Expressions of p-AKT, p-p38 and p-Erk1/2 were also inhibited markedly in RASF stimulated by LPS after treatment with MSP in a concentration-dependent manner.
MSP could inhibit the inflammatory cycle by suppressing inflammatory mediators and activation of NF-κB as well. The inhibitory effect of MSP on LPS-stimulated RASF may act through suppression of multiple signals such as the PI3K/AKT and/or MAPK pathways.