HMGB1 Acts In Synergy With LPS In Activating Rheumatoid Arthritis Synovial Fibroblasts To Secret The Matrix Metalloproteinase

Rheumatoid arthritis (RA) is a complex multisystem disease.For some time synovial fibroblasts have been regarded simply as innocent synovial cells, mainly responsible for synovial homeostasis. However, during the past decade, a body of evidence has accumulated illustrating that rheumatoid arthritis synovial fibroblasts (RASFs) are active drivers of joint destruction in rheumatoid arthritis. Details regarding the intracellular signalling cascades that result in long-term activation and synthesis of proinflammatory molecules and matrix-degrading enzymes by RASFs have been analyzed. This expanded knowledge of the distinct role played by RASFs in the pathophysiology of rheumatoid arthritis has moved these fascinating cells to the fore, and work to identify targeted therapies to inhibit their joint destructive potential is underway.Objective:High-mobility group box chromosomal protein 1 (HMGB1) have been implicated in various inflammatory conditions, including arthritis.The aims of this study were to determine HMGB1 acts in synergy with LPS in activating arthritis synovial fibroblasts to secret the matrix metalloproteinase (MMPs)and elucidate the mechanism.Methods:Monolayer cultured human synovial fibroblasts Cell were isolated from patients with rheumatoid arthritis. Gene expression of MMP-1,MMP-3, MMP-13 and IL-6 was detected by RT-PCR. Cell proliferation experiments were analysed by flow cytometry. Protein levels of IL-6, MMP-3, and MMP-13 were measured by ELISA. Protein levels of signalling molecules were assayed by western blotting.Results:Flow cytometric analysis showed that synovial fibroblasts Cell proliferation up regulated expression levels via HMGB1/LPS stimulation. MMP-3,MMP-13 and IL-6 mRNA was constitutively expressed in synovial fibroblasts Cell, and was enhanced byHMGB1/LPS stimulation. MMP-1mRNA was slightly up regulated byHMGB1/LPS. we added blocking antibodies (Anti-TLR2, Anti-TLR4, and RAGE-Fc) 30 minutes before LPS and/or HMGB1 were added to the medium and measured the secretion and expression of matrix metalloproteinase, and results showed that both TLR4 and RAGE were involved.Results showed that HMGB1 signaled through RAGE to enhance the proinflammatory activity of LPS. We then used the protein inhibitors to inhabit the activation of MAPK proteins and NF-κB. Results showed that blockading the activation of NF-κB abolished the production of MMPs or IL-6, and blockading the activation of MAPK P38 partly inhibited the production of MMPs or IL-6.Conclusion our data indicate that HMGB1 acts in synergy with LPS in activating arthritis synovial fibroblasts to secret the matrix metalloproteinase, may signal through RAGE, and enhances the phosphorylation of MAPK p38 and the activation of NF-κB. The crosstalk between TLR4 and RAGE may lead to the enhancement of inflammatory responses and play some part in the degradation of articular cartilage in arthritis synovial fibroblasts.