Polyene Phosphatidylcholine Interacting with TLR-2 Prevents the Synovial Inflammation via Inactivation of MAPK and NF-κB Pathways

Rheumatoid arthritis (RA) is a chronic autoimmune joint disease that causes cartilage and bone damage or even disability, seriously endangering human health. Chronic synovial inflammation has been shown to play a vital role in disease sustainability. Therefore, downregulation of synovial inflammation is considered to be an effective discipline for RA therapy. Polyene phosphatidylcholine (PPC) is a hepatoprotective agent, which was observed to inhibit inflammation in macrophages and prevent collagen-induced arthritis (CIA) of rats in our previous study. However, the underlying mechanism remains unclear. The present study further reported that PPC can inhibit synovial inflammation. In lipopolysaccharide (LPS)-stimulated primary synovial fibroblasts (SFs) of mice, PPC significantly decreased pro-inflammatory cytokines production while increasing anti-inflammatory cytokines level. In this process, PPC downregulated the expression of TLR-2 and their downstream signaling molecules such as MyD88, p-ERK1/2, p-JNK1/2, and p-P38 in MAPK pathway and p-IκBα and NF-κB-p65 in NF-κB pathway. Moreover, the inhibitory effect of PPC on the above molecules and cytokines was weakened after pre-treatment with TLR-2 agonist Pam3CSK4. In addition, PPC lost its anti-inflammatory effect and its suppressing capability on MAPK and NF-κB pathways in TLR-2^−/− primary SFs after exposure to LPS. Collectively, this study demonstrated that PPC can alleviate synovial inflammation through TLR-2-mediated MAPK and NF-κB pathways, which can be proposed to be a potential drug candidate for RA prevention.