Effect of serum amyloid A on microglial migration and its mechanism

To investigate the effect of serum amyloid A (SAA) on microglial migration and its mechanism,the migration ability of SAA-induced primary microglia and murine N9 microglia,and the effect of formyl peptide receptor 2 (FPR2) antagonist and TLR2 neutralizing antibody on SAA-induced migration of N9 microglia were all examined by Transwell assay. The expression changes of FPR2 and Toll-like receptor 2 (TLR2) in N9 microglia after SAA stimulation were detected by real-time PCR. The effect of SAA on the expression of downstream signaling pathway kinases in N9 microglia was detected by Western blot. The effect of signaling pathway inhibitors on SAA-induced N9 microglial migration was examined by Transwell assay. The results showed that SAA promoted the migration of primary microglia and N9 microglia in a concentration-dependent manner. FPR2 antagonist and TLR2 neutralizing antibody inhibited SAA-induced N9 cell migration. SAA promoted increased mRNA transcript levels of FPR2 and TLR2 in N9 microglia,and stimulated the activation of mitogen-activated protein kinases (MAPKs) and nuclear factor κB (NF-κB) signaling pathways in N9 microglia,as shown by increased extracellular regulated protein kinase (ERK),p38 and c-Jun N-terminal kinase (JNK) phosphorylation levels and decreased IκBα expression levels. Inhibitors of p38,JNK,and NF-κB signaling pathways inhibited SAA-induced migration of N9 microglia. The difference between the groups was statistically significant (P<0.05). These results indicate that SAA activates downstream p38,JNK,and NF-κB signaling pathways by acting on FPR2 and TLR2,thereby inducing microglia migration.