Role of TLR4 in RAW264.7 macrophage inflammation induced by palmitic acid / 天津医药

ABSTRACT

objective To investigate the effect of toll-like receptor 4 (TLR4) in RAW264.7 macrophage inflammation induced by palmitic acid and its possible mechanisms thereof. Methods C57BL/6J male mice were fed normal (control group) or high-fat diet (high-fat group) for 18 weeks. The serum level of free fatty acids (FFA) and mRNA levels of inflammatory cytokines in visceral adipose (TNF-α, IL-6 and MCP-1) were detected. Then, palmitic acid (150μmol/L and 300 μmol/L) was applied to stimulate RAW264.7 macrophage, the mRNA expression and the secretion level of cytokines were detected. Meanwhile, TLR4 protein level, the nuclear translocation and intracellular level of NF-κB p65 were also detected. After TLR4 inhibition by siRNA transfection, the mRNA expression and the secretion level of cytokines were detected. Results The body weight and Lee's index were significantly higher in high-fat group than those of control group (P<0.05). The serum level of FFA and mRNA levels of inflammatory cytokines (TNF-α, IL-6 and MCP-1) in visceral adipose were significantly higher in high-fat group than those of control group (P<0.05). Compared with mice without FFA (BSA group), the mRNA expression and the levels of TNF-α, IL-6, and MCP-1 were significantly increased (P<0.05), and the protein expression of TLR4 and NF-κB phosphorylated protein were up-regulated (P<0.05) in mice treated with palmitic acid (150μmol/L and 300μmol/L). The nuclear translocation and intracellular level of NF-κB p65 were increased in mice treated with palmitic acid 300μmol/L than mice in BSA group (P<0.05). The mRNA levels of TNF-α, IL-6 and MCP-1 and their secretion level were significantly decreased after TLR4 siRNA transfection (P<0.05). Conclusion These results suggest that TLR4 may mediate the inflammation in RAW264.7 macrophage stimulated by palmitic acid by inducing inflammatory cytokines (TNF-α, IL-6 and MCP-1), and which may be related with the activation of NF-κB.