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Objective To evaluate the effect of linoleic acid on lipopolysaccharide (LPS)-induced release of inflammatory factors in the macrophages of mice.Methods The peritoneal macrophages obtained from C57BL/C mice were seeded in 24-well plates at a density of 4× 105 cells/well and in 6-well plates at a density of 2× 106cells/well.The cells were incubated and attached to the wall overnight in a 5％ CO2 incubator in humidity at 37 ℃.The experiment was performed in 2 parts.Part Ⅰ The cells in 24-well plates were randomly divided into 5 groups (n =8 each) using a random number table:control group (group C);LPS group;3 different concentrations of linoleic acid groups (LA1-3 groups).The sterile anhydrous alcohol 1 μl was added in group LPS,0.1,0.5 and 1.0 mol/ml linoleic acid 1 μl were added in LA1-3 groups,respectively,and 30 min later 100 μg/ml LPS 1 μ,l was added in LPS and LA1-3 groups.The culture medium was collected at 6 h after LPS administration to measure the concentrations of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in the supernatant by enzyme-linked immunosorbent assay.PartⅡ The cells in 6-well plates were randomly divided into 3 groups (n =6 each) using a random number table:control group (group C);LPS group;0.5 mol/ml linoleic acid group (group LA).The sterile anhydrous alcohol 1 μl was added in group LPS,0.5 mol/ml linoleic acid 1 μl was added in group LA,and 30 min later 100 μg/ml LPS 1 μl was added in LPS and LA groups.At 1 h after administration of LPS,the expression of Toll-like receptor 4 (TLR4) was determined by flow cytometry,and the expression of phosphorylated nuclear factor kappa B (NF-κB) p65 (p-NF-κB p65),phosphorylated extracellular signal-regulated protein kinase (p-ERK) and phosphorylated p38 mitogen-activated protein kinase (p-p38 MAPK) was determined by Western blot.Results Part Ⅰ Compared with group C,TNF-α and IL-6 concentrations in the supernatant were significantly increased in LPS and LA1 3 groups (P ＜ 0.05).Compared with group LPS,TNF-α and IL-6 concentrations in the supernatant were significantly decreased in LA1 3 groups (P＜0.05).Compared with group LA1,TNF-α and IL-6 concentrations in the supernatant were significantly decreased in LA2 and LA3 groups (P＜0.05).Compared with group LA2,TNF-α and IL-6 concentrations in the supernatant were significantly decreased in group LA3 (P ＜ 0.05).Part Ⅱ Compared with group C,the expression of TLR4,p-NF-κB p65,p-ERK and p-p38 MAPK in macrophages was significantly up-regulated in LPS and LA groups (P＜0.05).Compared with group LPS,the expression of TLR4,p-NF-κB p65,p-ERK and p-p38 MAPK in macrophages was significantly down-regulated in group LA (P＜0.05).Conclusion Linoleic acid can inhibit LPS-induced release of inflammatory factors in the macrophages of mice,and the mechanism may be related to the inhibition of TLR4 signaling pathway activation.