Abstract: Objective To investigate the inhibitory effect of docosahexaenoic acid on macrophage inflammation induced by Porphyromonas gingivlis (P.g) lipopolysaccharide (LPS). Methods The cytotoxicity of DHA on RAW264.7 induced by P.g-LPS was tested by CCK-8 method. The P.g-LPS and RAW264.7 cells were cultured for 24 h to simulate the microenvironment of inflammation in vitro, then the culture medium containing DHA was replaced for 24 hours. The expressions of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) mRNA in RAW264.7 cells were detected by real-time quantitative PCR (qRT-PCR). The secretion of TNF-α, IL-1β and IL-6 in the cell supernatant was determined by enzyme-linked immunosorbent assay (ELISA). The production of reactive oxygen species (ROS) was detected by DCFH-DA method. Results 1mg/L P.g-LPS had no toxicity on RAW264.7 cells. DHA concentration above 100 μmol/L showed significant toxicity on RAW264.7 cells stimulated by P.g-LPS (P＜0.05). The mRNA expressions of TNF-α, IL-1β, IL-6 in the P.g-LPS group were significantly higher than those in the negative control group (P＜0.05). DHA of 25, 50 and 75 μmol/L reduced the expression of TNF-α, IL-1β, IL-6 mRNA and the synthesis of TNF-α, IL-1β, IL-6 (P＜0.05). The production of ROS in P.g-LPS group increased; 25, 50, 75 μmol/L DHA reduced the production of ROS (P＜0.05); the inhibition degree was concentration-dependent. Conclusion DHA can effectively inhibit the inflammatory response of macrophages induced by P.g-LPS.

Key words: docosahexaenoic acid, macrophage, Porphyromonas gingivlis lipopolysaccharide