ABSTRACT
OBJECTIVE To observe the effects of chlorogenic acid on the activation of macrophage induced by lipopolysaccharide （LPS）， and to explore the role of triggering receptors expressed on myeloid cells-2 （TREM2） in the action. METHODS To find a suitable LPS concentration， the cells were cultured with 1， 10 and 100 ng/mL LPS for 24 h. The level of interleukin 6 （IL-6） in the cell culture supernatant and protein expression of inducible nitric oxide synthase （iNOS） in the cells were detected. To search for a suitable chlorogenic acid concentration， the cells were divided into control group， LPS group and three chlorogenic acid （0.01， 0.1 and 1 μmol/L）+LPS groups. The levels of tumor necrosis factor α （TNF-α） and IL-1β in the cell culture supernatant， the protein expressions of iNOS and TREM2 in the cells and cell viability were detected. To observe the effects of TREM2 in chlorogenic acid alleviating macrophage activation， TREM2-small interfering RNA （TREM2-siRNA） was taken to intervene in TREM2 protein expression. The cells were divided into control group， LPS group， chlorogenic acid+LPS group， TREM2-siRNA+chlorogenic acid+LPS group and SC-siRNA+chlorogenic acid+LPS group. After 24 h incubation， the levels of TNF- α and IL-1β in the cell culture supernatant and protein expressions of TREM2， iNOS and nuclear factor κB p65 （NF-κB p65） in the cells were detected. RESULTS 10 ng/mL LPS promoted IL-6 release and increased iNOS protein expression， and 10 ng/mL LPS was taken in the next experiments. Compared with the LPS group， 0.1 μmol/L chlorogenic acid decreased TNF-α jiaji1981@126.com and IL-1β levels， and down-regulated iNOS expression，meanwhile increased TREM2 expression without effect on cell viability， and 0.1 μmol/L chlorogenic acid was taken in the next experiments. Compared with the control group， the protein expressions of iNOS and NF- κB p65 in the LPS group were significantly increased （P＜0.05）； compared with the LPS group， the protein expressions of iNOS and NF- κB p65 in the chlorogenic acid+LPS group were significantly decreased， the protein expressions of TREM2 was significantly increased （P＜ 0.05）； compared with the chlorogenic acid+LPS group， the protein expressions of iNOS and NF-κB p65 of TREM2-siRNA+ chlorogenic acid+LPS group were significantly increased， the protein expressions of TREM2 was significantly decreased （P＜0.05）. TREM2-siRNA could significantly reverse the above effects of chlorogenic acid， while SC-siRNA did not significantly affect the above anti-inflammatory effects of chlorogenic acid. CONCLUSIONS Chlorogenic acid can inhibit the LPS-induced macrophage activation， and its anti-inflammatory may be mediated by TREM2 protein.