Abstract: Objective To investigate the effects of microRNA- 155 (miR-155) on immuno-inflammatory reaction of foam cells by targeting MyD88 and the possible mechanism. Methods RAW264.7 macrophages were cultured in vitro and transfected with miR-155 mimics, miR-155 inhibitor, MyD88 siRNA and their negative control respectively, then ox-LDL stimulation was given to build foam cell model. The expression of MyD88 in foam cells was detected by RT- qPCR and Western blot assay. Moreover, the expression levels of interleukin (IL)- 10, TGF- β1 and MCP- 1 in supernatant were determined by ELISA. Results After being transfected with miR- 155 mimics, the mRNA level of MyD88 remained unchanged compared with that of control group (P＞0.05). The protein level of MyD88 decreased significantly (P＜0.05), and the expression levels of IL-10, TGF-β1 and MCP-1 in supernatant also decreased significantly (P＜0.05). After being transfected with miR- 155 inhibitor, the mRNA level of MyD88 remained unchanged compared with that of control group (P＞0.05). The expression levels of MyD88 protein and inflammatory cytokines increased significantly (P＜0.05). After being transfected with MyD88 siRNA, the expression levels of MyD88 mRNA and protein decreased significantly, and the expression levels of inflammatory cytokines also decreased significantly (P＜0.05). Conclusion miR-155 can negatively regulate inflammation by targeting MyD88 through the inhibition of translation.

Key words: microRNAs, atherosclerosis, myeloid differentiation factor 88, foam cells, miR- 155, ox- LDL, inflammatory factor