CD14 gene silencing alters the microRNA expression profile of RAW264.7 cells stimulated by Brucella melitensis infection.

Innate recognition of Brucella spp. is a key step in the activation of inflammation. CD14 binds PAMPs and is involved in LPS-induced pro-inflammatory cytokine release. Previously we showed that knock down of CD14 in RAW264.7 macrophages disrupted Brucella-host interactions. However, its effect on the macrophage microRNA (miRNA) expression profile, especially after stimulation by Brucella infection, is still unclear. To identify miRNAs involved in the macrophage response to Brucella infection, we performed miRNA expression profiling of CD14 knock-down RAW264.7 (224.3) macrophages infected with Brucella melitensis, and demonstrated, for the first time, that CD14 knock down significantly up-regulated the expression of mmu-miR-199a-3p and mmu-miR-183-5p in these conditions. These miRNAs have a well-characterized association with the target genes involved in immune response, inflammatory response, innate immune response, apoptosis processes, anti-apoptosis, cytokine production and cytokine-mediated signaling pathways. Among the 104 inflammation-related candidate target genes of mmu-miR-199a-3p and mmu-miR-183-5p in the 224.3+ B. melitensis group cells, the expression of the Cbl-b, a potential target of mmu-miR-199a-3p, was confirmed to be down-regulated using qRT-PCR and Western blot analysis. Our findings suggest that CD14 functions in the Brucella-host interaction may be through altered miRNA expression, and regulation of Cbl-b proteins.