Inhibition of RAW264.7 macrophage inflammatory cytokines release by small hairpin RNAi targeting TLR4.

In order to construct an expression vector carrying small hairpin (sh) RNA (shRNA) for toll-like receptor 4 mRNA and a reporter gene of enhanced green fluorescence protein (EGFP) and study the inhibition of cytokine release by RAW264.7 cell induced by lipopolysaccharide (LPS) stimulation through transfection and expression of shRNA targeting TLR4 gene via the RNAi mechanism, the reporter gene plasmid pEGFP-C1 (4.7 kb) and psiRNA-hHlneo (2979 bp) were used. The H1 promotor and double Bbs I restrict endoenzyme site were cloned from plasmid psiRNA-hH1neo and reconstructed them into plasmid pEGFP-C1 in the Mlu I restrict endoenzymic site, forming plasmid pEGFP-H1/siRNA, which contained Bbs site and reporter EGFP gene. Then an oligonuclear hairpin sequence targeting TLR4 gene was designed by internet tool and inserted into the plasmid pEGFP-H1/siRNA forming plasmid pEGFP-H1/TLR4-siRNA. After transfection of pEGFP-H1/TLR4-siRNA into RAW264.7 cells, tumor necrosis factor-alpha (TNF-alpha) release by the cells after stimulation by LPS was detected. The results showed that the constructed pEGFP-H1/TLR4-siRNA carrying hairpin RNA for TLR4 gene and reporter EGFP gene were proven to be right by restriction endonuclease analysis. The expression of EGFP gene was (50.37+/-8.23) % and after transfection of the plasmid pEGFP-H1/ TLR4-siRNA the level of TNF-alpha released by RAW264.7 cell was down regulated. It was concluded that shRNA targeting TLR4 gene could inhibit the TNF-alpha release by RAW264.7 cells evoked by LPS.