Fig. 4.

Functional role of single immunoglobulin (Ig) interleukin (IL)-1R-related molecule (SIGIRR) in Toll-like receptor (TLR)-4 signalling in colonic epithelial cells. (a) Representative results of flow cytometry showing expression of SIGIRR in SW480 and human monocytic leukaemia cell line (THP-1) cells. (b) Efficiency of SIGIRR siRNA for target gene expression knock-down in SW480 and THP-1 cells, as evaluated by real-time polymerase chain reaction (PCR). The level of SIGIRR expression in each of the samples was normalized by β-actin and compared to that of the negative control siRNA. Error bars indicate the standard error of mean values obtained from four independent experiments. #P < 0·01 versus negative control siRNA. (c) SIGIRR in colonic epithelial cells functions as a negative regulator in TLR-4 signalling. Cells were transfected with SIGIRR or control siRNAs, then cultured with or without lipopolysaccharide (LPS) (100 ng/ml) for 24 h, after which IL-8 contents in culture media were examined by enzyme immune assay (EIA). Error bars indicate the standard error of mean values obtained from four independent experiments. #P < 0·01 versus control siRNA. (d) Evaluation of nuclear factor (NF)-κB activities in SIGIRR siRNA-transfected SW480 cells after treatment with lipopolysaccharide (LPS). Firefly and renilla luciferase assays were performed with each sample, and the respective ratios were compared to that of the negative control siRNA. Error bars indicate the standard error of mean values obtained from four independent experiments. *P < 0·05 versus control siRNA.