Up-regulation of IGF Binding Protein-3 Inhibits Colonic Inflammatory Response

The aggravating factors still remained unclear in inflammatory bowel disease (IBD). Despite many different therapeutic approaches, many patients do not respond to the therapy. The anti-inflammatory effect of insulin-like growth factor-binding protein-3 (IGFBP-3) was suggested because of its capability of nuclear factor-κB (NF-κB) signaling inhibition. Therefore, we hypothesized that the up-regulation of IGFBP-3 would inhibit an inflammatory process.

Lipopolysaccharides (LPS) treated intestinal epithelial cell 6 (IEC-6) and dextran sodium sulfate (DSS) induced colitis mice were used as colitis models. Exogenous IGFBP-3 expression was accomplished using the adenoviral vector system expressing IGFBP-3 (Ad/IGFBP-3). The inflammatory responses and relevant cellular responses in IEC-6 cells influenced by IGFBP-3 expression were evaluated by western blotting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and reactive oxygen species (ROS) measurement. The severity of colitis was evaluated with the colon tissues of DSS-induced mouse model.

We found that the IGFBP-3 expression reduced the production of inflammatory cytokines (cyclooxygenase-2, interleukin-1β, tumor necrosis factor-α) and ROS formation. IGFBP-3 expression also induced cell viability and inhibited NF-κB activation. In line with this data, the severity of DSS-induced mouse colitis was greatly ameliorated by the treatment of IGFBP-3 expressing adenoviral particles characterized with less weight loss and preserved colon length compared with the mice treated with DSS alone. The histopathology of the colon showed the reducing signs of colitis in Ad/IGFBP-3 treated DSS-mice group.

Therefore, our data suggest that Ad/IGFBP-3 up-regulation reduces colonic inflammatory response as a novel therapeutic protocol for IBD.