Asperuloside inhibited epithelial-mesenchymal transition in colitis associated cancer via activation of vitamin D receptor.

BACKGROUND

Asperuloside is a natural compound extracted from various herbs with several bioactivities. Its effects on anti-inflammation and anti-tumor indicated that asperuloside might prevent colorectal cancer developing from inflammatory bowel diseases (IBD). But there were few reports about the efficacy and mechanism of asperuloside on improving colorectal cancer. It has been reported that vitamin D receptor (VDR) could regulate the expression of SMAD3. In previous study, asperuloside could significantly improve the expression of VDR and reduced Smad3 mRNA in IEC-6 cell.

PURPOSE

The present study was aimed to investigate the potential mechanism of asperuloside on inhibiting epithelial-mesenchymal transition (EMT) in colitis associated cancer.

STUDY DESIGN

First, in LPS-injured IEC-6 cell, asperuloside inhibited phosphorylated p65 (p-p65) level, improved VDR expression and reduced Smad3 mRNA. Second, we wonder the relationship between VDR signaling and nucleus factor-kappaB (NF-κB) signaling during asperuloside on reducing Smad3 mRNA. And then, the effect of asperuloside on inhibiting EMT development through VDR/Smad3 was investigated. Finally, we testified the effect of asperuloside on protecting against colitis associated cancer (CAC) by inhibiting EMT development through VDR/Smad3.

METHODS

Pyrrolidinedithiocarbamate ammonium (PDTC) was used for established NF-κB-inhibited IEC-6 cell. This cell was applied for investigating the relationship between NF-κB and VDR of asperuloside on inhibiting Smad3. VDR-inhibited cell was established by small interfering RNA (siRNA) of VDR and was employed to investigate the role of VDR for asperuloside on decreasing Smad3. Transforming growth factor β1 (TGFβ1) was used for inducing EMT/fibrosis in IEC-6 cell. TGFβ1-stimulated cell was used for testifying the effect of asperuloside on inhibiting EMT development. AOM/DSS-induced CAC was established to investigate the effect of asperuloside on suppressing cancer development.

RESULTS

Asperuloside inhibited the level of p-p65 which was up-regulated by LPS. Asperuloside could up-regulate VDR signaling and reduce Smad3 mRNA in NF-κB-knockdown IEC-6 cells. Asperuloside failed to reduce Smad3 mRNA due to VDR knockdown, which implied that asperuloside might down-regulate Smad3 mRNA dependently on activation of VDR signaling and independently on inhibiting NF-κB signaling. Asperuloside exhibited significant prevention of EMT development in TGFβ1-induced IEC-6 cell (EMT cell) and mice CAC. Asperuloside reduced the transform of epithelial phenotype into motile mesenchymal phenotype in EMT cell along with decreasing levels of EMT markers by inhibiting Smad3 mRNA via activation of VDR. In mice with CAC, expression of VDR in colon was improved by asperuloside. Symptoms of colitis, tumor number and tumor size were significantly inhibited by asperuloside. Suppressed EMT development was determined by reduced α-SMA expression and decreased mRNAs of several EMT markers.

CONCLUSION

Asperuloside might prevent CAC through inhibiting EMT development via regulation of VDR/Smad3 pathway.