Salvia miltiorrhiza water-soluble extract, but not its constituent salvianolic acid B, abrogates LPS-induced NF-κB signalling in intestinal epithelial cells

Herbal medicine has become an increasing popular therapeutic alternative among patients suffering from various inflammatory disorders. The Salvia miltiorrhizae water-soluble extract (SME) have been shown to possess antioxidant and anti-inflammatory properties in vitro. However, the mechanism of action and impact of SME on LPS-induced gene expression is still unknown. We report that SME significantly abrogated LPS-induced I kappa B phosphorylation/degradation, NF-kappa B transcriptional activity and ICAM-1 gene expression in rat IEC-18 cells. Chromatin immunoprecipitation assay demonstrated that LPS-induced RelA recruitment to the ICAM-1 gene promoter was inhibited by SME. Moreover, in vitro kinase assay showed that SME directly inhibits LPS induced I kappa B kinase (IKK) activity in IEC-18 cells. To investigate the physiological relevance of SME inhibitory activity on NF-kappa B signalling, we used small intestinal explants and primary intestinal epithelial cells derived from a transgenic mouse expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-kappa B cis-elements (cis-NF-kappa B-EGFP). SME significantly blocked LPS-induced EGFP expression and I kappa B alpha phosphorylation in intestinal explants and primary IECs, respectively. However, salvianolic acid B, an activate component of SME did not inhibit NF-kappa B transcriptional activity and I kappa B phosphorylation/degradation in IEC-18 cells. These results indicate that SME blocks LPS-induced NF-kappa B signalling pathway by targeting the IKK complex in intestinal epithelial cells. Modulation of bacterial product-mediated NF-kappa B signalling by natural plant extracts may represent an attractive strategy towards the prevention and treatment of intestinal inflammation.