Plant sterol guggulsterone inhibits nuclear factor-kappa B signaling in intestinal epithelial cells by blocking I kappa B kinase and ameliorates acute murine colitis

Abstract

Background/Aims: The plant sterol guggulsterone has been shown to have anti-inflammatory properties. It remains unknown, however, whether guggulsterone is effective for the treatment of inflammatory bowel disease (IBD). Therefore, we investigated anti-inflammatory effects of guggulsterone on intestinal epithelial cells (IEC) and on experimental murine colitis models and elucidated its molecular mechanisms. Methods: Human Caco-2 cells and rat non-transformed IEC-18 cells were stimulated with interleukin (IL)-1 beta or lipopolysaccharide (LPS) with or without guggulsterone. The effects of guggulsterone on nuclear factor (NF)-kappa B signaling in IEC were examined by intercellular adhesion molecule (ICAM)-1 real-time reverse-transcription polymerase chain reaction, NF-kappa B transcriptional activity assay, Western blotting for I kappa B phosphorylation/degradation, electrophoretic mobility shift assay, and in vitro I kappa B kinase (IKK) assay For in vivo study, dextran sulfate sodium (DSS)-treated mice were fed with or without guggulsterone. Colitis was quantified by disease activity index and evaluation of macroscopic and microscopic findings. Phosphorylation Of I kappa B and IKK in colon mucosa was assessed by Western blotting and immunohistochemistry. Results: Guggulsterone significantly inhibited LPS- or IL-1 beta-induced ICAM-1 gene expression, NF-kappa B transcriptional activity, I kappa B phosphorylation/degradation, and NF-kappa B DNA binding activity in IEC. Moreover, guggulsterone strongly blocked IKK activity. Administration of guggulsterone significantly reduced the severity of DSS-induced murine colitis as assessed by clinical disease activity score, colon length, and histology Furthermore, tissue upregulation of I kappa B and IKK phosphorylation induced by DSS was attenuated in guggulsterone-treated mice. Conclusion: Guggulsterone blocks NF-kappa B signaling pathway by targeting IKK complex in IEC and attenuates DSS-induced acute murine colitis, which suggests that guggulsterone could be an attractive therapeutic option in the treatment of IBD.