Plant sterol guggulsterone inhibits nuclear factor-kappaB signaling in intestinal epithelial cells by blocking IkappaB 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)-1beta or lipopolysaccharide (LPS) with or without guggulsterone. The effects of guggulsterone on nuclear factor (NF)-kappaB signaling in IEC were examined by intercellular adhesion molecule (ICAM)-1 real-time reverse-transcription polymerase chain reaction, NF-kappaB transcriptional activity assay, Western blotting for IkappaB phosphorylation/degradation, electrophoretic mobility shift assay, and in vitro IkappaB 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 IkappaB and IKK in colon mucosa was assessed by Western blotting and immunohistochemistry. RESULTS: Guggulsterone significantly inhibited LPS- or IL-1beta-induced ICAM-1 gene expression, NF-kappaB transcriptional activity, IkappaB phosphorylation/degradation, and NF-kappaB 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 IkappaB and IKK phosphorylation induced by DSS was attenuated in guggulsterone-treated mice. CONCLUSION: Guggulsterone blocks NF-kappaB 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.