BACKGROUND & AIMS: Ileal bile acid malabsorption is present in Crohn's ileitis. The molecular mechanisms of regulation of the apical sodium-dependent bile acid transporter (ASBT) by inflammatory cytokines in vitro and in vivo are investigated. METHODS: Transient transfection studies of the human, mouse, and rat ASBT promoters and Northern analyses were performed in cells treated with the inflammatory cytokines and/or various activator protein-1 constructs. Rat ASBT promoter transgenic, wild-type, and c-fos-null mice were treated with indomethacin to assess the response to acute inflammation of the ileal mucosa. RESULTS: In Caco-2 cells, ASBT messenger RNA expression was reduced 65% after interleukin-1beta treatment, while c-fos and c-jun were up-regulated 2-fold. Human ASBT promoter activity was enhanced by c-jun and repressed by a dominant negative c-jun, c-fos, or a dominant negative c-fos. Meanwhile, c-fos antisense treatment activated the human ASBT promoter 5-fold and not only abrogated interleukin-1beta-mediated repression but led to a paradoxical increase in ASBT promoter activity. Indomethacin-induced acute ileitis led to repression of ASBT in wild-type mice and in the transgenic rat ASBT promoter reporter, while paradoxical activation of ASBT was seen in c-fos-null mice. Indomethacin-induced ileal injury was greater in the c-fos-null mice compared with the wild-type littermates. CONCLUSIONS: Human, rat, and mouse ASBT is inhibited by inflammatory cytokines via direct interactions of c-fos with the ASBT promoter.
BACKGROUND & AIMS: Ileal bile acid malabsorption is present in Crohn's ileitis. The molecular mechanisms of regulation of the apical sodium-dependent bile acid transporter (ASBT) by inflammatory cytokines in vitro and in vivo are investigated. METHODS: Transient transfection studies of the human, mouse, and ratASBT promoters and Northern analyses were performed in cells treated with the inflammatory cytokines and/or various activator protein-1 constructs. RatASBT promoter transgenic, wild-type, and c-fos-null mice were treated with indomethacin to assess the response to acute inflammation of the ileal mucosa. RESULTS: In Caco-2 cells, ASBT messenger RNA expression was reduced 65% after interleukin-1beta treatment, while c-fos and c-jun were up-regulated 2-fold. HumanASBT promoter activity was enhanced by c-jun and repressed by a dominant negative c-jun, c-fos, or a dominant negative c-fos. Meanwhile, c-fos antisense treatment activated the humanASBT promoter 5-fold and not only abrogated interleukin-1beta-mediated repression but led to a paradoxical increase in ASBT promoter activity. Indomethacin-induced acute ileitis led to repression of ASBT in wild-type mice and in the transgenic ratASBT promoter reporter, while paradoxical activation of ASBT was seen in c-fos-null mice. Indomethacin-induced ileal injury was greater in the c-fos-null mice compared with the wild-type littermates. CONCLUSIONS:Human, rat, and mouseASBT is inhibited by inflammatory cytokines via direct interactions of c-fos with the ASBT promoter.
Authors: Alexander L Ticho; Pooja Malhotra; Pradeep K Dudeja; Ravinder K Gill; Waddah A Alrefai Journal: Compr Physiol Date: 2019-12-18 Impact factor: 9.090
Authors: Fadi Annaba; Ke Ma; Pradeep Kumar; Amish K Dudeja; Rhonda D Kineman; Benjamin L Shneider; Seema Saksena; Ravinder K Gill; Waddah A Alrefai Journal: Am J Physiol Gastrointest Liver Physiol Date: 2010-07-22 Impact factor: 4.052
Authors: Nathan J Cherrington; Teresa E Estrada; Harrison A Frisk; Mark J Canet; Rhiannon N Hardwick; Bohuslav Dvorak; Katie Lux; Melissa D Halpern Journal: Am J Physiol Gastrointest Liver Physiol Date: 2012-11-01 Impact factor: 4.052