Celiac.com 12/07/2016 - Refractory celiac disease (RCD) is a form of celiac disease that does not respond to treatment with gluten-free diet, and often involves greater risk of complications.
A team of researchers recently set out to determine whether RCD-related inflammation is marked by high Smad7, an intracellular inhibitor of transforming growth factor (TGF)-β1 activity. The research team included S Sedda, V De Simone, I Marafini, G Bevivino, R Izzo, OA Paoluzi, A Colantoni, A Ortenzi, P Giuffrida, GR Corazza, A Vanoli, A Di Sabatino, F Pallone, and G Monteleone. They are variously affiliated with the Department of Systems Medicine at the University of Rome "Tor Vergata," the First Department of Internal Medicine at the Fondazione IRCCS Policlinico San Matteo of the University of Pavia, and with the Department of Molecular Medicine at San Matteo Hospital at the University of Pavia in Pavia, Italy.
The team evaluated Smad7 in duodenal biopsy samples of patients with RCD, patients with active celiac, patients with inactive celiac disease and healthy controls by Western blotting, immunohistochemistry and real time-PCR. In the same samples, they used ELISA and immunohistochemistry to assess TGF-β1 and phosphorylated (p)-Smad2/3, respectively.
They evaluated pro-inflammatory cytokine expression in RCD samples cultured with Smad7 sense or antisense oligonucleotide. Smad7 protein, but not RNA, expression was increased in RCD, as compared to active and inactive celiac patients and healthy controls. This increased expression was associated with defective TGF-β1 signaling, as marked by diminished p-Smad2/3 expression. TGF-β1 protein content did not differ among groups. Knockdown of Smad7 in RCD biopsy samples reduced IL-6 and TNFα expression.
These results show that, in RCD, high Smad7 associates with defective TGF-β1 signaling, and sustains inflammatory cytokine production.
These results suggest a novel mechanism by which amplifies mucosal cytokine response in RCD, and suggest that treatments targeting Smad7 might be helpful in RCD.