RESEARCH ARTICLE Conjugated linoleic acid protects against gliadin-induced depletion of intestinal defenses Paolo Bergamo 1 , Marta Gogliettino 2 , Gianna Palmieri 2 , Ennio Cocca 2 , Francesco Maurano 1 , Rosita Stefanile 1 , Marco Balestrieri 2 , Giuseppe Mazzarella 1 , Chella David 3 and Mauro Rossi 1 1 Istituto di Scienze dell’Alimentazione, Consiglio Nazionale delle Ricerche (CNR-ISA), Avellino, Italy 2 Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche (CNR-IBP), Napoli, Italy 3 Department of Immunology, Mayo Clinic College of Medicine, Rochester, MN, USA Received: May 2, 2011 Revised: July 1, 2011 Accepted: July 13, 2011 Scope: The involvement of oxidative stress in gluten-induced toxicity has been evidenced in vitro and in clinical studies but has never been examined in vivo. We recently demonstrated the protective activity of conjugated linoleic acid (CLA), which functions by the activation of nuclear factor erythroid 2-related factor2 (Nrf2), a key transcription factor for the synthesis of antioxidant and detoxifying enzymes (phase 2). Here, we evaluate the involvement of nuclear factor erythroid 2-related factor2 in gliadin-mediated toxicity in human Caco-2 intestinal cells and in gliadin-sensitive human leukocyte antigen-DQ8 transgenic mice (DQ8) and the protective activity of CLA. Methods and results: Gliadin effects in differentiated Caco-2 cells and in DQ8 mice, fed with a gliadin-containing diet with or without CLA supplementation, were evaluated by combining enzymatic, immunochemical, immunohistochemical, and quantitative real-time PCR (qRT- PCR) assays. Gliadin toxicity was accompanied by downregulation of phase 2 and elevates proteasome-acylpeptide hydrolase activities in vitro and in vivo. Notably, gliadin was unable to generate severe oxidative stress extent or pathological consequences in DQ8 mice intestine comparable to those found in celiac patients and the alterations produced were hampered by CLA. Conclusion: The beneficial effects of CLA against the depletion of crucial intestinal cyto- protective defenses indicates a novel nutritional approach for the treatment of intestinal disease associated with altered redox homeostasis. Keywords: Conjugated linoleic acid / Gluten toxicity / Nrf2-mediated defenses / Proteasome-acylpeptide hydrolase activity 1 Introduction Celiac disease (CD) is a chronic inflammatory pathology of the small intestine, resulting from a complex interplay between environmental and genetic factors [1]. Indeed, the main wheat gluten protein (gliadin) and related proteins from rye and barley represent the environmental factors responsible for the immunotoxic response in CD patients [2]. During the past few years, significant progress has been made in clarifying the different factors that contribute to the pathogenesis of CD. In addition, the presence of human Abbreviations: APEH, acylpeptide hydrolase; CD, celiac disease; CLA, conjugated linoleic acid; GCL, g-glutamylcysteine ligase; GFD, gluten-free diet; GSHtot, total thiols; GSSG, glutathione disulfide; GST, glutathione S-transferase; HO-1, heme oxyge- nase-1; IAP, intestinal alkaline phosphatase; MGFD, Modified GFD; NQO1, NAD(P)H:quinone oxidoreductase; Nrf2, nuclear factor erythroid 2-related factor 2; PC, protein-bound carbonyls; pt-glia, peptic–triptic digest of gliadin; StD, standard diet; tTG, tissue transglutaminase Correspondence: Dr. Paolo Bergamo, Istituto di Scienze dell’ Alimentazione, Consiglio Nazionale delle Ricerche (CNR-ISA), via Roma 64, 83100, Avellino, Italy E-mail: p.bergamo@isa.cnr.it Fax:139-825-299105 & 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.mnf-journal.com S248 Mol. Nutr. Food Res. 2011, 55, S248–S256 DOI 10.1002/mnfr.201100295