Background: PEPT1 was proposed to be expressed only in inflamed colonic tissues in which it could contribute to inflammatory bowel disease (IBD) development by transporting bacterial peptides, such as muramyl dipeptide (MDP), that activate intracellular pattern recognition receptors, such as the nucleotide-binding and oligomerization domain 2. To better define the pathological relevance of this transporter, we analyzed PEPT1 expression during intestinal inflammation and studied the susceptibility of Pept1-deficient (Pept1−/−) mice to experimental colitis.
Methods: Wild-type and Pept1−/− mice were treated with dextran sulfate sodium and 2,4,6-trinitrobenzene sulfonic acid to induce colitis, and MDP-induced cytokine expression was studied in colonic tissue cultures. PEPT1 expression was characterized in mouse models of Crohn's disease–like ileitis (TnfΔARE/WT) or colitis (Il-10−/−, Il-10XTlr2−/−) and endoscopic tissue samples from descending colon of patients with IBD (n = 11) and controls (n = 17). Moreover, the prevalence of the PEPT1 single-nucleotide polymorphism rs2297322 was tested in German patients with IBD (n = 458) and controls (n = 452).
Results: PEPT1 expression was consistently reduced under condition of acute or chronic experimental inflammation. Wild-type and Pept1−/− mice revealed comparable susceptibility to dextran sulfate sodium–induced and 2,4,6-trinitrobenzene sulfonic acid–induced colitis, and MDP-induced cytokine expression was PEPT1-independent. PEPT1 expression levels were also decreased in descending colon of patients with IBD during acute inflammation, but the rs2297322 single-nucleotide polymorphism was not associated with IBD susceptibility in the German cohort.
Conclusions: PEPT1 expression is reduced during intestinal inflammation and PEPT1 is neither required for MDP-induced immune response nor is the PEPT1 rs2297322 single-nucleotide polymorphism associated with IBD susceptibility in our German cohort. These data strongly argue against a primary role of PEPT1 in the initiation or progression of IBD.
Article first Published online 27 February 2014
1Technische Universität München, ZIEL-Research Center for Nutrition and Food Science, Biochemistry Unit, Weihenstephan, Germany;
2Institute of Pathology, Charité-Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany;
3Institut Pasteur de Lille, Center for Infection and Immunity of Lille, Lille, France;
4Université Lille Nord de France, Lille, France;
5Centre national de la recherche scientifique, Unité Mixte de Recherche, Lille, France;
6Institut National de la Santé et de la Recherche Médicale, Lille, France;
7Technische Universität München, ZIEL-Research Center for Nutrition and Food Science, Biofunctionality Unit, Weihenstephan, Germany;
8Institute of Microbiology and Hygiene, Charité-Universitätsmedizin Berlin, Campus Benjamin-Franklin, Berlin, Germany;
9Center for Gastrointestinal Biology and Disease, University of North Carolina, Chapel Hill, North Carolina;
10Department of Gastroenterology, Infectiology and Rheumatology, Charité-Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany;
11Institute of Transfusion Medicine and Immunology, Medical Faculty Mannheim, Heidelberg University, German Red Cross Blood Service of Baden-Württemberg-Hessen, Mannheim, Germany;
12Else Kröner-Fresenius-Zentrum für Ernährungsmedizin (EKFZ) and ZIEL-Research Center for Nutrition and Food Science, Technische Universität München (TUM), Weihenstephan, Germany; and
13Department of Pediatrics, Klinikum rechts der Isar (MRI), Technische Universität München (TUM), Munich, Germany. T. Wuensch is now with Department of Cell and Molecular Biology, Karolinska Institute, von Eulersväg 3, Stockholm, Sweden.
Reprints: Hannelore Daniel, Dr., Technische Universität München, Lehrstuhl für Ernährungsphysiologie, Gregor-Mendel-Street 2, 85350 Freising-Weihenstephan, Germany (e-mail: email@example.com).
Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.ibdjournal.org).
The authors have no conflicts of interest to disclose.
Supported by the Deutsche Forschungsgemeinschaft (DFG) as part of the Research Training Group GRK1482 and DFG grant SCHU 1518/2-1 to S. Schulz and by NIH grants R01 DK53347 and P40 RR018603 to R. Balfour Sartor.
D. Haller and H. Daniel share last authorship.
Received November 17, 2013
Accepted January 09, 2014