DOP53 PTPN2 and TiO2 in the pathogenesis of inflammatory bowel disease
J. Conde, M. Schwarzfischer, E. Katkeviciute, J. Häfliger, A. Niechcial, N. Brillant, K. Atrott, K. Bäbler, M. Scharl
Department of Gastroenterology and Hepatology, University Hospital Zurich, c/o University of Zurich, Zurich, Switzerland
Inflammatory bowel disease (IBD) is caused by a complex interaction among genetic, immunological, bacterial and environmental factors. In this scenario, protein tyrosine phosphatase non-receptor type-2 (PTPN2) has been recognised as a risk factor for the development of IBD and functional studies revealed a major role for this protein in the development of experimental colitis through the regulation of the inflammasome, among other processes. In the same way, a potential relationship between diet components and IBD was suggested. In fact, it was reported that the food additive titanium dioxide (TiO2) was able to induce inflammasome activation in vitro and increase colitis severity in vivo. These observations led us to hypothesise a putative relationship between PTPN2 and TiO2 that could explain the effects of this microparticle in the pathogenesis of bowel inflammation.
DSS colitis model was performed in mice lacking PTPN2 in myeloid cells and their wild-type littermates, treated or not with titanium dioxide. After that, histology studies, flow cytometry, expression analysis, ELISA and barrier function experiments were performed. Also, bone marrow-derived macrophages (BMDMs) were used for in vitro studies.
Titanium dioxide was able to exacerbate DSS-induced colitis, especially in mice lacking PTPN2 in myeloid cells. Flow cytometry analysis of the lamina propria revealed significant changes in different immune cell populations such as macrophages. In vitro experiments using BMDMs revealed that TiO2 induced the activation of the inflammasome. Also, this microparticle down-regulated the expression of the anti-inflammatory cytokine IL-10 and these effects were mainly mediated by JNK and ERK kinases.
The food additive titanium dioxide seems to play a negative role in colitis development by affecting the production of pro- and anti-inflammatory mediators in macrophages. This study reveals a new mechanism by which a certain component of the diet modulates intestinal inflammation.