1002 Role of Intestinal Barrier Modulation By Non-Steroidal Anti-Inflammatory Drugs in Gluten-Induced Epithelial Damage in HLA-Dq8/Hcd4 Transgenic Mice

Abstract

Background: Transglutaminase 2 (TG2) is a multifunctional protein with transamidase as well as signaling activities. Its aberrant catalytic activity has been implicated in the pathogenesis of celiac sprue. However, the physiological role of TG2 and the mechanisms for its In Vivo activation in the small intestine are largely unknown. Aims: To study the TG2 catalytic activity under basal conditions and to identify signals that induce TG2 activity. Methods: We used selective TG2 inhibitors and tagged nucleophilic substrates to monitor the In Vivo TG2 activity during experimental conditions such as fibroblast scratch assay or methotrexate and polyinosinic-polycytidylic acid (poly(I:C)) administration in mice. Results: The majority of TG2 is inactive under normal physiological conditions in cell culture and In Vivo. However, abundant TG2 activity can be detected around the wound in a standard cultured fibroblast scratch assay. To induce tissue injury model in mice, we used methotrexate and poly(I:C), since they trigger small intestinal injury characterized by villous atrophy similar to celiac sprue. The acute poly(I:C) injury model, but not the methotrexate model, resulted in activation of the small intestinal TG2 and in cellular protein crosslinking. Conclusions: Extracellular TG2 is predominantly inactive under physiological conditions. It is activated upon tissue injury or in response to innate immune signals such us poly (I:C). Our results illustrate a new tool to investigate the biology of TG2 in the small intestine. They also provide convenient assays for evaluating small molecule inhibitors of extracellular TG2 activity In Vitro and In Vivo.