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P015. The PA system controls inflammatory response during experimental colitis

M. Genua1, S. D'Alessio1, C. Correale1, V. Arena2, S. Vetrano1, S. Danese1

1Istituto Clinico Humanitas, Rozzano, Italy; 2Catholic University of Rome, Internal Medicine Department/Gastroenterology Division, Rome, Italy

Background: Fibrinolysis and inflammation are inter-linked processes that play a key role in the pathogenesis of several chronic inflammatory disorders including Crohn's disease (CD) and ulcerative colitis (UC), the two major forms of inflammatory bowel disease (IBD).

The urokinase plasminogen activator (uPA) and its receptor (uPAR) exert pleiotropic functions over the course of both physiological and pathological processes. uPA not only has a key role in fibrinolysis but also modulates the development of protective immunity. In addition, uPAR anchors uPA at the cell surface supporting extracellular matrix degradation and regulates cell migration, adhesion and proliferation, thus influencing the development of inflammatory and immune responses.

Aim of the present study is to evaluate the expression and function of uPA-uPAR system in experimental models of colitis.

Methods: The dextran sulfate sodium (DSS) and trinitrobenzene sulfonic acid (TNBS) were used as models of colitis. Expression of uPAR and uPA in healthy and colitic mice was assessed by Real-time. uPAR expression changes were further confirmed by western-blot analyses. Specificity of uPAR expression was investigated by both confocal microscopy and flow cytometry. The functional role of uPAR was examined in uPAR knock out (KO) mice. Colitis disease activity index (DAI) was calculated and intestinal damage evaluated by both endoscopy and histology.

Results: The expression levels of uPA and uPAR increased during both DSS and TNBS treatment, as measured by Real-Time (4–6 fold increase for uPAR, p < 0.01 and 2–6 fold increase for uPA, p < 0.01). Western Blot studies confirmed uPAR changes in colitic mice (6 fold increase, p < 0.01). Confocal microscopy and FACS analysis identified CD68+ cells as the major cell type expressing high levels of uPAR.

KO mice displayed higher weight loss and increased DAI (p < 0.01, at day 8 and 9 for DSS model; p < 0.05 at day 3 and 4 for TNBS model), compared to wild-type littermates. Histological and endoscopic score were significantly higher in KO mice (p < 0.05).

Conclusions: Our findings reveal the uPA-uPAR system as a new component involved in controlling inflammation. In particular, uPAR expression is up-regulated during colitis by CD68+ macrophage and its genetic deletion leads to detrimental inflammation. uPAR seems to play a protective role in the development of experimental colitis and modulation of the uPA-uPAR system could offer a new pathway to control intestinal inflammation.