Osteopontin as two-sided mediator of intestinal inflammation |
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Authors: | Heilmann Katja Hoffmann Ute Witte Ellen Loddenkemper Christoph Sina Christian Schreiber Stefan Hayford Claudia Holzlöhner Pamela Wolk Kerstin Tchatchou Elianne Moos Verena Zeitz Martin Sabat Robert Günthert Ursula Wittig Bianca Maria |
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Institution: | Medical Clinic 1 (Gastroenterology/Infectiology/Rheumatology), CharitéUniversity Medicine Berlin, Campus Benjamin Franklin, Germany;Interdisciplinary Group of Molecular Immunopathology Dermatology/Medical Immunology CharitéUniversity Medicine, Berlin, Germany;Institute for Pathology, CharitéUniversity Medicine Berlin, Campus Benjamin Franklin, Germany;First Medical Department, University Hospital Schleswig-Holstein, Campus Kiel, Germany;Institute for Pathology, University Hospital Basel, Switzerland |
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Abstract: | Osteopontin (OPN) is characterized as a major amplifier of Th1-immune responses. However, its role in intestinal inflammation is currently unknown. We found considerably raised OPN levels in blood of wild-type (WT) mice with dextran sodium sulfate (DSS)-induced colitis. To identify the role of this mediator in intestinal inflammation, we analysed experimental colitis in OPN-deficient (OPN(-/-)) mice. In the acute phase of colitis these mice showed more extensive colonic ulcerations and mucosal destruction than WT mice, which was abrogated by application of soluble OPN. Within the OPN(-/-) mice, infiltrating macrophages were not activated and showed impaired phagocytosis. Reduced mRNA expression of interleukin (IL)-1 beta and matrix metalloproteinases was found in acute colitis of OPN(-/-) mice. This was associated with decreased blood levels of IL-22, a Th17 cytokine that may mediate epithelial regeneration. However, OPN-(/-) mice showed increased serum levels of tumour necrosis factor (TNF)-alpha, which could be due to systemically present lipopolysaccharide translocated to the gut. In contrast to acute colitis, during chronic DSS-colitis, which is driven by a Th1 response of the lamina propria infiltrates, OPN(-/-) mice were protected from mucosal inflammation and demonstrated lower serum levels of IL-12 than WT mice. Furthermore, neutralization of OPN in WT mice abrogated colitis. Lastly, we demonstrate that in patients with active Crohn's disease OPN serum concentration correlated significantly with disease activity. Taken together, we postulate a dual function of OPN in intestinal inflammation: During acute inflammation OPN seems to activate innate immunity, reduces tissue damage and initiates mucosal repair whereas during chronic inflammation it promotes the Th1 response and strengthens inflammation. |
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Keywords: | Th1 immune response inflammatory bowel disease inflammation phagocytosis |
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