Supprimierung der Leukozytenadhäsion und der intestinalen Entzündung durch einen Endothelinrezeptor-Antagonisten im DSS-Maus-Modell chronisch entzündlicher Darmerkrankungen

Abstract

Background: Besides their vasoconstrictive properties, endothelins (ET) stimulate the expression of cell adhesion molecules on endothelial cells, which moderate leukocyte adhesion and infiltration into the tissue. Levels of ETs are increased in inflammatory bowel disease (IBD). In this study ET receptors were blocked therapeutically in murine dextrane sodium sulfate (DSS) colitis and the effect on leukocyte adhesion and inflammation was investigated. Methods: Chronic colitis was induced in female balb/c mice (20 – 22 g) by oral administration of 3% DSS in three cycles of 5 days. After the last cycle, the mice (n = 10) were treated for 5 days by daily i.p. injection (30 mg/kg) of a non-selective ET-receptor antagonist (Bosentan). On day 30 leukocyte adhesion, leukocyte velocity, and vessel diameters were measured in each 10 submucosal venules by intravital microscopy in isoflurane/N₂O narcosis. Leukocyte infiltration was assessed by myeloperoxidase (MPO) measurements. Inflammation was measured clinically using the disease activity index (DAI) and histologically by the Dieleman score. Results were compared with a healthy and a diseased control group (n = 10). The Kruskal — Wallis test was applied with p < 0.05 considered as significant. Results: Compared to healthy controls, leukocyte adhesion was significantly increased in DSS colitis (adherent leukocytes 23.7 ± 8.7 vs. 0.6 ± 0.4; rolling leukocytes 67.1 ± 30.2 vs. 24.9 ± 10.4/0.01 mm²/30 s), while leukocyte velocity was significantly decreased ( 19 ± 5.2 vs. 52.7 ± 13.1 µm/s). Treatment with endothelin antagonists significantly attenuated firm leukocyte adhesion ( 1.2 ± 0.8 ) and leukocyte velocity was significantly increased (91.5 ± 41.9) compared to diseased controls. Treatment with ETreceptor antagonists resulted in significantly diminished histological scores (8.7 ± 2.3 vs. 15.8 ± 3.6 pts.) as well as significantly decreased MPO activity ( 13.1 ± 4.2 vs. 75.1 ± 21.5U/g) and DAI (2.4 ± 1.3 vs. 5.2 ± 1.6 pts.) compared to diseased controls. Conclusion: Nonischemic chronic DSS colitis is ameliorated by therapeutic blockade of ET receptors. A possible mechanism is the reduction of leukocyte adhesion by the downregulation of cell adhesion molecules. The results show that ETs are potent inflammatory mediators. ETreceptor antagonists could become a therapeutic option in the treatment of patients with IBD.