Antikörperblockade von VLA-4 beeinflusst die Leukozyten-Endothelzell-Interaktion und wirkt entzündungshemmend im DSS-Mausmodell chronisch entzündlicher Darmerkrankungen

Abstract

Background: Very late antigen 4 (VLA-4; alpha 4 beta 1 integrin) is upregulated on the surface of circulating leukocytes in case of inflammation processes and mediates leukocyte firm adherence on endothelial cells by interaction with its ligand vascular cell adhesion molecule 1 (VCAM-1) [1]. We examined 1) if a monoclonal antibody (MAb) vs. VLA-4 reduces in vivo leukocyte adhesion and 2) if established colitis is reduced by blocking VLA-4 in a murine model of inflammatory bowel disease (IBD). Methods: Chronic colitis was induced in male balb/c mice (20 – 22 g) by oral administration of 3% dextrane sodium sulfate (DSS) [2]. In the first study, in 7 animals leukocyte adhesion was measured in a single colonic submucosal venule by intravital microscopy on day 30 [3]. Anti-VLA-4 (PS/2) 2 mg/kg was injected and leukocyte adhesion was observed for 60 min. In the second study mice were treated by daily i.p. injection of PS/2 2 mg/kg over 5 days. On day 30 disease activity index (DAI) and histology (Dieleman score [4]) were compared with a healthy and a diseased control group (n = 7). Furthermore, intravital microscopy was performed in 10 submucosal venules in the distal colon and leukocyte adhesion was evaluated. The Kruskal-Wallis test and Wilcoxon test were applied when appropriate (p < 0.05). Results: Leukocyte firm adherence was reduced several minutes after injection of PS/2 (16.0 ± 1.4 vs. 23.5 ± 2.2/0.01 mm²/30 s, p < 0.05) and further declined to 3.6 ± 1.0 at the end of the 60 min. Rolling leukocytes were diminished significantly from 154.2 ± 15.5 to 119.3 ±17.3 after 10 min of observation. Therapeutic treatment with anti-VLA-4 significantly reduced DAI (1.0 ±0.2 vs. 1.9 ±0.2 pts.), histological inflammation in the distal colon (13.5 ± 1.0 vs. 20.8 ±1.0 pts.) and the number of firm adherent leukocytes (1.8 ± 0.3 vs. 25.5 ± 3.7/0.01 mm²/30 s) compared to diseased controls. Rolling leukocytes were not reduced significantly. Conclusions: The VLA-4/VCAM-1 mediated leukocyte endothelial cell interaction plays a key role in the perpetuation of DSS-induced chronic colitis. VLA-4 has its major function in firm leukocyte adherence. Blockade of VLA-4 reduces established colitis and could thus become a therapeutical option in the treatment of patients with IBD.