P106 Macrophages as a source of NOTCH Ligands in Crohn’s disease: implications in fibrosis

Abstract

Background Fibrosis constitute the main complications associated to Crohn′s disease (CD). NOTCH signalling has been implicated in lung, kidney, liver and cardiac fibrosis. Macrophages contribute to fibrosis through the release of different mediators and the pattern of secretion may vary according to their microenvironment. The aim of the present study is to analyze the role of NOTCH ligands derived from macrophages in the complications of CD. Methods The aim of the present study is to analyze the role of NOTCH ligands derived from macrophages in the complications of CD. We have analyzed: the protein expression of NOTCH ligands and receptors in CD patients with fistulizing (B3) and stenting pattern (B2), the protein expression of NOTCH ligands in macrophages treated with the main cytokines present in CD patients (IFNγ-, IL10-, IL4, TNFα-U937 treated cells), the protein expression of HES1 and fibrosis markers in DLL4-HT29 and DLL3-HT29 treated cells. Results are expressed as fold induction (mean±SEM). Statistical analysis was performed with one-way ANOVA followed by Newman-Keuls test or t-tet. Results The expression of DLL4 and NOTCH4 were significantly higher in intestinal samples from B3 CD patients (3,2 ± 0,6 N=4* and 3,8 ± 0,6 N=8*, respectively) than in B2 patients (1,6 ± 0,2 N=4 and 1,7 ± 0,3 N=8, respectively) and controls (1,0 ± 0,1N=3 and 1,0 ± 0,1 N=8, respectively). IFNγ-U937 treated cells increased significantly the protein expression of DLL3 and DLL4 (1,6 ± 0,09 N=6* and 1,3 ± 0,1 N=7*, respectively) respect vehicle; IL4 increased significantly the expression of DLL4 (1,4 ± 0,1 N=7*) and TNFα increased significantly the expression of DLL3 (1,4 ± 0,1 N=5*), respect vehicle. DLL4-HT29 treated cells increased significantly fibrosis markers (VIMENTIN: 1,7 ± 0,1 N=3*; SNAIL: 2,2 ± 0,2 N=3*) and HES1 (1,4 ± 0,06 N=3*), respect vehicle (1,0 ± 0,07 N=6; 1,0 ± 0,05 N=6; and 1,0 ± 0,05 N=6, respectively). DLL3-HT29 treated cells only produced a reduction in the protein expression of ECADHERIN (0,4 ± 0,1 N=3*), respect vehicle (1,0 ± 0,09 N=6). Conclusion Macrophages may act as a source of NOTCH ligands who could act as fibrosis mediators in CD patients with a fistulizing (B3) behavior. The microenvironment rich in IFNγ could activate the fibrosis process in epithelial cells by favoring the expression of DLL4 and DLL3 in macrophages. DLL4 mainly activates transcription factors involved in mesenchymal epithelial transition in colonic epithelial cells (SNAIL), while DLL3 seems to have a more relevant role in cell-cell junction modification (ECADHERIN).