P020. Silencing of prolyl hydroxylase 1 in intestinal microvascular endothelial cells prevents inflammation-induced endothelial dysfunction and dampens murine colitis
S. Van Welden1, D. Laukens1, L. Devisscher1, H. Devlies1, K. Olievier1, C. Correale2, S. D'Alessio2, S. Danese2, M. De Vos1, P. Hindryckx1, 1Ghent University, Department of Gastroenterology, Gent, Belgium, 2Humanitas Research Hospital, IBD Unit - Gastroenterology, Milano, Italy
Active inflammatory bowel disease (IBD) is characterized by extensive mucosal angiogenesis. However, these newly formed blood vessels are likely dysfunctional, as they are unable to resolve the inflammation-induced mucosal hypoxia. Prolyl hydroxylases (PHD1–3) are oxygen sensing enzymes that are actively involved in tumoral vascular dysfunction. We previously showed that the expression of PHD1, but not PHD2 and 3, is increased in inflamed biopsies of IBD patients. The aim was to characterize endothelial dysfunction in IBD patients and to investigate the role of PHD1, 2 and 3 in the vascular endothelium during experimental colitis.
The expression of endothelial dysfunction markers was analyzed by qRT-PCR in inflamed and non-inflamed colonic biopsies from IBD patients and compared to samples from healthy controls and infectious colitis patients. Human colonic microvascular endothelial cells were isolated from resection specimens and subjected to TNF to mimic inflammatory angiogenesis. The expression of endothelial dysfunction markers and PHD isoforms was analyzed. We then generated endothelial specific PHD1, PHD2 and PHD3 knock-out mice and subjected these mice to dextran sulfate sodium (DSS)-induced colitis.
Inflamed colonic biopsies from both UC and CD patients showed a significant up-regulation of the endothelial dysfunction markers ICAM-1, VCAM-1, vWF and VEGFR-2 (all p < 0.0001). Moreover, these markers all displayed a strong positive correlation with PHD1 (r = 0.667, r = 0.792, r = 0.731 and r = 0.747 respectively). TNF-stimulated endothelial cells showed a significant up-regulation of PHD1 (p < 0.01). In accordance, PHD1−/− cko mice had significantly less weight loss (p < 0.0001), reduced colon shortening (p < 0.01) and a lower histological inflammation score (p < 0.001) during DSS-induced colitis, when compared to the littermate controls. Furthermore, the PHD1−/− cko mice demonstrated a significant down-regulation of the endothelial dysfunction markers ICAM-1, VCAM-1, vWF and VEGFR-2 (all p < 0.05) in colonic lysates. Genetic inhibition of endothelial specific PHD2 and PHD3 had no effect on the course of DSS-colitis.
Our findings characterize a dysfunctional endothelial phenotype in IBD and show that selective silencing of PHD1 in microvascular colonic endothelial cells is sufficient to restore endothelial function and to dampen experimental colitis.