Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA219

Poster Communications

Factor-inhibiting HIF (FIH) knockout enables an anti-inflammatory effect of HIFs in a mouse model of colitis-induced colon cancer

V. Schützhold1, J. Fandrey1, S. Winning1

1. Institute of Physiology, University of Duisburg-Essen, Essen, Germany.

Colorectal cancer is the fourth most common cause of cancer mortality worldwide (1) and can be promoted by inflammatory bowel diseases as chronic colitis. Inflammation as well as tumors induce hypoxia and enforce a gene expression response controlled by hypoxia-inducible factors (HIFs). HIF is regulated by prolyl hydroxylases and the asparaginyl hydroxylase FIH. HIF stabilization leads to a less severe inflammation in an acute colitis mouse model (2), but the role of HIF in colon cancer development and the importance of its regulator FIH are unknown. In our study we used a mouse model for chronic intestinal inflammation and colon cancer development. Mice are treated twice with the oncogene azoxymethane (AOM, 10 mg/kg body weight, i.p.) and with two 5-day/one 4-day phase of 1.5% dextran sodium sulfate (DSS) in the drinking water, which induces intestinal inflammation by destruction of the epithelial barrier. In a continuative experiment, the hydroxylase inhibitor dimethyloxaloylglycine (DMOG) is administered every second day of DSS-treatment (320 mg/kg body weight, i.p.) to study the effect of hydroxylase inhibition, which is protective in acute inflammation (2), in a chronic colorectal cancer model. We recorded the disease activity index (DAI) comprising weight loss, stool consistency, and fecal (pellet) bleeding (3) each day of inflammation and took samples for RNA and immunohistochemical analysis after 10 weeks. FIHfl/fl x VillinCre-/- (WT) and FIHfl/fl x VillinCre+/- (KO) mice were used to study the importance of FIH in epithelial cells. Values are means ± SEM, compared by unpaired t-test. We observed a strong increase in tumor development in mice treated with DSS compared to control mice that only received AOM administration (tumor number: 21.1±3.2 n=6 vs. 6.2±1.3 n=14, p<0.01), but no differences between WT and KO mice. However, the analysis of the DAI in the third DSS phase indicates a diverse DMOG-dependent disease progress: The total DAI of WT mice increased due to the DMOG-treatment (23.5±3.5 n=14 vs. 34.2±1.8 n=5, p<0.1), whereas the disease state of the KO mice was unaffected. On RNA level, WT mice treated with DSS and DMOG showed a more than 2-fold increase in Il-10 expression compared to control mice while there was no difference in KO mice. Additionally, DSS/DMOG-treated WT mice showed a higher infiltration of macrophages immunohistochemically detected by F4/80 expression than KO mice of the same experimental group. FIH knockout in colon epithelial cells might influence the inflammation status in chronic colitis under chemical pan-hydroxylase inhibition during acute inflammation phases. With these data we can conclude that stabilized HIF has an anti-inflammatory effect not only in acute colitis (2) but also in chronic colitis and colorectal cancer development as simulated in our AOM/DSS mouse model.

Where applicable, experiments conform with Society ethical requirements