Gastroenterology

Gastroenterology

Volume 139, Issue 6, December 2010, Pages 2093-2101
Gastroenterology

Basic—Alimentary Tract
Loss of Prolyl Hydroxylase-1 Protects Against Colitis Through Reduced Epithelial Cell Apoptosis and Increased Barrier Function

https://doi.org/10.1053/j.gastro.2010.06.068Get rights and content

Background & Aims

Hypoxia inducible factor (HIF) prolyl hydroxylase inhibitors are protective in mouse models of inflammatory bowel disease (IBD). Here, we investigated the therapeutic target(s) and mechanism(s) involved.

Methods

The effect of genetic deletion of individual HIF-prolyl hydroxylase (PHD) enzymes on the development of dextran sulphate sodium (DSS)–induced colitis was examined in mice.

Results

PHD1−/−, but not PHD2+/− or PHD3−/−, mice were less susceptible to the development of colitis than wild-type controls as determined by weight loss, disease activity, colon histology, neutrophil infiltration, and cytokine expression. Reduced susceptibility of PHD1−/− mice to colitis was associated with increased density of colonic epithelial cells relative to wild-type controls, which was because of decreased levels of apoptosis that resulted in enhanced epithelial barrier function. Furthermore, with the use of cultured epithelial cells it was confirmed that hydroxylase inhibition reversed DSS-induced apoptosis and barrier dysfunction. Finally, PHD1 levels were increased with disease severity in intestinal tissue from patients with IBD and in colonic tissues from DSS-treated mice.

Conclusions

These results imply a role for PHD1 as a positive regulator of intestinal epithelial cell apoptosis in the inflamed colon. Genetic loss of PHD1 is protective against colitis through decreased epithelial cell apoptosis and consequent enhancement of intestinal epithelial barrier function. Thus, targeted PHD1 inhibition may represent a new therapeutic approach in IBD.

Section snippets

Animals

PHD1−/−, PHD2−/+, and PHD3−/− mice against a mixed background strain of Swiss/129, which were used for these experiments have been previously described.19, 23, 24 None of the PHD knockout mice showed differential weight gain compared with wild-type mice.

DSS Colitis Model

The DSS model of colitis was used as described previously.17 Briefly, acute disease was induced by the treatment of mice with 5% DSS in their drinking water for ≤6 days. The disease activity index was determined according to the parameters

PHD1-Deficient Mice Are Protected Against DSS-Induced Colitis

Previous studies have shown that treatment with pan-hydroxylase inhibitors is protective in DSS-induced colitis in mice.17, 18 Those studies used broad-spectrum hydroxylase inhibitors such as DMOG because pharmacologic isoform-specific inhibitors are currently unavailable. To determine which PHD enzyme or multiple enzymes are responsible for the protective effects of pan-hydroxylase inhibition, we investigated the development of DSS-induced colitis in PHD1−/−, PHD2+/−, and PHD3−/− mice. We

Discussion

A common feature of all IBD regardless of the underlying cause is the loss of intestinal epithelial barrier function because of excessive epithelial cell death, an event that allows the nonspecific movement of luminal antigenic material into the submucosa.28 The resulting inflammatory response drives further barrier dysfunction and the symptoms associated with the disease, thus establishing a positive feed forward loop between developing inflammation and barrier dysfunction. The intestinal

Acknowledgments

The authors thank Prof Peter Ratcliffe (Oxford University) who contributed to the generation of the PHD knockout mice, Dimitri Scholz (University College Dublin) for imaging advice, Alfonso Blanco for technical flow cytometric support, and Janet McCormack for technical support for slide scanning.

M.M.T., E.P.C., and C.R.L. contributed equally to this study. M.S. and C.T.T. contributed equally to this study.

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    Conflicts of interest The authors disclose no conflicts.

    Funding This work was funded by grants from Science Foundation Ireland (to C.T.T.) and the Emmy Noether Program of the German Research Foundation (to M.S.). Further support was provided by EU COST action TD0901 and Systems Biology Ireland.

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