Hydroxylases as therapeutic targets in inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a common and debilitating clinical disorder comprising ulcerative colitis and Crohn's disease. IBD occurs when inappropriate immunological activity in the intestinal mucosa results in epithelial barrier dysfunction leading to exposure of the mucosal immune system to luminal antigenic material. This in turn results in the cycles of inflammation and further barrier dysfunction which underlie disease progression. Although significant therapeutic advances have been made over the last decade, current immunosuppressive and anti-inflammatory treatments for IBD have significant limitations due to lack of treatment response in some patients and adverse effects, including increased risk of infection and malignancy. Recent studies using experimental models of IBD have identified that intracellular hydroxylases, a group of enzymes responsible for oxygen sensing and activation of adaptive transcriptional responses to hypoxia may represent a new class of therapeutic targets in IBD. Hydroxylase inhibitors are effective in ameliorating symptoms of colitis at least in part through the promotion of intestinal epithelial barrier function. The mechanism of this protection is due to activation of hypoxia-sensitive transcription factors, including the hypoxia-inducible factor (HIF) and nuclear factor kappa-B (NF-κB), which activate specific epithelial barrier-protective transcriptional programs. In this review, the mechanism(s) of action and the therapeutic potential of small molecule hydroxylase inhibitors for the treatment of IBD will be discussed.