Combinatorial Treatment with a Hif-Hydroxylase Inhibitor and Cyclosporine Provides Enhanced Protection in Colitis Through Improved Barrier Function

Background: Hypoxia is a prominent microenvironmental feature during active mucosal inflammation in ulcerative colitis patients (UC). HIF hydroxylases are key oxygen-sensing enzymes which link microenvironmental hypoxia to the control of inflammatory pathways. The pharmacologic HIF-hydroxylase inhibitor DMOG, which activates the HIF pathway, is protective in experimental colitis through the upregulation of genes promoting epithelial barrier function and preventing apoptosis. Cyclosporine, on the other hand, is protective through suppression of immune cell activation. Given the distinct barrier protective and anti-inflammatory roles of DMOG and cyclosporine respectively, we hypothesised that combining these drugs may provide an additive benefit in UC. Methods: The DSS model of colitis was used to determine the combinatorial efficacy of DMOG and cyclosporine. Caco2 cells were used to examine the effect of DMOG on transepithelial electrical resistance (TEER) and caspase activity. ZO-1 expression was analysed in cells as well as mouse and human colon tissue by immunofluorescence. Results: While both DMOG and cyclosporine ameliorated colitic disease progression in DSS treated mice, combinatorial treatment with both drugs simultaneously provided an additive benefit that surpassed the level of protection afforded by either drug alone as assessed by using multiple clinical and molecular markers of disease progression. The ability of DMOG to augment the anti-inflammatory effects of cyclosporine was predominantly due to preservation of barrier function and at least in part due to ZO-1 regulation specifically. Conclusions: Given their distinct mechanisms of action, we propose that combinatorial treatment with hydroxylase inhibitors and anti-inflammatory agents provide a new treatment strategy in UC. Figure: Combinatorial cyclosporine A (CyA) and DMOG provides additive protection in DSS colitis as demonstrated by disease activity index (Left) and colon shortening