Mucosal imbalance of interleukin-1β and interleukin-1 receptor antagonist in canine inflammatory bowel disease

Interleukin (IL)-1β is a key mediator of the inflammatory response. IL-1 receptor antagonist (IL-1Ra) regulates inflammation by functioning as an endogenous inhibitor of IL-1β. A disruption of the balance between IL-1β and IL-1Ra has been identified in human inflammatory bowel disease (IBD). The objective of this study was to determine whether there is an intestinal imbalance of IL-1β and IL-1Ra in canine IBD by comparing expression of IL-1β and IL-1Ra mRNA by real-time RT-PCR and expression of IL-1β and IL-1Ra protein by ELISA in 21 dogs with IBD, 15 dogs with intestinal lymphoma ('inflammatory' controls) and 20 healthy Beagles ('healthy' controls). A significant decrease in the intestinal IL-1Ra:IL-1β ratio of mRNA and protein was observed in IBD cases when compared with healthy control dogs. In contrast, a decrease in IL-1Ra:IL-1β ratio was not observed in dogs with intestinal lymphoma. The IL-1Ra:IL-1β protein ratio was negatively correlated with clinical severity in dogs with IBD. An intestinal imbalance between IL-1β and IL-1Ra production may play a role in the pathogenesis of canine IBD.