Silke Kiessling © Silke Kiessling |
Impaired clock gene expression has been observed in biopsies from patients with Inflammatory Bowel Disease (IBD). Disruption of circadian rhythms, which occurs in shift workers, has been linked to an increased risk of gastrointestinal diseases, including IBD. The intestinal clock balances gastrointestinal homeostasis by regulating the microbiome. We aimed to characterise intestinal immune functions in mice lacking the intestinal clock and in IBD-relevant mouse models under different feeding conditions in order to assess the functional impact of the intestinal clock in the development of gastrointestinal inflammation.
Tissues and faecal samples from intestinal clock-deficient mice (Bmal1IEC-/-) and mouse models for colitis (IL-10-/-, Bmal1IEC-/-xIL-10-/-, DSS administration) under ad libitum and restricted feeding (RF) conditions were used to determine the causal role of the intestinal clock in colitis. Experiments involving faecal microbiota transfer into germ-free recipients were used to directly test the role of microbial rhythmicity in the progression and development of IBD.
Lack of the intestinal clock promoted gut inflammation and dramatically reduced survival in colitis models. Germ-free Bmal1IEC-/- hosts colonised with disease-associated microbiota exhibited increased inflammatory responses, suggesting the importance of the intestinal clock for IBD development. RF in IL-10-/- mice restored the colon clock and related immune functions, improved the inflammatory responses and rescued the histopathological phenotype. In contrast, RF failed to improve IBD symptoms in Bmal1IEC-/-xIL-10-/- mice, demonstrating the significance of the intestinal clock in gating the effect of RF.
We obtained evidence that inflammation-associated intestinal clock dysfunction triggers host immune imbalance and promotes the development and progression of IBD-like colitis. Enhancement of intestinal clock function by RF modulates the pathogenesis of IBD and thus could become a novel strategy to ameliorate the symptoms in IBD patients.