Bacterial Flora Play Important Roles in Acute Dextran Sulphate Sodium-Induced Colitis But Are Not Involved in Gal-3 Dependent Modulation of Colon Inflammation

An altered immune response to normal gut microflora is important for the pathogenesis of ulcerative colitis (UC). Galectin- 3 (Gal-3) is an endogenous lectin that plays an important pro-inflammatory role in the induction phase of acute colitis by promoting activation of the NLRP3 infl ammasome and production of IL-1β in macrophages. By using dextran sulphate sodium (DSS) induced colitis, a well-established animal model of UC, we determined whether Gal-3 affects the function of colon infiltrating macrophages by interfering with intestinal microfl ora. Our results showed that genetic deletion of Gal-3 significantly attenuates DSS-induced colitis by down-regulating infiltration of phagocytic cells (neutrophils, macrophages and dendritic cells) in colon tissue of DSS-treated mice, and this correlated with differences in bacterial flora of the gut. Antibiotic treatment attenuates DSS-induced colitis in WT and Gal-3-/- mice without affecting differences between the groups. In conclusion, Gram negative bacterial flora play an important role in DSS-induced acute colitis of mice but are not involved in Gal-3 dependent modulation of colon inflammation.