Sialic acid exerts anti-inflammatory effect through inhibiting MAPK-NF-κB/AP-1 pathway and apoptosis in ulcerative colitis

Edible bird's nest is a natural food tonic and thought to be many health benefits. Sialic acid is the main bioactive component contributing to the biological activity of edible bird's nest. This study aimed to clarify the effect and mechanism of sialic acid on ulcerative colitis through dextran sulfate sodium induced colitis model and lipopolysaccharide stimulated RAW264.7 cell inflammation. The results revealed that sialic acid significantly reduced inflammation and MAPK phosphorylation in vivo. In vitro, sialic acid markedly inhibited the productions of pro-inflammatory cytokine, MAPK pathway activation, and the transcriptional activities of NF-κB and AP-1. In addition, Bcl-2/Bax ratio was increased and the activation of Cyt-c, Caspase-9 and Caspase-3 were decreased remarkably by sialic acid, suggesting sialic acid could inhibit cell apoptosis. Taken together, sialic acid exerts protective effect by regulating MAPK-NF-κB/AP-1 signaling pathways and apoptosis, and it might be a potential candidate for the prevention of ulcerative colitis.