TLR4 and colitis: The nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways are important signaling transducers downstream of TLR4 [39,40] and studies show that TLR4 is significantly increased in UC patients [41], while reduced NF-κB and MAPK signaling pathway activation is associated with the remission of colitis in mice [42,43].