TLR4 and ulcerative colitis: It was further supported by in vitro observations employing mouse macrophages stimulated with LPS, a specific stimulator of TLR4 signaling [51], in which a marked increase in the induction of cytokines (e.g. TNFα, IL-6) known to be induced by TLR-4 signaling and to play important role in the pathogenesis of ulcerative colitis [39], [52], was observed.