For example, harmful substances produced by the intestinal flora, such as lipopolysaccharides (LPS) produced by Gram-negative bacteria, can be recognized by TLR4, triggering inflammatory responses and oxidative stress, etc. In turn, the enhanced inflammatory response exacerbates the defective intestinal barrier, leading to colonic leakage and thus exacerbating IBD [51]. This evidence concerns the gene TLR4 and inflammatory bowel disease.