TLR4 and irritable bowel syndrome: Indeed, studies in rat mucosal colonic tissues and human colon epithelial cell lines, showed that exposure to CRH decreases transepithelial resistance, increases the epithelium permeability to macromolecules, as well as induces TLR4 expression, a finding consistent with the high TLR4 expression found in peripheral blood of IBS patients [160,161,162].