Interaction of Toll-like receptors with bacterial components induces expression of CDX2 and MUC2 in rat biliary epithelium in vivo and in culture

Abstract

The mechanism of transformation of biliary epithelium leading to intestinal metaplasia, which is significantly involved in biliary diseases, remains unclear. CDX2, an intestine-specific transcription factor, is thought to regulate intestinal mucin MUC2 (mucus core protein) expression. We took advantage of polycystic kidney (PCK) rats as a model of chronic suppurative cholangitis with intestinal metaplasia and of cultured biliary epithelial cells (BECs) from PCK rats to clarify the causal relation between bacterial components such as pathogen-associated molecular patterns (PAMPs) and the development of intestinal metaplasia of bile ducts. Histological, immunohistochemical, and in situ hybridization studies were conducted in PCK rat livers. In cultured BECs, CDX2 and MUC2 were expressed following treatment with PAMPs and inhibitors (anti-Toll-like receptor (TLR)2/TLR4 antibody, nuclear factor-kB (NF-kB) inhibitor MG132). Chronic suppurative cholangitis with intestinal metaplasia developed as the PCK rats aged, and intestinal metaplasia and aberrant CDX2 and MUC2 expression developed in parallel. Intraluminal bacteria and the expression of TLR2 and TLR4 in BECs were demonstrated in the bile ducts, showing chronic suppurative cholangitis. In cultured BECs, treatment with PAMPs induced upregulation of CDX2 and MUC2 expression, and this effect was abolished by pretreatment with anti-TLR2 and anti-TLR4 antibody and MG132. A knockdown of CDX2 by CDX2 small interfering RNA inhibited MUC2 expression in cultured BECs induced by PAMPs, and transfection of CDX2 expression vector induced MUC2 expression. In conclusion, bacterial components may induce upregulation of the CDX2 expression followed by MUC2 expression via TLR and the NF-kB system in cultured BECs, and could be related to the development of intestinal metaplasia of the bile ducts. Intestinal metaplasia associated with the aberrant expression of MUC2 1-4 is reportedly involved in tumorigenesis in several organs. Recent studies revealed that CDX2, a caudalrelated homeobox gene encoding an intestine-specific transcription factor, is a regulatory factor of intestinal development and expression of intestinal genes including MUC2 and is involved in intestinal metaplasia. 2,4,5-8 CDX2-dependent intestinal metaplasia is noted in Barrett's esophagus with MUC2 expression, and bile acid and chronic acid exposure have been reported to induce CDX2 expression. 2,[4][5][6]8,9 Intestinal metaplasia is also involved in the pathogenesis of biliary diseases. For example, in chronic cholangitis such as hepatolithiasis, intestinal metaplasia with goblet cells occurs, and MUC2 is aberrantly expressed in goblet cells colocalized with CDX2.

The Riddle of Nonalcoholic Fatty Liver Disease: Progression From Nonalcoholic Fatty Liver to Nonalcoholic Steatohepatitis

“…Subsequent to TLR2 and TLR4 activation, Homeobox protein CDX-2 and mucus core protein-2 expression increases. 115,116 The progression of NAFLD in humans has been related to the increase in bile ductules, and their senescence markers. Moreover, such senescent bile ductules express chemotactic protein, such as Monocyte chemotactic protein 1 (MCP-1), which are likely responsible for HSC activation.…”

“…114 Murine biliary cells express CD14, MD-2, and TLR2, 3, 4, and 5 and after LPS stimulation, murine biliary cells activates the NF-kB pathway and synthesized TNFa. 115 Human biliary epithelial cells express TLR 1 to TLR10. Subsequent to TLR2 and TLR4 activation, Homeobox protein CDX-2 and mucus core protein-2 expression increases.…”

Toll-Like Receptor 2 andMuc2Expression on Human Intestinal Epithelial Cells by Gymnophalloides seoi Adult Antigen

“…TLR2 signaling may enhance the physical barrier function of IECs (Akira and Takeda, 2004;Cario et al, 2004). Interestingly, Ikeda et al (2007) reported that pre-incubation of rat biliary epithelial cells with anti-TLR4 or anti-TLR2 antibodies downregulated MUC2 expression induced by LPS. In contrast, TLR2 and bacterial components induced expression of MUC2 in cultured gastric epithelial cell lines and were activated by nuclear factor (NF)-kB (Ding et al, 2005;Ikeda et al, 2007).…”

“…Interestingly, Ikeda et al (2007) reported that pre-incubation of rat biliary epithelial cells with anti-TLR4 or anti-TLR2 antibodies downregulated MUC2 expression induced by LPS. In contrast, TLR2 and bacterial components induced expression of MUC2 in cultured gastric epithelial cell lines and were activated by nuclear factor (NF)-kB (Ding et al, 2005;Ikeda et al, 2007). All of these results, including ours, suggest that G. seoi antigen induces MUC2 expression via the activation of the TLR pathways in human IECs.…”

“…TLR signaling is suppressed by MUC1 (human) and Muc1 (non-human species), and it may play a crucial role in airway infection by various pathogenic bacteria and viruses (Ueno et al, 2008). In rat biliary epithelia, treatment with anti-TLR2 antibodies or anti-TLR4 antibodies downregulated MUC2 expression that had been induced by lipopolysaccharide (LPS) (Ikeda et al, 2007). Kraft et al (2008) suggested that the TLR2 signaling pathway is involved in MUC5AC expression in airway epithelial cells exposed to Mycoplasma pneumoniae.…”