Altered biliary epithelial cell and monocyte responses to lipopolysaccharide as a TLR ligand in patients with primary biliary cirrhosis

Abstract

Objective. Lipopolysaccharide (LPS) is suspected to trigger primary biliary cirrhosis (PBC) in susceptible individuals, yet the precise mechanism of its effect in PBC remains largely unknown. The aim of this study was to investigate altered responses to LPS ligand for Toll-like receptors (TLRs) in pathogenesis of PBC in vivo and in vitro. Material and methods. In vivo, we investigated levels of LPS and pro-inflammatory cytokines in sera and expression of LPS receptors in liver tissues from 162 patients with PBC, 325 patients with other liver diseases and 80 healthy controls. In vitro, altered responses to LPS on monocytes and cultured human biliary epithelial cells (BECs) from patients with PBC were determined. Results. Significantly higher levels of LPS in patients with PBC were detected, compared with patients with other liver diseases and healthy controls. Immunohistochemically, expression of TLR4, CD14, CD68 and NF-κB was significantly enhanced in liver tissues from patients with PBC. Before LPS stimulation, we found significantly higher serum levels of tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-8 in patients with PBC than those in healthy controls. After LPS stimulation, TLR4 expression and pro-inflammatory cytokine production in CD14-positive monocytes and cultured BEC from patients with PBC increased significantly. Conclusions. These results indicated that patients with PBC were prone to exhibit higher serum LPS level, hypersensitivity of monocytes and BEC to LPS, and enhanced production of pro-inflammatory cytokines. LPS altered expression of TLR4, CD14 and NF-κB on monocytes and BEC, which may be implicated in the pathogenesis and progression of PBC.

Key Words::

• Lipopolysaccharide
• primary biliary cirrhosis
• pro-inflammatory cytokines
• Toll-like receptor 4

Acknowledgements

The project was supported by the Capital (Beijing) Medicine Development and Research Foundation (2007-3035). We thank K. Harada, Y. Nakanuma (Department of Human Pathology, Kanazawa University Graduate School of Medicine, Kanazawa 920-8640, Japan) for kindly bestowing human BEC lines. We also thank J. Yang, Hai'ou Niu, S. Liu, Y. Zhao and L. Xiong for their excellent technical assistance.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.