Structure and Immunological Characterization of the Capsular Polysaccharide of a Pyrogenic Liver Abscess Caused by Klebsiella pneumoniae: ACTIVATION OF MACROPHAGES THROUGH TOLL-LIKE RECEPTOR 4

Feng-Ling Yang,Yu-Liang Yang,Pei-Chun Liao,Ju-Ching Chou,Keng-Chang Tsai,An-Suei Yang,Fuu Sheu,Tzu-Lung Lin,Pei-Fang Hsieh,Jin-Town Wang,Kuo-Feng Hua,Shih-Hsiung Wu

doi:10.1074/jbc.m111.222091

Abstract

The active components of a primary pyrogenic liver abscess (PLA) Klebsiella pneumoniae in stimulating cytokine expression in macrophages are still unclear. The capsular polysaccharide (CPS) of PLA K. pneumoniae is important in determining clinical manifestations, and we have shown that it consists of repeating units of the trisaccharide (→3)-β-D-Glc-(1→4)-[2,3-(S)-pyruvate]-β-D-GlcA-(1→4)-α-L-Fuc-(1→) and has the unusual feature of extensive pyruvation of glucuronic acid and acetylation of C(2)-OH or C(3)-OH of fucose. We demonstrated that PLA K. pneumoniae CPS induces secretion of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) by macrophages through Toll-like receptor 4 (TLR4) and that this effect was lost when pyruvation and O-acetylation were chemically destroyed. Furthermore, expression of TNF-α and IL-6 in PLA K. pneumoniae CPS-stimulated macrophages was shown to be regulated by the TLR4/ROS/PKC-δ/NF-κB, TLR4/PI3-kinase/AKT/NF-κB, and TLR4/MAPK signaling pathways.

Highlights

Klebsiella pneumoniae is an opportunistic pathogen of the Enterobacteriaceae family and usually causes pneumonia or urinary tract infections
pyrogenic liver abscess (PLA) K. pneumoniae capsular polysaccharide (CPS) induced TNF-␣ secretion in splenocytes from wild-type mice, but not from Toll-like receptor 4 (TLR4)-deficient mice (Fig. 3F). These results strongly indicated that TLR4 is one of the cellular receptors for PLA K. pneumoniae CPS and that pyruvylation and acetylation of PLA K. pneumoniae CPS are essential for the cytokine induction activity
To examine whether PLA K. pneumoniae CPS-induced cytokine expression was associated with MAPK signaling cascades, phosphorylation levels of the MAPK p38, JNK1/2, and ERK1/2 in PLA K. pneumoniae CPS-stimulated macrophages were measured by Western blot analysis, and the results showed that phosphorylation levels of ERK1/2, JNK1/2, and p38 were increased compared with control cells and that little effect was seen with TFAtreated PLA K. pneumoniae CPS (Fig. 4A)

Summary

Introduction

Klebsiella pneumoniae is an opportunistic pathogen of the Enterobacteriaceae family and usually causes pneumonia or urinary tract infections. Pyruvation and Acetylation of PLA K. pneumoniae CPS Are Essential for Cytokine Induction—TNF-␣ and IL-6 are important pro-inflammatory cytokines produced mainly by activated macrophages and mediate multiple biological effects, including activation of immune responses.

Results

Conclusion