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J Hepatol. 2014 Apr;60(4):782-91. doi: 10.1016/j.jhep.2013.12.005. Epub 2013 Dec 11.

A TLR2/S100A9/CXCL-2 signaling network is necessary for neutrophil recruitment in acute and chronic liver injury in the mouse.

Author information

1
Fibrosis Research Group, Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, UK.
2
Division of Gastroenterology, Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA, USA.
3
Department of Pharmacology and Pathology Laboratory of Gene Regulation and Signal Transduction, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0723, USA.
4
Fibrosis Research Group, Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, UK. Electronic address: derek.mann@newcastle.ac.uk.

Abstract

BACKGROUND & AIMS:

Neutrophils are important immune effectors required for sterile and non-sterile inflammatory responses. However, neutrophils are associated with pathology in drug-induced liver injury, acute alcoholic liver disease, and ischemia-reperfusion injury. An understanding of the complex mechanisms that control neutrophil recruitment to the injured liver is desirable for developing strategies aimed at limiting neutrophil-mediated cellular damage.

METHODS:

Wt, tlr2(-/-), tlr4(-/-), and s100a9(-/-) mice were administered CCl4 either acutely (8, 24, 48, or 72 h) or chronically (8 weeks) and livers investigated by histological (IHC for neutrophils, fibrogenesis, proliferation, and chemotactic proteins) or molecular approaches (qRT-PCR for neutrophil chemoattractant chemokines and cytokines as well as pro-fibrogenic genes).

RESULTS:

Mice lacking TLR2 or S100A9 failed to recruit neutrophils to the injured liver and had a defective hepatic induction of the neutrophil chemokine CXCL-2. Hierarchy between TLR2 and S100A9 proved to be complex. While induction of S100A9 was dependent on TLR2 in isolated neutrophils, there was a more complicated two-way signalling cross-talk between TLR2 and S100A9 in whole liver. However, wound-healing and regenerative responses of the liver were unaffected in these genetic backgrounds as well as in wild type mice, in which neutrophils were depleted by infusion of Ly-6G antibody.

CONCLUSIONS:

We have identified TLR2 and S100A8/S100A9 as key regulators of hepatic CXCL-2 expression and neutrophil recruitment. This novel TLR2-S100A9-CXCL-2 pathway may be of use in development of new strategies for selectively manipulating neutrophils in liver disease without impairing normal wound healing and regenerative responses.

KEYWORDS:

Inflammation; Liver fibrosis; Neutrophil; S100A9; Toll like receptor

PMID:
24333183
PMCID:
PMC3960359
DOI:
10.1016/j.jhep.2013.12.005
[Indexed for MEDLINE]
Free PMC Article

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