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Research Paper

Formyl peptide receptor 2 orchestrates mucosal protection against Citrobacter rodentium infection

ORCID Icon, , , , , , , & show all
Pages 610-624 | Received 15 Jan 2019, Accepted 19 Jun 2019, Published online: 04 Jul 2019
 

ABSTRACT

Citrobacter rodentium is an attaching and effacing intestinal murine pathogen which shares similar virulence strategies with the human pathogens enteropathogenic- and enterohemorrhagic Escherichia coli to infect their host. C. rodentium is spontaneously cleared by healthy wild-type (WT) mice whereas mice lacking Muc2 or specific immune regulatory genes demonstrate an impaired ability to combat the pathogen. Here we demonstrate that apical formyl peptide receptor 2 (Fpr2) expression increases in colonic epithelial cells during C. rodentium infection. Using a conventional inoculum dose of C. rodentium, both WT and Fpr2−/− mice were infected and displayed similar signs of disease, although Fpr2−/− mice recovered more slowly than WT mice. However, Fpr2−/− mice exhibited increased susceptibility to C. rodentium colonization in response to low dose infection: 100% of the Fpr2−/− and 30% of the WT mice became colonized and Fpr2−/− mice developed more severe colitis and more C. rodentium were in contact with the colonic epithelial cells. In line with the larger amount of C. rodentium detected in the spleen in Fpr2−/− mice, more C. rodentium and enteropathogenic Escherichia coli translocated across an in vitro mucosal surface to the basolateral compartment following FPR2 inhibitor treatment. Fpr2−/− mice also lacked the striated inner mucus layer that was present in WT mice. Fpr2−/− mice had decreased mucus production and different mucin O-glycosylation in the colon compared to WT mice, which may contribute to their defect inner mucus layer. Thus, Fpr2 contributes to protection against infection and influence mucus production, secretion and organization.

Abbreviations

BSA=

Bovine serum albumin

EDTA=

Ethylenediaminetetaacetic acid

DTT=

Ditiotreitol

TAMRA=

Tetramethylrhodamine

GalNAz=

N-azidoacetylgalactosamine

GlcNAc=

N-acetylglucosamine

NeuAc=

N-acetylneuraminic acid

NeuGc=

N-glycolylneuraminic acid

LC-MS=

Liquid chromatography-mass spectrometry

C. rodentium=

Citrobacter rodentium

E. coli=

Escherichia coli

EPEC=

Enteropathogenic Escherichia coli

EHEC=

Enterohaemorrhagic Escherichia coli

A/E=

Attaching and effacing

CFU=

Colony forming unit

PI=

Post infection

WT=

Wild-type

GI=

Gastrointestinal

DSS=

Dextran-sulfate sodium

FPR=

Formyl peptide receptor

FPR2-/-=

Formyl peptide receptor 2 knock-out

GPCR=

G-protein coupled receptor

IL=

Interleukin

TNF-α=

Tumor necrosis factor alfa

IFN-γ=

Interferon gamma

MCP-1=

Macrophage chemotactic protein-1

MIP=

Macrophage inflammatory protein

H/E=

Hematoxylin/eosin

PAS=

Periodic acid Shiff

LB=

Luria Bertani broth

FBS=

Fetal bovine serum

Disclosure statement

No potential conflict of interest was reported by the authors.

Author Contributions

SS, HF, and SL conceptualized the study. JW and HF provided material/mice. SS, VV, MP, MW, MG, MS performed the experiments. SS and SL wrote the manuscript. All authors critically reviewed the manuscript.

Additional information

Funding

This work was supported by the Swedish Research Council Formas [221-2011-1036 and 221-2013-590], the Swedish Cancer Society, the Ragnar Söderberg, RR Julin, Jeansson and Wilhelm and Martina Lundgrens Scientific Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.