Listeriolysin O Affects the Permeability of Caco-2 Monolayer in a Pore-Dependent and Ca2+-Independent Manner.

Miša Mojca Cajnko,Simon Caserman,Gregor Anderluh,Matic Kisovec,Maja Marušić,Nejc Rojko,Mojca Benčina,Daniel Gillet

doi:10.1371/journal.pone.0130471

Miša Mojca Cajnko, Simon Caserman + Show 6 more

Open Access

https://doi.org/10.1371/journal.pone.0130471

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Journal: PloS one	Publication Date: Jun 18, 2015
Citations: 22	License type: CC BY 4.0

Affiliation: National Institute of Chemistry, University of Ljubljana

Abstract

Listeria monocytogenes is a food and soil-borne pathogen that secretes a pore-forming toxin listeriolysin O (LLO) as its major virulence factor. We tested the effects of LLO on an intestinal epithelial cell line Caco-2 and compared them to an unrelated pore-forming toxin equinatoxin II (EqtII). Results showed that apical application of both toxins causes a significant drop in transepithelial electrical resistance (TEER), with higher LLO concentrations or prolonged exposure time needed to achieve the same magnitude of response than with EqtII. The drop in TEER was due to pore formation and coincided with rearrangement of claudin-1 within tight junctions and associated actin cytoskeleton; however, no significant increase in permeability to fluorescein or 3 kDa FITC-dextran was observed. Influx of calcium after pore formation affected the magnitude of the drop in TEER. Both toxins exhibit similar effects on epithelium morphology and physiology. Importantly, LLO action upon the membrane is much slower and results in compromised epithelium on a longer time scale at lower concentrations than EqtII. This could favor listerial invasion in hosts resistant to E-cadherin related infection.

Highlights

Listeria monocytogenes is an invasive Gram-positive enteric pathogen
In our current study we aimed to examine the effects of listeriolysin O (LLO) pore-formation on the intestinal epithelium model cell line Caco-2 and compare them to effects of another non-related poreforming toxin equinatoxin II (EqtII)
Apical application of 125 nM LLO caused a 60% drop in transepithelial electrical resistance (TEER) after 3 minutes, whereas 100 nM EqtII resulted in a drop of more than 80% of initial value

Summary

Introduction

Listeria monocytogenes is an invasive Gram-positive enteric pathogen. It can cause life-threatening diseases like septicemia, meningitis, meningoencephalitis, and severe gastroenteritis [1]. The bacterium expresses multiple virulence factors that help its entry and survival in host cells [2,3,4]. One of its major virulence factors is a pore-forming toxin listeriolysin O (LLO) [5]. LLO belongs to a family of cholesterol-dependent cytolysins (CDCs), pore-forming toxins produced by many Gram-positive bacteria [6]. CDCs are 50–70 kDa proteins that bind to cholesterol in host cell membranes and form large pores comprised of 35–50 monomers with a diameter of 25–40 nm [7]. To invade non-phagocytic cells at least two listerial surface proteins are usually

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