Characterisation of Early Mucosal and Neuronal Lesions Following Shigella flexneri Infection in Human Colon

Emmanuel Coron,Philippe J Sansonetti,Michel Neunlist,Thilo Wedel,Philippe Aubert,Jean P Galmiche,Mathurin Flamant,Thierry Pedron,Eric Letessier

doi:10.1371/journal.pone.0004713

Abstract

Background Shigella, an enteroinvasive bacteria induces a major inflammatory response responsible for acute rectocolitis in humans. However, early effect of Shigella flexneri (S. flexneri) infection upon the human mucosa and its microenvironement, in particular the enteric nervous system, remains currently unknown. Therefore, in this study, we sought to characterize ex vivo the early events of shigellosis in a model of human colonic explants. In particular, we aimed at identifying factors produced by S. flexneri and responsible for the lesions of the barrier. We also aimed at determining the putative lesions of the enteric nervous system induced by S. flexneri.Methodology/Principal FindingsWe first showed that, following 3 h of infection, the invasive but not the non-invasive strain of S. flexneri induced significant desquamation of the intestinal epithelial barrier and a reduction of epithelial height. These changes were significantly reduced following infection with SepA deficient S. flexneri strains. Secondly, S. flexneri induced rapid neuronal morphological alterations suggestive of cell death in enteric submucosal neurones. These alterations were associated with a significant increase in the proportion of vasoactive intestinal peptide (VIP) immunoreactive (IR) neurons but not in total VIP levels. The NMDA receptor antagonist MK-801 blocked neuronal morphological changes induced by S. flexneri, but not the increase in the proportion of VIP-IR.Conclusions/SignificanceThis human explant model can be used to gain better insight into the early pathogenic events following S. flexneri infection and the mechanisms involved.

Highlights

Diarrheal diseases induced by bacterial, viral or parasitic pathogens represent a major world-wide public health problem
Using an ex vivo human organ culture model, we showed that the invasive but not the non invasive strain of S. flexneri induced significant desquamation of the intestinal epithelial barrier (IEB) which was significantly reduced following infection with SepA deficient S. flexneri strains
Morphological changes induced by S. flexneri but not the increase in vasoactive intestinal peptide (VIP)-IR were blocked by the NMDA receptor antagonist MK-801

Summary

Introduction

Diarrheal diseases induced by bacterial, viral or parasitic pathogens represent a major world-wide public health problem. S. flexneri triggers an acute inflammation in part due 1) to apoptosis of monocytes and macrophages, which widely release pro-inflammatory cytokines and 2) to the stimulation of the innate immune response via the activation of Nod- and Toll-like receptors by bacterial cell components [6]. This inflammation facilitates the intestinal barrier rupture and bacterial spread within intestinal epithelial cells at a distance from the initial entry site, further amplifying the inflammatory response and mucosal damage [6]. We aimed at determining the putative lesions of the enteric nervous system induced by S. flexneri

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