Chloride-led Disruption of the Intestinal Mucous Layer Impedes <i>Salmonella</i> Invasion: Evidence for an ‘Enteric Tear’ Mechanism

Abstract

Background/Aims: Methods: The intestinal epithelial layer can switch from a net absorptive state to one of net secretion in the presence of luminal toxins and pathogens. This suggests an innate defence role for regulated secretion of mucus, electrolytes and water. We hypothesised that chloride-led fluid secretion across the mucus-covered intestinal epithelium alters barrier properties by influencing the overlying mucous-gel layer. Results: We demonstrated that chloride-led disruption of the epithelial-associated mucus-gel covering HT29-MTX-E12 (E12) human colonic epithelial monolayers, a goblet-cell like line derived from parental HT29 cells, resulted in reduction of associated mucus as well as a reduction in mucous-gel density and barrier properties. Changes in epithelial secretory state were accompanied by increased water transport, and the resulting loss of gel integrity reduced Salmonella typhimuriuminvasion of epithelia in both E12 monolayers and of isolated rat ileal mucosae. However, neither chloride secretion nor mucus disruption altered numbers of adhering bacteria. Conclusion: These data suggest a role for chloride led fluid secretion in the shedding of the adherent mucous-gel layer, possibly as a rate-limiting innate defence mechanism, and offer evidence for “enteric tears” in intestinal host defence.

Contribution of epithelial innate immunity to systemic protection afforded by prolyl hydroxylase inhibition in murine colitis

“…FD-4 concentration was calculated from fluorescent standard curves (Spectramax m5e, Molecular Devices, USA). The velocity of FD-4 across the intestinal barrier; the apparent permeability (P app ) for FD-4, was calculated from the following equation: $$P_{\mathit{app}}false(cm/sfalse)=false(dQ/dtfalse)/false(A·Cofalse),$$ where dQ/dt is the transport rate (mol/s of FD-4), A is the surface area of the monolayer or sac (cm 2 ), and Co is the initial concentration in the donor compartment (mol/mL) 42, 44, 45 .…”

Canonical and noncanonical inflammasomes in intestinal epithelial cells

“…Studies have implicated a role for NLRP6 in regulating mucus secretion from goblet cells. Nlrp6 −/− mice display altered mucus secretion and increased colonisation of Citrobacter rodentium (Wlodarska et al, ), indicating an inability to clear pathogens (Keely et al, ). In a separate study, goblet cell secretion of MUC2, the main mucin in the intestine, was shown to be NLRP6‐dependent (Birchenough, Nyström, Johansson, & Hansson, ).…”

“…Studies have implicated a role for NLRP6 in regulating mucus secretion from goblet cells. Nlrp6 −/− mice display altered mucus secretion and increased colonisation of Citrobacter rodentium (Wlodarska et al, 2014), indicating an inability to clear pathogens (Keely et al, 2011).…”

Pathogenesis of Human Enterovirulent Bacteria: Lessons from Cultured, Fully Differentiated Human Colon Cancer Cell Lines

“…Chloride secretion induced in fully differentiated, mucin-secreting HT29-MTX cells results in the shedding of the mucus gel covering the apical cell domain and a reduction in mucus gel density and barrier properties, which in turn limits the innate defense mechanism against S. Typhimurium invasion (749).…”