Abstract
A mucus layer coats the gastrointestinal tract and serves as the first line of intestinal defense against infection. N-acyl-homoserine lactone (AHL) quorum-sensing molecules produced by gram-negative bacteria in the gut can influence the homeostasis of intestinal epithelium. In this study, we investigated the effects of two representative long- and short-chain AHLs, N-3-(oxododecanoyl)-homoserine lactone (C12-HSL) and N-butyryl homoserine lactone (C4-HSL), on cell viability and mucus secretion in LS174T cells. C12-HSL but not C4-HSL significantly decreased cell viability by inducing mitochondrial dysfunction and activating cell apoptosis which led to a decrease in mucin expression. Pretreatment with lipid raft disruptor (Methyl-β-cyclodextrin, MβCD) and oxidative stress inhibitor (N-acetyl-L-cysteine, NAC) slightly rescued the viability of cells damaged by C12-HSL exposure, while the paraoxonase 2 (PON2) inhibitor (Triazolo[4,3-a]quinolone, TQ416) significantly affected recovering cells viability and mucin secretion. When LS174T cells were treated with C12-HSL and TQ416 simultaneously, TQ416 showed the maximal positive effect on cells viability. However, if cells were first treated with C12-HSL for 40 mins, and then TQ46 was added, the TQ416 had no effect on cell viability. These results suggest that the C12-HSL-acid process acts at an early step to activate apoptosis as part of C12-HSL’s effect on intestinal mucus barrier function.
Highlights
The gut epithelium is coated with a thick mucus layer that functions as the first-line defensive barrier against invading microbes and pathogenic antigens[1,2]
To investigate the effect of acylhomoserine lactone (AHL) on the survival of human intestinal secretory cells and whether this effect is dependent on the length of the carbon chain of AHL, LS174T cells were treated with a long-carbon-chain AHL, C12HSL, or a short-carbon-chain AHL, C4-HSL, at various concentrations, ranging from 0 to 200 μM, for 4 h
To determine whether the survival inhibition of LS174T cells by C12-HSL was due to the induction of apoptosis, C12-HSL-treated LS174T cells were dual-stained with Annexin V and propidium iodide (PI) and analyzed by flow cytometry
Summary
The gut epithelium is coated with a thick mucus layer that functions as the first-line defensive barrier against invading microbes and pathogenic antigens[1,2]. As QS molecules, N-acylhomoserine lactone (AHL) that is produced by gram-negative bacteria in the gut can influence homeostasis of the host intestinal epithelium. This can perturb epithelial integrity and the development of intestinal diseases[29]. Our results indicate that PON2 is a major component mediating C12-HSL-induced apoptotic effects on LS174T cells These findings will guide our understanding of the underlying causes of intestinal mucus barrier disorder in Pseudomonas aeruginosa (Pa) infection patients, and may suggest novel therapeutic targets exploited to limit the pathogenicity of Pa
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