LAUSR

ABSTRACT The intestine is home to the largest microbiota community of the human body and strictly regulates its barrier function. Tight junctions (TJ) are major actors of the intestinal barrier, which is impaired in inflammatory bowel disease (IBD), along with an unbalanced microbiota composition. With the aim to identify new actors involved in host-microbiota interplay in IBD, we studied N-acyl homoserine lactones (AHL), molecules of the bacterial quorum sensing, which also impact the host. We previously identified in the gut a new and prominent AHL, 3-oxo-C12:2, which is lost in IBD. We investigated how 3-oxo-C12:2 impacts the intestinal barrier function, in comparison to 3-oxo-C12, a structurally close AHL produced by the opportunistic pathogen P. aeruginosa. Using Caco-2/TC7 cells as a model of polarized enterocytes, we compared the effects on paracellular permeability and TJ integrity of these two AHL, separately or combined with pro-inflammatory cytokines, Interferon-γ and Tumor Necrosis Factor-α, known to disrupt the barrier function during IBD. While 3-oxo-C12 increased paracellular permeability and decreased occludin and tricellulin signal at bicellular and tricellular TJ, respectively, 3-oxo-C12:2 modified neither permeability nor TJ integrity. Whereas 3-oxo-C12 potentiated the hyperpermeability induced by cytokines, 3-oxo-C12:2 attenuated their deleterious effects on occludin and tricellulin, and maintained their interaction with their partner ZO-1. In addition, 3-oxo-C12:2 limited the cytokine-induced ubiquitination of occludin and tricellulin, suggesting that this AHL prevented their endocytosis. In conclusion, the role of 3-oxo-C12:2 in maintaining TJ integrity under inflammatory conditions identifies this new AHL as a potential beneficial actor of host–microbiota interactions in IBD.