Slug and Snail have differential effects in directing colonic epithelial wound healing and partially mediate the restitutive effects of butyrate

Restitution of wounds in colonic epithelium is essential in the maintenance of health. Microbial products, such as the short-chain fatty acid butyrate, can have positive effects on wound healing. We used an in vitro model of T84 colonic epithelial cells to determine if the Snail genes Slug ( SNAI2) and Snail ( SNAI1), implemented in keratinocyte monolayer healing, are involved in butyrate-enhanced colonic epithelial wound healing. Using shRNA-mediated Slug/Snail knockdown, we found that knockdown of Slug (Slug-KD), but not Snail (Snail-KD), impairs wound healing in scratch assays with and without butyrate. Slug and Snail had differential effects on T84 monolayer barrier integrity, measured by transepithelial resistance, as Snail-KD impaired the barrier (with or without butyrate), whereas Slug-KD enhanced the barrier, again with or without butyrate. Targeted transcriptional analysis demonstrated differential expression of several tight junction genes, as well as focal adhesion genes. This included altered regulation of Annexin A2 and ITGB1 in Slug-KD, which was reflected in confocal microscopy, showing increased accumulation of B1-integrin protein in Slug-KD cells, which was previously shown to impair wound healing. Transcriptional analysis also indicated altered expression of genes associated with epithelial terminal differentiation, such that Slug-KD cells skewed toward overexpression of secretory cell pathway-associated genes. This included trefoil factors TFF1 and TFF3, which were expressed at lower than control levels in Snail-KD cells. Since TFFs can enhance the barrier in epithelial cells, this points to a potential mechanism of differential modulation by Snail genes. Although Snail genes are crucial in epithelial wound restitution, butyrate responses are mediated by other pathways as well.NEW &amp; NOTEWORTHY Although butyrate can promote colonic mucosal healing, not all of its downstream pathways are understood. We show that the Snail genes Snail and Slug are mediators of butyrate responses. Furthermore, these genes, and Slug in particular, are necessary for efficient restitution of wounds and barriers in T84 epithelial cells even in the absence of butyrate. These effects are achieved in part through effects on regulation of β1 integrin and cellular differentiation state.</jats:p

Discovery of a protective, transmissible, and type 2 inflammation-skewing intestinal microbiome

Abstract We recently discovered a transmissible, dominant, and remarkably protective intestinal microbiome (a “Magical Microbiome,” MM) in the setting of a murine model of colitis. The objective of this project is to fill current knowledge gaps regarding the molecular mechanisms underlying protection in this novel model of microbiome-mediated protection. Protection can be transmitted to unmanipulated conventional or germ-free C57Bl/6 mice via cohousing or oral gavage of MM+ stool. During DSS-induced colitis, MM+ mice develop less weight loss, intestinal pathology, and production of proinflammatory molecules relative to genetically identical C57Bl/6 MM-controls. Preliminary results suggest that the eukaryotic and bacterial microbiome under investigation re-programs the host inflammation to prevent disease or promote repair. MM-mediated protection is IL-13-dependent and associated with enhanced type 2 inflammation, as transcript levels of type 2-associated genes including IL-4, IL-13, and Fizz1 were significantly higher in colons of MM+ mice. 16s rRNA gene sequencing and eukaryote screening demonstrated that MM+ mice have a bacterial microbiome distinct from controls and host a novel Tritrichomonas species. Transfer of Tritrichomonas to wild-type mice correlated with protection, but vancomycin treatment ameliorates the protection while maintaining Tritrichomonas, suggesting a possible interaction between bacteria and protist. Stool metabolites are also distinct between MM+ and MM− hosts, further supporting a distinct microbiome function. Overall, we possess a unique microbiome that can be used to understand protective host-microbe interactions and identify novel therapeutic targets for inflammatory diseases.</jats:p