Toxin-mediated downregulation of absorptive ion transporters NHE3, DRA, and SGLT1 in the colon contributes to diarrhea associated with Clostridioides difficile infection.

Background & AimClostridioides difficile infection (CDI) is the leading cause of hospital-acquired diarrhea and pseudomembranous colitis. Two protein toxins, TcdA and TcdB, produced by C. difficile are the major determinants of disease. However, the physiological cause of diarrhea associated with CDI is not well understood. We investigated the effects of CDI on paracellular permeability and apical ion transporters. MethodsWe studied intestinal permeability and apical membrane transporters in female C57BL/6J mice. Ussing chambers were used to measure regional differences in paracellular permeability and ion transporter function in intestinal mucosa. Intestinal tissues were collected from mice and analyzed by immunofluorescence microscopy and RNA-sequencing. ResultsCDI increased intestinal permeability through the size-selective leak pathway in vivo, but permeability was not increased at the sites of pathological damage. Chloride secretion was reduced in the cecum during infection by decreased CaCC function. Infected mice had decreased SGLT1 (also called SLC5A1) activity in the cecum and colon along with diminished apical abundance and an increase in luminal glucose. SGLT1 and DRA (also called SLC26A3) expression was ablated by either TcdA or TcdB, but NHE3 (also called SLC9A3) was decreased in a TcdB-dependent manner. Finally, expression of these three ion transporters was drastically reduced at the transcriptional level. ConclusionsCDI increases intestinal permeability and decreases apical abundance of NHE3, SGLT1, and DRA. This combination may cause a dysfunction in water and solute absorption in the lower gastrointestinal tract, leading to osmotic diarrhea. These findings may open novel pathways for attenuating CDI-associated diarrhea. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=185 HEIGHT=200 SRC="FIGDIR/small/516162v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@e6e23corg.highwire.dtl.DTLVardef@ed6bborg.highwire.dtl.DTLVardef@33adcaorg.highwire.dtl.DTLVardef@d6e359_HPS_FORMAT_FIGEXP M_FIG C_FIG