Lactobacillus acidophilus counteracts inhibition of NHE3 and DRA expression and alleviates diarrheal phenotype in mice infected with Citrobacter rodentium.

Impaired absorption of electrolytes is a hallmark of diarrhea associated with inflammation or enteric infections. Intestinal epithelial luminal membrane NHE3 (Na+/H+ exchanger 3) and DRA (Down-Regulated in Adenoma; Cl-/HCO3- exchanger) play key roles in mediating electroneutral NaCl absorption. We have previously shown decreased NHE3 and DRA function in response to short-term infection with enteropathogenic E coli (EPEC), a diarrheal pathogen. Recent studies have also shown substantial downregulation of DRA expression in a diarrheal model of infection with Citrobacter rodentium, the mouse counterpart of EPEC. Since our previous studies showed that the probiotic Lactobacillus acidophilus (LA) increased DRA and NHE3 function and expression and conferred protective effects in experimental colitis, we sought to evaluate the efficacy of LA in counteracting NHE3 and DRA inhibition and ameliorating diarrhea in a model of C rodentium infection. FVB/N mice challenged with C rodentium [1 × 109 colony-forming units (CFU)] with or without administration of live LA (3 × 109 CFU) were assessed for NHE3 and DRA mRNA and protein expression, mRNA levels of carbonic anhydrase, diarrheal phenotype (assessed by colonic weight-to-length ratio), myeloperoxidase activity, and proinflammatory cytokines. LA counteracted C rodentium-induced inhibition of colonic DRA, NHE3, and carbonic anhydrase I and IV expression and attenuated diarrheal phenotype and MPO activity. Furthermore, LA completely blocked C rodentium induction of IL-1β, IFN-γ, and CXCL1 mRNA and C rodentium-induced STAT3 phosphorylation. In conclusion, our data provide mechanistic insights into antidiarrheal effects of LA in a model of infectious diarrhea and colitis.