title: Altered expression and localization of ion transporters contribute to diarrhea in mice with Salmonella-induced enteritis.
abstract: OBJECTIVE
  Salmonella enterica serovar Typhimurium is an enteropathogen that causes self-limiting diarrhea in healthy individuals, but poses a significant health threat to vulnerable populations. Our understanding of the pathogenesis of Salmonella-induced diarrhea has been hampered by the lack of a suitable mouse model. After a dose of oral kanamycin, Salmonella-infected congenic BALB/c.D2(NrampG169) mice, which carry a wild-type Nramp1 gene, develop clear manifestations of diarrhea. We used this model to elucidate the pathophysiology of Salmonella-induced diarrhea.
  
  
  METHODS
  BALB /c.D2(NrampG169) mice were treated with kanamycin and then infected with wild-type or mutant Salmonella by oral gavage. Colon tissues were isolated and Ussing chambers, quantitative polymerase chain reaction, immunoblot, and confocal microscopy analyses were used to study function and expression of ion transporters and cell proliferation.
  
  
  RESULTS
  Studies with Ussing chambers demonstrated reduced basal and/or adenosine 3',5'-cyclic monophosphate-mediated electrogenic ion transport in infected colonic tissues, attributable to changes in chloride or sodium transport, depending on the segment studied. The effects of infection were mediated, at least in part, by effector proteins secreted by the bacterial Salmonella pathogenicity island 1- and Salmonella pathogenicity island-2-encoded virulence systems. Infected tissue showed reduced expression of the chloride-bicarbonate exchanger down-regulated in adenoma in surface colonic epithelial cells. Cystic fibrosis transmembrane conductance regulator was internalized in colonic crypt epithelial cells without a change in overall expression levels. Confocal analyses, densitometry, and quantitative polymerase chain reaction revealed that expression of epithelial sodium channel β was reduced in distal colons of Salmonella-infected mice. The changes in transporter expression, localization, and/or function were accompanied by crypt hyperplasia in Salmonella-infected mice.
  
  
  CONCLUSIONS
  Salmonella infection induces diarrhea by altering expression and/or function of transporters that mediate water absorption in the colon, likely reflecting the fact that epithelial cells have less time to differentiate into surface cells when proliferation rates are increased by infection.
authors.affiliation: Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California.
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Marchelletta
authors.forename: Melanie G
authors.initials: MG
authors.lastname: Gareau
authors.forename: Declan F
authors.initials: DF
authors.lastname: McCole
authors.forename: Sharon
authors.initials: S
authors.lastname: Okamoto
authors.forename: Elise
authors.initials: E
authors.lastname: Roel
authors.forename: Rachel
authors.initials: R
authors.lastname: Klinkenberg
authors.forename: Donald G
authors.initials: DG
authors.lastname: Guiney
authors.forename: Joshua
authors.initials: J
authors.lastname: Fierer
authors.forename: Kim E
authors.initials: KE
authors.lastname: Barrett
mesh_terms: D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D003106:Colon / Q000382:microbiology / Q000473:pathology / Q000503:physiopathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology*; D003967:Diarrhea / Q000503:physiopathology*; D004195:Disease Models, Animal; D004751:Enteritis / Q000382:microbiology / Q000503:physiopathology*; D053503:Epithelial Sodium Channels / Q000502:physiology*; D005260:Female; D006965:Hyperplasia; D007413:Intestinal Mucosa / Q000382:microbiology / Q000473:pathology / Q000503:physiopathology; D017136:Ion Transport / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D012486:Salmonella typhimurium / Q000472:pathogenicity*; D000099173:Natural Resistance-associated Macrophage Protein 1
chemical_list: D027682:Cation Transport Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D053503:Epithelial Sodium Channels; D000099173:Natural Resistance-associated Macrophage Protein 1
keywords: CFTR; Colon; DRA; ENaC; FSK; Kana; SPI; Salmonella; Salmonella pathogenicity island; T3SS; cystic fibrosis transmembrane conductance regulator; down-regulated in adenoma; epithelial sodium channel; forskolin; kanamycin; mRNA; messenger RNA; qPCR; quantitative polymerase chain reaction; type-3 protein secretion system; wild-type; wt