Dual modes of 5-(N-ethyl-N-isopropyl)amiloride modulation of apical dipeptide uptake in the human small intestinal epithelial cell line Caco-2

Kennedy, David J.; Raldúa, Demetrio; Thwaites, David T.

doi:10.1007/s00018-005-5078-3

Cited by 8 publications

(14 citation statements)

References 47 publications

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“…The amiloride analog, EIPA, which inhibits sodium-hydrogen exchange and thereby reduces a driving force for uptake through the apical membrane (H þ electrochemical gradient), 28 been used as a pharmacological inhibitor of macropinocytosis. 24 Previous studies have shown that amiloride and its analogs inhibits pinocytosis of HRP, but not receptor-mediated uptake or uptake via clathrin-coated pits.…”

Section: Discussionmentioning

confidence: 99%

Characterization of antigen and bacterial transport in the follicle-associated epithelium of human ileum

Keita¹,

Gullberg

Ericson

et al. 2006

Laboratory Investigation

100

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The follicle-associated epithelium (FAE), covering Peyer's patches, provides a route of entry for antigens and microorganisms. Animal studies showed enhanced antigen and bacterial uptake in FAE, but no study on barrier function of human FAE has been reported. Our aim was to characterize the normal barrier properties of human FAE. Specimens of normal ileum were taken from 30 patients with noninflammatory colonic disease. Villus epithelium (VE) and FAE were identified and mounted in Ussing chambers. Permeability to 51 Cr-EDTA, transmucosal flux of the protein antigen, horseradish peroxidase (HRP), and transport of fluorescent Escherichia coli (chemically killed K-12 and live HB101) were measured. Uptake mechanisms were studied by confocal-and transmission electron microscopy, and by using pharmacological inhibitors in an in vitro coculture model of FAE and in human ileal FAE. HRP flux was substantially higher in FAE than in VE, and was reduced by an amiloride analog. Electron microscopy showed HRP-containing endosomes. Transport of E. coli K-12 and HB101 was also augmented in FAE and was confirmed by confocal microscopy. In vitro coculture experiments and electron microscopy revealed actin-dependent, mainly transcellular, uptake of E. coli K-12 into FAE. 51 Cr-EDTA permeability was equal in FAE and VE. Augmented HRP flux and bacterial uptake but similar paracellular permeability, suggest functional variations of transcellular transport in the FAE. We show for the first time that FAE of human ileum is functionally distinct from regular VE, rendering the FAE more prone to bacterial-epithelial cell interactions and delivery of antigens to the mucosal immune system.

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Section: Discussionmentioning

confidence: 99%

Characterization of antigen and bacterial transport in the follicle-associated epithelium of human ileum

Keita¹,

Gullberg

Ericson

et al. 2006

Laboratory Investigation

100

View full text Add to dashboard Cite

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“…It is H ϩ coupled, being stimulated by a transapical membrane H ϩ gradient (usually outside acidic corresponding to the luminal acid microclimate, although luminal acidity is not necessary), but is Na ϩ independent. This H ϩ gradient normally depends on BB NHE activity in small intestine and Caco-2 cells, requires extracellular Na ϩ , is inhibited by a specific NHE3 inhibitor (S1611) and by elevating cAMP (which also inhibits NHE3), and is calmodulin dependent (19,57,148,239,240,337,446,447,485). Increase of Gly-Sar uptake via PEPT1 was proportional to NHE3 expression in a transfection system, showing NHE3 can drive PEPT1 function (485).…”

Section: Functional Interactions Of Nhe3 With Proteins Not Known mentioning

confidence: 98%

Regulatory Binding Partners and Complexes of NHE3

Donowitz

Li²

2007

Physiological Reviews

178

189

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NHE3 is the brush-border (BB) Na(+)/H(+) exchanger of small intestine, colon, and renal proximal tubule which is involved in large amounts of neutral Na(+) absorption. NHE3 is a highly regulated transporter, being both stimulated and inhibited by signaling that mimics the postprandial state. It also undergoes downregulation in diarrheal diseases as well as changes in renal disorders. For this regulation, NHE3 exists in large, multiprotein complexes in which it associates with at least nine other proteins. This review deals with short-term regulation of NHE3 and the identity and function of its recognized interacting partners and the multiprotein complexes in which NHE3 functions.

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“…Using Caco-2 cells, loaded with a pH-sensitive dye, it was demonstrated that PEPT1 in intestinal epithelial cells has an acid-loading activity and that the apical Na + /H + exchanger activity is required for the recovery from the acid load [25]. Studies using selective NHE3 inhibitors also illustrated the importance of NHE3 transport for PEPT1-mediated H + -dipeptide cotransport [25][26][27][28][29]. Any maneuvers which alter the pH and subsequently change the membrane potential can therefore also result in changes in the uptake of substrates by PEPT1 [29,30].…”

Section: Mode Of Transportmentioning

confidence: 99%

Amino acid absorption and homeostasis in mice lacking the intestinal peptide transporter PEPT1

Näßl

Rubio‐Aliaga

Fenselau

et al. 2011

American Journal of Physiology-Gastrointestinal and Liver Physi

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The intestinal peptide transporter PEPT1 mediates the uptake of di- and tripeptides derived from dietary protein breakdown into epithelial cells. Whereas the transporter appears to be essential to compensate for the reduced amino acid delivery in patients with mutations in amino acid transporter genes, such as in cystinuria or Hartnup disease, its physiological role in overall amino acid absorption is still not known. To assess the quantitative importance of PEPT1 in overall amino acid absorption and metabolism, PEPT1-deficient mice were studied by using brush border membrane vesicles, everted gut sacs, and Ussing chambers, as well as by transcriptome and proteome analysis of intestinal tissue samples. Neither gene expression nor proteome profiling nor functional analysis revealed evidence for any compensatory changes in the levels and/or function of transporters for free amino acids in the intestine. However, most plasma amino acid levels were increased in Pept1(-/-) compared with Pept1(+/+) animals, suggesting that amino acid handling is altered. Plasma appearance rates of (15)N-labeled amino acids determined after intragastric administration of a low dose of protein remained unchanged, whereas administration of a large protein load via gavage revealed marked differences in plasma appearance of selected amino acids. PEPT1 seems, therefore, important for overall amino acid absorption only after high dietary protein intake when amino acid transport processes are saturated and PEPT1 can provide additional absorption capacity. Since renal amino acid excretion remained unchanged, elevated basal concentrations of plasma amino acids in PEPT1-deficient animals seem to arise mainly from alterations in hepatic amino acid metabolism.

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Dual modes of 5-(N-ethyl-N-isopropyl)amiloride modulation of apical dipeptide uptake in the human small intestinal epithelial cell line Caco-2

Cited by 8 publications

References 47 publications

Characterization of antigen and bacterial transport in the follicle-associated epithelium of human ileum

Characterization of antigen and bacterial transport in the follicle-associated epithelium of human ileum

Regulatory Binding Partners and Complexes of NHE3

Amino acid absorption and homeostasis in mice lacking the intestinal peptide transporter PEPT1

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