Escherichia coli heat-stable enterotoxin mediates Na+/H+ exchanger 4 inhibition involving cAMP in T-84 human intestinal epithelial cells

Beltran, Ana R., Carraro-Lacroix, Luciene R., Bezerra, Camila N. A., Cornejo, Marcelo, Norambuena, Katrina, Toledo, Fernando, Araos, Joaquin, Pardo, Fabian, Leiva, Andrea, Sanhueza, Carlos, Malnic, Gerhard, Sobrevia, Luis and Ramirez, Marco A. (2015) Escherichia coli heat-stable enterotoxin mediates Na+/H+ exchanger 4 inhibition involving cAMP in T-84 human intestinal epithelial cells. PloS One, 10 12: . doi:10.1371/journal.pone.0146042


Author Beltran, Ana R.
Carraro-Lacroix, Luciene R.
Bezerra, Camila N. A.
Cornejo, Marcelo
Norambuena, Katrina
Toledo, Fernando
Araos, Joaquin
Pardo, Fabian
Leiva, Andrea
Sanhueza, Carlos
Malnic, Gerhard
Sobrevia, Luis
Ramirez, Marco A.
Title Escherichia coli heat-stable enterotoxin mediates Na+/H+ exchanger 4 inhibition involving cAMP in T-84 human intestinal epithelial cells
Formatted title
Escherichia coli heat-stable enterotoxin mediates Na+/H+ exchanger 4 inhibition involving cAMP in T-84 human intestinal epithelial cells
Journal name PloS One   Check publisher's open access policy
ISSN 1932-6203
Publication date 2015-12-29
Sub-type Article (original research)
DOI 10.1371/journal.pone.0146042
Open Access Status DOI
Volume 10
Issue 12
Total pages 15
Place of publication San Francisco, United States
Publisher Public Library of Science
Language eng
Formatted abstract
The enterotoxigenic Escherichia coli strains lead to diarrhoea in humans due to heat-labile and heat-stable (STa) enterotoxins. STa increases Cl-release in intestinal cells, including the human colonic carcinoma T84 cell line, involving increased cGMP and membrane alkalization due to reduced Na+/H+ exchangers (NHEs) activity. Since NHEs modulate intracellular pH (pHi), and NHE1, NHE2, and NHE4 are expressed in T84 cells, we characterized the STa role as modulator of these exchangers. pHi was assayed by the NH4Cl pulse technique and measured by fluorescence microscopy in BCECF–preloaded cells. pHi recovery rate (dpHi/dt) was determined in the absence or presence of 0.25 μmol/L STa (30 minutes), 25 μmol/L HOE-694 (concentration inhibiting NHE1 and NHE2), 500 μmol/L sodium nitroprusside (SNP, spontaneous nitric oxide donor), 100 μmol/L dibutyryl cyclic GMP (db-cGMP), 100 nmol/L H89 (protein kinase A inhibitor), or 10 μmol/L forskolin (adenylyl cyclase activator). cGMP and cAMP were measured in cell extracts by radioimmunoassay, and buffering capacity (ßi) and H+ efflux (JH+) was determined. NHE4 protein abundance was determined by western blotting. STa and HOE-694 caused comparable reduction in dpHi/dt and JH+ (~63%), without altering basal pHi (range 7.144–7.172). STa did not alter ßi value in a range of 1.6 pHi units. The dpHi/dt and JH+ was almost abolished (~94% inhibition) by STa + HOE-694. STa effect was unaltered by db-cGMP or SNP. However, STa and forskolin increased cAMP level. STa–decreased dpHi/dt and JH+ was mimicked by forskolin, and STa + HOE-694 effect was abolished by H89. Thus, incubation of T84 cells with STa results in reduced NHE4 activity leading to a lower capacity of pHi recovery requiring cAMP, but not cGMP. STa effect results in a causal phenomenon (STa/increased cAMP/increased PKA activity/reduced NHE4 activity) ending with intracellular acidification that could have consequences in the gastrointestinal cells function promoting human diarrhoea.
Keyword T84 cells
Fluid secretion
Cl-secretion
Diarrhea
Rat
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Article # e0146042

Document type: Journal Article
Sub-type: Article (original research)
Collections: UQ Centre for Clinical Research Publications
Faculty of Medicine
Official 2016 Collection
 
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