Pathogenic Escherichia coli increase Cl– secretion from intestinal epithelia by upregulating galanin-1 receptor expression
Gail Hecht, … , Athanasia Koutsouris, Richard V. Benya
Gail Hecht, … , Athanasia Koutsouris, Richard V. Benya
Published August 1, 1999
Citation Information: J Clin Invest. 1999;104(3):253-262. https://doi.org/10.1172/JCI6373.
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Article

Pathogenic Escherichia coli increase Cl– secretion from intestinal epithelia by upregulating galanin-1 receptor expression

Abstract

Galanin is widely distributed in enteric nerve terminals lining the human gastrointestinal (GI) tract. We have shown previously that galanin-1 receptors (Gal1-R) are expressed by epithelial cells lining the human GI tract, and upon activation cause Cl– secretion. Because expression of this receptor is transcriptionally regulated by nuclear factor-κB (NF-κB), which is activated by enteric pathogens as a part of the host epithelial response to infection, we investigated whether such bacterial pathogens could directly increase Gal1-R expression in the T84-cell model system. Pathogenic Escherichia coli, but not nonpathogenic E. coli, activate a p50/p65 NF-κB complex that binds to oligonucleotides corresponding to a recognition site located within the 5′ flanking region of the human GAL1R gene. Pathogenic E. coli, but not normal commensal organisms, increase Gal1-R mRNA synthesis and [125I]galanin binding sites. Whereas galanin increases short-circuit current (Isc) approximately 5-fold in uninfected T84 cells, exposure to pathogenic, but not nonpathogenic, E. coli results in galanin increasing Isc approximately 20-fold. To confirm the validity of these in vitro observations, we also studied C57BL/6J mice infected with enterohemorrhagic E. coli (EHEC) by gavage. Infection caused a progressive increase in both NF-κB activation and Gal1-R expression, with maximal levels of both observed 3 days after gavage. Ussing chamber studies revealed that colons infected with EHEC, but not those exposed to normal colonic flora, markedly increased Isc in response to galanin. These data indicate that pathogen-induced increases in Gal1-R expression by epithelial cells lining the colon may represent a novel unifying pathway responsible for at least a portion of the excessive fluid secretion observed during infectious diarrhea.

Authors

Gail Hecht, Jorge A. Marrero, Alexey Danilkovich, Kristina A. Matkowskyj, Suzanna D. Savkovic, Athanasia Koutsouris, Richard V. Benya

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Effect of NF-κB inhibitors on Gal1-R mRNA synthesis and response to gala...
Effect of NF-κB inhibitors on Gal1-R mRNA synthesis and response to galanin after infection with pathogenic E. coli. (a) Dose-dependent effect of the NF-κB–specific inhibitor CAPE (25) on peak Gal1-R mRNA synthesis 4 hours after a 1-hour exposure to EHEC. Confluent T84 cells were exposed to the indicated concentration of CAPE for 1 hour, infected with EHEC for 1 hour in the continued presence of CAPE, and washed; RNA was extracted 4 hours later. (b) Dose-dependent effect of dexamethasone on Gal1-R mRNA synthesis 4 hours after a 1-hour exposure to EHEC. Conditions were identical to those described for a. (c) Effects of dexamethasone on galanin-induced Isc after infection with EHEC. T84 cells were infected with EHEC for 1 hour in the presence or absence of 200 nM dexamethasone, and the Isc response to 1 μM galanin was determined 24 hours later. Data represent the mean ± SEM for a minimum of 3 separate experiments.