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. 1998 Feb;42(2):200–207. doi: 10.1136/gut.42.2.200

Rapid modulation of electrolyte transport in Caco-2 cell monolayers by enteropathogenic Escherichia coli (EPEC) infection

G Collington 1, I Booth 1, S Knutton 1
PMCID: PMC1726999  PMID: 9536944

Abstract

Background and aims—The pathophysiology of enteropathogenic Escherichia coli (EPEC) diarrhoea remains uncertain. EPEC adhere to enterocytes and transduce signals which produce a characteristic "attaching and effacing" (A/E) lesion in the brush border membrane. The present in vitro study was designed to determine whether signal transduction by EPEC also influences electrolyte transport. 
Methods—Caco-2 cell monolayers were rapidly infected with wild type EPEC strain E2348/69, or the signal transduction-defective mutant 14.2.1(1), and mounted in Ussing chambers. 
Results—Strain E2348/69 stimulated a rapid but transient increase in short circuit current (Isc) which coincided with A/E lesion formation; this Isc response was absent on infection with strain 14.2.1(1). While the initial rise in Isc induced by E2348/69 was partially (~35%) dependent on chloride, the remainder possibly represents an influx of sodium and amino acid(s) across the apical membrane. 
Conclusions—The study directly shows that, after initial adhesion, EPEC induce major alterations in host cell electrolyte transport. The observed Isc responses indicate a rapid modulation of electrolyte transport in Caco-2 cells by EPEC, including stimulation of chloride secretion, for which signal transduction to host cells is a prerequisite. 



Keywords: enteropathogenic Escherichia coli; Caco-2 cells; Ussing chambers; electrolyte transport; signal transduction

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Figure 1 .

Figure 1

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Transmission electron micrographs of EPEC adhesion to Caco-2 monolayers. On initial infection, both wild type strain E2348/69 (a) and cfm strain 14.2.1(1) adhered to intact brush border microvilli. After 15 minutes, E23438/69 were intimately attached to the apical membrane devoid of microvilli (b); however, even after 60 minutes, 14.2.1(1) did not intimately adhere to host cells (c). Original magnification: × 17 500. 


Figure 2 .

Figure 2

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(a) Short circuit current (Isc; µA/cm2) and (b) transepithelial electrical resistance (TEER; Ω.cm2) in uninfected Caco-2 monolayers, and those infected with EPEC strain E2348/69 or cfm 14.2.1(1). Each point represents the mean (SEM) from nine monolayers, unless otherwise indicated in parentheses. *p<0.05 v uninfected or 14.2.1(1) infected monolayers; †p<0.05 v uninfected monolayers only. 


Figure 3 .

Figure 3

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Cl dependence of short circuit current (Isc; µA/cm2) in uninfected Caco-2 monolayers and those infected with EPEC strain E2348/69. The Isc of uninfected monolayers did not differ significantly between Cl -inclusive and Cl -free bathing solutions; each point represents the mean (SEM) of seven monolayers. The rapid increase in Isc induced by E2348/69 in Cl -inclusive bathing solution was significantly reduced in Cl -free solution; each point represents mean Isc (SEM) from nine monolayers. *p<0.05 v uninfected or 14.2.1(1) infected monolayers; †p<0.05 v uninfected monolayers. 


Figure 4 .

Figure 4

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Effect of amphotericin B (10 µg/ml apical application) on short circuit current (Isc; µA/cm2) in uninfected Caco-2 monolayers and those infected with EPEC strain E2348/69. Values presented were determined 15 minutes after initial infection. Although E2348/69 infection or amphotericin B treatment induced increases in Isc, these effects were not cumulative. Each bar represents the mean (SEM) from three monolayers. *p<0.05 v control (uninfected and untreated) monolayers. 


Figure 5 .

Figure 5

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Amino acid dependence of (a) short circuit current (Isc; µA/cm2) and (b) change in transepithelial electrical resistance (TEER; expressed as % of TEER at 10 minutes) in uninfected Caco-2 monolayers and those infected with EPEC strain E2348/69. The Isc of uninfected monolayers did not differ significantly between amino acid-inclusive and amino acid-free bathing solutions; each point represents the mean (SEM) from eight monolayers. The rapid and sustained increase in Isc induced by E2348/69 in amino acid-inclusive bathing solution was significantly reduced in amino acid-free solution; each point represents the mean (SEM) from five monolayers. Loss of TEER associated with E2348/69 infection did not occur under amino acid-free conditions. *p<0.05 v infected monolayers in amino acid-free bathing solution. 


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