Enteropathogenic Escherichia coli (EPEC), a food-borne human pathogen, is responsible for
infantile diarrhea, especially in developing countries. The pathophysiology of EPEC-induced
diarrhea, however, is not completely understood. Our recent studies showed modulation of Na+/H+ and Cl-/HCO3- exchange activities in Caco-2 cells in response to EPEC
infection. We hypothesized that intestinal
short-chain fatty acid absorption mediated by monocarboxylate transporter 1 (MCT1) might also be altered by EPEC
infection. The aim of the current studies was to examine the effect of EPEC
infection on
butyrate uptake. Caco-2 cells were infected with wild-type EPEC, various mutant strains, or nonpathogenic E. coli HS4, and [14C]
butyrate uptake was determined. EPEC, but not nonpathogenic E. coli, significantly decreased
butyrate uptake.
Infection of cells with strains harboring mutations in escN, which encodes a putative
ATPase for the EPEC
type III secretion system (TTSS), or in the espA, espB, or espD genes encoding structural components of the TTSS, had no effect on
butyrate uptake, indicating the TTSS dependence. On the other hand, strains with mutations in the effector
protein genes espF, espG, espH, and map inhibited
butyrate uptake, similar to the wild-type EPEC. Surface expression of MCT1 decreased considerably after EPEC but not after nonpathogenic E. coli
infection. In conclusion, our studies demonstrate inhibition of MCT1-mediated
butyrate uptake in Caco-2 cells in response to EPEC
infection. This inhibition was dependent on a functional TTSS and the structural
proteins EspA, -B, and -D of the translocation apparatus.