title: Differential regulation of Na+/H+ exchange isoform activities by enteropathogenic E. coli in human intestinal epithelial cells.
abstract: Enteropathogenic Escherichia coli (EPEC) is an important human intestinal foodborne pathogen associated with diarrhea, especially in infants and young children. Although EPEC produces characteristic attaching and effacing lesions and loss of microvilli, the pathophysiology of EPEC-associated diarrhea, particularly during early infection, remains elusive. The present studies were designed to examine the direct effects of EPEC infection on intestinal absorption via Na(+)/H(+) exchanger (NHE) isoforms. Caco-2 cells were infected with EPEC strain E2348/69 or nonpathogenic E. coli HB101 for a period of 60 to 120 min. Total NHE activity was significantly increased at 60 min, reaching approximately threefold increase after 90 min of EPEC infection. Similar findings were seen in HT-29 cells and T84 cells indicating that the response was not cell-line specific. Most surprising was the differential regulation of NHE2 and NHE3 by EPEC. Marked activation of NHE2 (300%) occurred, whereas significant inhibition ( approximately 50%) of NHE3 activity was induced. The activity of basolateral isoform NHE1 was also significantly increased in response to EPEC infection. Mutations that disrupted the type III secretion system (TTSS) ablated the effect of EPEC on the activity of both NHE2 and NHE3. These results suggest that EPEC, through a TTSS-dependent mechanism, exerts differential effects on NHE isoform activity in intestinal epithelial cells. Additionally, NHEs do not appear to play any role in EPEC-mediated inflammation, because the NHE inhibitors amiloride and 5-(N-ethyl-N-isopropyl)amiloride did not prevent EPEC-mediated IkappaBalpha degradation.
authors.affiliation: Univ. of Illinois at Chicago, Medical Research Service (600/151 Chicago Veterans Affairs Health Care System, 820 S. Damen Ave., Chicago, IL 60612, USA.
authors.forename: Gail
authors.initials: G
authors.lastname: Hecht
authors.forename: Kim
authors.initials: K
authors.lastname: Hodges
authors.forename: Ravinder K
authors.initials: RK
authors.lastname: Gill
authors.forename: Fely
authors.initials: F
authors.lastname: Kear
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Tyagi
authors.forename: Jaleh
authors.initials: J
authors.lastname: Malakooti
authors.forename: Krishnamurthy
authors.initials: K
authors.lastname: Ramaswamy
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Dudeja
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000378:metabolism; D004751:Enteritis / Q000382:microbiology / Q000517:prevention & control; D004927:Escherichia coli Infections / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000166:cytology / Q000382:microbiology*; D007425:Intracellular Membranes / Q000378:metabolism; D009997:Osmotic Pressure; D020033:Protein Isoforms / Q000378:metabolism; D012964:Sodium / Q000493:pharmacokinetics; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013997:Time Factors
chemical_list: D029968:Escherichia coli Proteins; D020033:Protein Isoforms; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D012964:Sodium; C039614:ethylisopropylamiloride