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Hydrogen peroxide inhibits colonic epithelial ion transport by MAP kinase and PI3‐kinase (PI3K) independently of activated epidermal growth factor receptor (EGFr)
Author(s) -
McCole Declan F.,
Barrett Kim E.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1161-a
Subject(s) - epidermal growth factor receptor , chemistry , egfr inhibitors , phosphorylation , mapk/erk pathway , cancer research , erbb3 , epidermal growth factor , pi3k/akt/mtor pathway , kinase , microbiology and biotechnology , signal transduction , receptor , biology , biochemistry
Reactive oxygen species contribute to epithelial damage and dysfunction in inflammatory bowel disease (IBD). We have shown that hydrogen peroxide (H 2 O 2 ) inhibits intestinal Ca 2+ ‐dependent ion transport by PI3K‐and MAP kinase‐dependent mechanisms, while also activating the EGFr. Here, we studied whether EGFr regulates H 2 O 2 ‐mediated inhibition of ion transport in colonic epithelial cells. Protein phosphorylation was measured in T 84 colonic epithelial monolayers by Western blot, and ion transport was measured in Ussing chambers. H 2 O 2 (500 μM) increased EGFr tyrosine phosphorylation and its association with the catalytic p110β subunit of PI3‐K in T 84 cells. However, neither an EGFr kinase inhibitor, tyrphostin AG1478 (1 μM), nor a neutralizing anti‐EGFr antibody that blocks the EGFr ligand binding domain (5 μg/ml), had any significant effect on H 2 O 2 ‐induced activation of ERK or the PI3‐K target, Akt1. Both AG1478 and anti‐EGFr inhibited H 2 O 2 ‐induced EGFr activation indicating that H 2 O 2 can activate EGFr via EGFr ligand release. Tyrphostin AG1478 also had no effect on H 2 O 2 inhibition of CCh‐stimulated Cl ‐ secretion across T 84 monolayers. In summary, H 2 O 2 activates EGFr in colonic epithelial cells, probably via the release of an EGFr ligand, but this effect does not account for inhibition of Ca 2+ ‐dependent Cl − secretion by H 2 O 2 . Because we have previously shown that EGFr activated by other means can lead to inhibition of Cl − secretion, our data imply selective outcomes of EGFr signaling depending on its mode of activation. Supported by the Crohn's and Colitis Foundation of America and NIH.