12223352

pubmed:Citation

4

IFN-gamma inhibits intestinal Cl(-) secretion, in part via downregulation of CFTR and Na(+)-K(+)-ATPase activity and expression, but the proximal signaling events were unknown. We have shown that transforming growth factor-alpha (TGF-alpha) inhibits calcium-activated Cl(-) secretion, and effects of IFN-gamma in other systems are mediated via EGF family members. We tested whether IFN-gamma inhibits Cl(-) secretion via EGF receptor (EGFr) activation. IFN-gamma increased tyrosine phosphorylation in T84 cells at 24 h, including the EGFr. IFN-gamma also increased cell-associated pro-TGF-alpha, as well as free TGF-alpha in the bathing media. However, whereas IFN-gamma significantly inhibited carbachol-induced Cl(-) secretion, neither neutralizing antibodies to TGF-alpha nor an EGFr inhibitor (1 microM tyrphostin AG 1478) were able to reverse this inhibitory effect. AG 1478 also failed to reverse IFN-gamma-induced tyrosine phosphorylation of the EGFr, but receptor phosphorylation was attenuated by both the neutralizing antibody to TGF-alpha and PP2, a Src kinase inhibitor. Moreover, PP2 reversed the inhibitory effect of IFN-gamma on Cl(-) secretion. In total, our findings suggest an increase in functional TGF-alpha and activation of the EGFr in response to IFN-gamma. The release of TGF-alpha and intracellular Src activation likely combine to mediate EGFr phosphorylation, but only Src appears to contribute to the inhibition of transport. Nevertheless, because TGF-alpha plays a role in restitution and repair of the intestinal epithelium after injury, we speculate that these findings reflect a feedback loop whereby IFN-gamma modulates the extent of cytokine-induced intestinal damage.

eng

IM

MEDLINE

0193-1857

Print

NLM

G923-31

pubmed-meshheading:12223352-Antibodies, pubmed-meshheading:12223352-Blotting, Western, pubmed-meshheading:12223352-Carbachol, pubmed-meshheading:12223352-Cell Line, pubmed-meshheading:12223352-Cell Membrane, pubmed-meshheading:12223352-Chlorides, pubmed-meshheading:12223352-Colon, pubmed-meshheading:12223352-Enzyme Inhibitors, pubmed-meshheading:12223352-Humans, pubmed-meshheading:12223352-Immunosorbent Techniques, pubmed-meshheading:12223352-Interferon-gamma, pubmed-meshheading:12223352-Intestinal Mucosa, pubmed-meshheading:12223352-Kinetics, pubmed-meshheading:12223352-Phosphorylation, pubmed-meshheading:12223352-Phosphotyrosine, pubmed-meshheading:12223352-Protein Tyrosine Phosphatases, pubmed-meshheading:12223352-Pyrimidines, pubmed-meshheading:12223352-Receptor, Epidermal Growth Factor, pubmed-meshheading:12223352-Transforming Growth Factor alpha, pubmed-meshheading:12223352-Tyrphostins, pubmed-meshheading:12223352-src-Family Kinases

Interferon-gamma activates EGF receptor and increases TGF-alpha in T84 cells: implications for chloride secretion.

Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't