title: Activation of phosphatidylinositol 3-kinase by interleukin-13. An inhibitory signal for inducible nitric-oxide synthase expression in epithelial cell line HT-29.
abstract: The human colonic epithelial cell line HT-29 can be induced by a combination of the cytokines interleukin (IL)-1alpha, tumor necrosis factor alpha, and interferon-gamma to express the inducible form of nitric-oxide synthase (iNOS; Kolios, G., Brown, Z., Robson, R., Robertson, D. A. F., & Westwick, J. (1995) Br. J. Pharmacol. 116, 2866-2872). IL-13 is a potent inhibitor of cytokine-induced iNOS mRNA expression and nitric oxide generation in HT-29 cells via an unknown mechanism. We report here that in HT-29 cells, IL-13 induces a concentration and time-dependent increase in the formation of the lipid products of phosphatidylinositol (PtdIns) 3-kinase, namely phosphatidylinositol (3,4)-bisphosphate and phosphatidylinositol (3,4,5)-trisphosphate. IL-13 also induces a parallel concentration and time-dependent increase in the in vitro lipid kinase activity present in immunoprecipitates of the p85 regulatory subunit of PtdIns 3-kinase. In addition, we also demonstrate that IL-13 stimulates the tyrosine phosphorylation of the adaptor molecule insulin receptor substrate 1, which may facilitate receptor coupling to PtdIns 3-kinase. Both the increases in D-3 phosphatidylinositol lipids and the increased in vitro lipid kinase activity of p85 immunoprecipitates were inhibited by wortmannin and LY294002. Inhibition of the PtdIns 3-kinase activity was paralleled by a reversal of the ability of IL-13 to inhibit iNOS mRNA expression and nitrite generation in HT-29 cells. These data demonstrate that the activation of PtdIns 3-kinase by IL-13 is a key signal that is responsible for the inhibition of iNOS transcription in activated epithelial cells.
authors.affiliation: Department of Pharmacology, Bath University, Claverton Down, Bath, Avon BA2 7AY, United Kingdom.
authors.forename: K
authors.initials: K
authors.lastname: Wright
authors.forename: S G
authors.initials: SG
authors.lastname: Ward
authors.forename: G
authors.initials: G
authors.lastname: Kolios
authors.forename: J
authors.initials: J
authors.lastname: Westwick
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004848:Epithelium / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D018793:Interleukin-13 / Q000494:pharmacology*; D009025:Morpholines / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000235:genetics; D009573:Nitrites / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D010716:Phosphatidylinositols / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases; D014443:Tyrosine / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D000894:Anti-Inflammatory Agents, Non-Steroidal; D002867:Chromones; D004791:Enzyme Inhibitors; D055504:Insulin Receptor Substrate Proteins; D018793:Interleukin-13; D009025:Morpholines; D019001:Nitric Oxide Synthase; D009573:Nitrites; D019869:Phosphatidylinositol 3-Kinases; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D014443:Tyrosine; D000077191:Wortmannin; C526292:IRS1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one