title: Thromboxane A2 promotes interleukin-6 biosynthesis mediated by an activation of cyclic AMP-response element-binding protein in 1321N1 human astrocytoma cells.
abstract: 1321N1 human astrocytoma cells express thromboxane A2 (TXA2) receptors (TP). However, physiological consequences of TXA2 signaling in glial cells remain unclear. Herein, we show that TXA2 promotes interleukin-6 (IL-6) biosynthesis in glial cells. A TP agonist, 9,11-dideoxy-9alpha,11alpha-methanoepoxy-prosta-5Z,13E-dien-1-oic acid (U46619), enhanced IL-6 production in both 1321N1 cells and cultured mouse astrocytes. It has been shown that IL-6 gene expression is regulated by various transcription factors. Among them, we found a significant increase in cyclic AMP-response element-binding protein (CREB) activity with its phosphorylation at Ser133 by U46619 in 1321N1 cells. Although U46619 increased IL-6 promoter activity, a mutation at cyclic AMP-response element (CRE) on the promoter clearly suppressed the effect, suggesting that CRE is involved in U46619-induced IL-6 expression. Furthermore, both CREB and IL-6 promoter activities were suppressed by SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole], a p38 mitogen-activated protein kinase (MAPK) inhibitor, and H89 [N-[2-(4-bromocinnamylamino)-ethyl]-5-isoquinoline], a protein kinase A (PKA) inhibitor, indicating involvements of p38 MAPK and PKA in CREB activation and IL-6 expression. To determine which G-proteins are implicated in the U46619-induced IL-6 synthesis, the interfering mutants of Galpha(q), Galpha12, or Galpha13 by were overexpressed in 1321N1 cells adenoviral approach. It is noteworthy that the Galpha(q) or Galpha13 mutant blocked the IL-6 production by U46619. The constitutively active mutant of Galpha(q), Galpha12, or Galpha13 enhanced IL-6 production, indicating that Galpha(q) and Galpha13 were involved in U46619-induced IL-6 production. In conclusion, TXA2 enhances the IL-6 biosynthesis via the PKA p38 MAPK/CREB pathway in 1321N1 cells. IL-6 induction depends on Galpha(q) and Galpha13 as well. This is the first report showing TP-mediated IL-6 production in glial cells.
authors.affiliation: Department of Cellular Signaling, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan. obaray@mail.pharm.tohoku.ac.jp
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Obara
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kurose
authors.forename: Norimichi
authors.initials: N
authors.lastname: Nakahata
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D001254:Astrocytoma / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D001483:Base Sequence; D015153:Blotting, Western; D050882:CREB-Binding Protein; D045744:Cell Line, Tumor; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013928:Thromboxane A2 / Q000494:pharmacology*; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D015850:Interleukin-6; D009687:Nuclear Proteins; D015534:Trans-Activators; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases