title: Bruton's tyrosine kinase is required for TLR-dependent heme oxygenase-1 gene activation via Nrf2 in macrophages.
abstract: Heme oxygenase (HO)-1 is the inducible isoform of the rate-limiting enzyme of heme degradation and provides cytoprotection against oxidative stress by its products carbon monoxide and biliverdin. More recently, HO-1 has also been shown to exert immunomodulatory functions via cell type-specific anti-inflammatory effects in myeloid/macrophage cells. In the current study, it is demonstrated that Bruton's tyrosine kinase (Btk), the gene of which is mutated in the human immunodeficiency X-linked agammaglobulinemia, is involved in the upregulation of HO-1 gene expression via TLR signaling in macrophages. The specific Btk inhibitor LFM-A13 blocked HO-1 induction by the classical TLR4 ligand LPS in cell cultures of RAW264.7 monocytic cells and primary mouse alveolar macrophages. Moreover, upregulation of HO-1 gene expression was abrogated in LPS-stimulated alveolar macrophages from Btk(-/-) mice. Transfection studies with luciferase reporter gene constructs demonstrated that LPS-dependent induction of HO-1 promoter activity was attenuated by pharmacological Btk inhibition and by an overexpressed dominant-negative mutant of Btk. This induction was mediated by the transcription factor Nrf2, which is a master regulator of the antioxidant cellular defense. Accordingly, nuclear translocation of Nrf2 in LPS-treated macrophages was reduced by Btk inhibition. The generation of reactive oxygen species, but not that of NO, was involved in this regulatory pathway. Btk-dependent induction of HO-1 gene expression was also observed upon macrophage stimulation with ligands of TLR2, TLR6, TLR7, and TLR9, suggesting that Btk is required for HO-1 gene activation by major TLR pathways.
authors.affiliation: Institute for Anatomy and Cell Biology II, Justus Liebig University Giessen, Giessen 35390, Germany.
authors.forename: Vijith
authors.initials: V
authors.lastname: Vijayan
authors.forename: Eveline
authors.initials: E
authors.lastname: Baumgart-Vogt
authors.forename: Srivatsava
authors.initials: S
authors.lastname: Naidu
authors.forename: Guofeng
authors.initials: G
authors.lastname: Qian
authors.forename: Stephan
authors.initials: S
authors.lastname: Immenschuh
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000361:Agammaglobulinemia / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000276:immunology; D040181:Genetic Diseases, X-Linked / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D051547:Heme Oxygenase-1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D008070:Lipopolysaccharides / Q000502:physiology; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D051267:NF-E2-Related Factor 2 / Q000502:physiology*; D009570:Nitriles / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D051193:Toll-Like Receptors / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics / Q000276:immunology*
chemical_list: D000577:Amides; C118451:LFM A13; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D009570:Nitriles; D047428:Protein Kinase Inhibitors; D051193:Toll-Like Receptors; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; C000625951:Btk protein, mouse