title: Lipopolysaccharide-mediated reactive oxygen species and signal transduction in the regulation of interleukin-1 gene expression.
abstract: Lipopolysaccharide (LPS) stimulates macrophages to release inflammatory cytokines, interleukin-1 beta (IL-1), and tumor necrosis factor (TNF). LPS-induced TNF suppresses scavenger receptor functions in macrophages (van Lenten, B. J., and Fogelman, A. M. (1992) J. Immunol. 148, 112-116), which is regulated by TNF-mediated protein kinases (Hsu, H. Y., and Twu, Y. C. (2000) J. Biol. Chem. 275, 41035-41048). To examine the molecular mechanism for LPS induction of IL-1 in macrophages, we demonstrated that LPS quickly stimulated reactive oxygen species (ROS), and 3 h later induced prointerleukin-1 beta (pro-IL-1, precursor of IL-1) production and IL-1 secretion. LPS stimulated pro-IL-1 message/protein between 3 and 10 h; however, there was a 40% reduction of pro-IL-1 in preincubation of the antioxidant, N-acetylcysteine (NAC). Moreover, NAC moderated LPS-induced IL-1 secretion partially via interleukin 1-converting enzyme. The maximal activity of LPS-induced ERK, JNK, and p38 was 12- (30 min), 5- (30 min), and 16-fold (15 min), respectively. In contrast, NAC reduced ERK activity to 60% and decreased p38 activity to the basal level, but JNK activity was induced 2-fold. Furthermore, the pharmacological antagonists LY294002, SB203580, curcumin, calphostin C, and PD98059 revealed the diverse roles of LPS-mediated protein kinases in pro-IL-1. On the other hand, NAC and diphenyleneiodonium chloride partially inhibited LPS-induced Rac activity and protein-tyrosine kinase (PTK), indicating that LPS-mediated ROS and NADPH oxidase correspond to Rac activation and IL-1 expression. Our findings establish for the first time that LPS-mediated PTK/phosphatidylinositol 3-kinase/Rac/p38 pathways play a more important role than pathways of PTK/PKC/MEK/ERK and of PTK/phosphatidylinositol 3-kinase/Rac/JNK in the regulation of pro-IL-1/IL-1. The findings also further elucidate the critical role of LPS-mediated ROS in signal transduction pathways. Our results suggest that understanding LPS-transduced signals in IL-1 induction upon the antibacterial action of macrophages should provide a therapeutic strategy for aberrant inflammatory responses leading to severe cellular injury or concurrent multiorgan septic damage.
authors.affiliation: Faculty of Medical Technology, Institute of Biotechnology in Medicine, National Yang-Ming University, 112 Taipei, Taiwan. hyhsu@ym.edu.tw
authors.forename: Hsien-Yeh
authors.initials: HY
authors.lastname: Hsu
authors.forename: Meng-Hsuan
authors.initials: MH
authors.lastname: Wen
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D003474:Curcumin / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation; D005799:Genes, Dominant / Q000235:genetics; D007093:Imidazoles / Q000494:pharmacology; D007375:Interleukin-1 / Q000096:biosynthesis* / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D008070:Lipopolysaccharides / Q000378:metabolism*; D048670:MAP Kinase Kinase 4; D008264:Macrophages / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D011485:Protein Binding; D011725:Pyridines / Q000494:pharmacology; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D009025:Morpholines; D009281:Naphthalenes; D011725:Pyridines; D017382:Reactive Oxygen Species; C015482:protein kinase modulator; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D020830:rac1 GTP-Binding Protein; C058819:calphostin C; D003474:Curcumin; C093642:SB 203580; D010100:Oxygen; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one