title: Leukotriene B(4) stimulates Rac-ERK cascade to generate reactive oxygen species that mediates chemotaxis.
abstract: Leukotriene B(4) is a potent chemoattractant known to be involved mainly in inflammation, immune responses, and host defense against infection, although the exact signaling mechanisms by which it exerts its effects are not well understood. Here we show that exogenous leukotriene B(4) induces reactive oxygen species (ROS) generation via a Rac-dependent pathway, and that stable expression of Rac(N17), a dominant negative Rac1 mutant, completely blocks leukotriene B(4)-induced ROS generation. In addition, leukotriene B(4)-induced ROS generation is selectively blocked by inhibition of ERK or cytosolic phospholipase A(2), but not p38 kinase, which is indicative of its dependence on ERK activation and synthesis of arachidonic acid. Consistent with those findings, leukotriene B(4) Rac-dependently stimulates ERK and cytosolic phospholipase A(2) activity, and transient transfection with plasmid expressing Rac(V12), a constitutively activated Rac1 mutant, also dose-dependently stimulates ERK activity. Our findings suggest that ERK and cytosolic phospholipase A(2) are situated downstream of Rac, and we conclude that Rac, ERK, and cytosolic phospholipase A(2) all play pivotal roles in mediating the ROS generation that appears to be a prerequisite for leukotriene B(4)-induced chemotaxis and cell proliferation.
authors.affiliation: Graduate School of Biotechnology, Korea University, 5-1 Anam-dong, Seoul 136-701, Korea.
authors.forename: Chang-Hoon
authors.initials: CH
authors.lastname: Woo
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: You
authors.forename: Sung-Hoon
authors.initials: SH
authors.lastname: Cho
authors.forename: Young-Woo
authors.initials: YW
authors.lastname: Eom
authors.forename: Jang-Soo
authors.initials: JS
authors.lastname: Chun
authors.forename: Yung-Joon
authors.initials: YJ
authors.lastname: Yoo
authors.forename: Jae-Hong
authors.initials: JH
authors.lastname: Kim
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D002633:Chemotaxis; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D005799:Genes, Dominant; D006861:Hydrogen Peroxide / Q000378:metabolism; D015151:Immunoblotting; D007975:Leukotriene B4 / Q000737:chemistry* / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D051381:Rats; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D007975:Leukotriene B4; D016718:Arachidonic Acid; D006861:Hydrogen Peroxide; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein