title: Cooperative and redundant signaling of leukotriene B4 and leukotriene D4 in human monocytes.
abstract: BACKGROUND
  Leukotriene B(4) (LTB(4)) and cysteinyl leukotrienes (cysLTs) are important immune mediators, often found concomitantly at sites of inflammation. Although some of the leukotriene-mediated actions are distinctive (e.g., bronchial constriction for cysLTs), many activities such as leukocyte recruitment to tissues and amplification of inflammatory responses are shared by both classes of leukotrienes.
  
  
  OBJECTIVE
  We used human monocytes to characterize leukotriene-specific signaling, gene expression signatures, and functions and to identify interactions between LTB(4)- and cysLTs-induced pathways.
  
  
  METHODS
  Responsiveness to leukotrienes was assessed using oligonucleotide microarrays, real-time PCR, calcium mobilization, kinase activation, and chemotaxis assays.
  
  
  RESULTS
  Human monocytes were found to express mRNA for high- and low-affinity LTB(4) receptors, BLT(1) and BLT(2), but signal predominantly through BLT(1) in response to LTB(4) stimulation as shown using selective agonists, inhibitors, and gene knock down experiments. LTB(4) acting through BLT(1) coupled to G-protein α inhibitory subunit activated calcium signaling, p44/42 mitogen-activated protein kinase, gene expression, and chemotaxis. Twenty-seven genes, including immediate early genes (IEG), transcription factors, cytokines, and membrane receptors were significantly up-regulated by LTB(4). LTB(4) and LTD(4) had similar effects on signaling, gene expression, and chemotaxis indicating redundant cell activation pathways but costimulation with both lipid mediators was additive for many monocyte functions.
  
  
  CONCLUSIONS
  Leukotriene B(4) and LTD(4) display both redundant and cooperative effects on intracellular signaling, gene expression, and chemotaxis in human monocytes. These findings suggest that therapies targeting either leukotriene alone may be less effective than approaches directed at both.
authors: Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD, USA.
authors: L Y
authors: LY
authors: Chen
authors: M
authors: M
authors: Eberlein
authors: S
authors: S
authors: Alsaaty
authors: A
authors: A
authors: Martinez-Anton
authors: J
authors: J
authors: Barb
authors: P J
authors: PJ
authors: Munson
authors: R L
authors: RL
authors: Danner
authors: Y
authors: Y
authors: Liu
authors: C
authors: C
authors: Logun
authors: J H
authors: JH
authors: Shelhamer
authors: G
authors: G
authors: Woszczek
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