Leukotriene B4 amplifies NF-κB activation in mouse macrophages by reducing SOCS1 inhibition of MyD88 expression
Carlos H. Serezani, … , Sonia Jancar, Marc Peters-Golden
Carlos H. Serezani, … , Sonia Jancar, Marc Peters-Golden
Published January 4, 2011
Citation Information: J Clin Invest. 2011;121(2):671-682. https://doi.org/10.1172/JCI43302.
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Research Article Inflammation

Leukotriene B4 amplifies NF-κB activation in mouse macrophages by reducing SOCS1 inhibition of MyD88 expression

Abstract

Activation of NF-κB and 5-lipoxygenase–mediated (5-LO–mediated) biosynthesis of the lipid mediator leukotriene B4 (LTB4) are pivotal components of host defense and inflammatory responses. However, the role of LTB4 in mediating innate immune responses elicited by specific TLR ligands and cytokines is unknown. Here we have shown that responses dependent on MyD88 (an adaptor protein that mediates signaling through all of the known TLRs, except TLR3, as well as IL-1β and IL-18) are reduced in mice lacking either 5-LO or the LTB4 receptor BTL1, and that macrophages from these mice are impaired in MyD88-dependent activation of NF-κB. This macrophage defect was associated with lower basal and inducible expression of MyD88 and reflected impaired activation of STAT1 and overexpression of the STAT1 inhibitor SOCS1. Expression of MyD88 and responsiveness to the TLR4 ligand LPS were decreased by Stat1 siRNA silencing in WT macrophages and restored by Socs1 siRNA in 5-LO–deficient macrophages. These results uncover a pivotal role in macrophages for the GPCR BLT1 in regulating activation of NF-κB through Stat1-dependent expression of MyD88.

Authors

Carlos H. Serezani, Casey Lewis, Sonia Jancar, Marc Peters-Golden

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Figure 3

LTB4 is required for MyD88 expression in phagocytes.

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LTB4 is required for MyD88 expression in phagocytes. (A) MyD88, TIRA...
(A) MyD88, TIRAP, TRIF, and TIRP protein expression in WT macrophages and in 5-LO–/– and BLT1–/– macrophages treated for 24 hours with or without LTB4. (B) Densitometry of MyD88 protein in 5-LO–/– and BLT1–/– macrophages. (C) Myd88 mRNA expression in 5-LO–/– and BLT1–/– macrophages treated as in A. (B and C) Data are representative of 3 experiments, performed in triplicate; values are relative to control WT macrophages (dashed line). *P < 0.05 versus WT; #P < 0.001 versus untreated 5-LO–/–. (D) MyD88 protein expression in resident peritoneal (PM), alveolar (AM), and splenic (SM) macrophages as well as splenic DCs, T and B lymphocytes, and lung fibroblasts from WT and 5-LO–/– mice. Data are representative of 3 experiments. (E) Myd88 mRNA decay in WT and 5-LO–/– macrophages harvested after treatment with actinomycin D (2.5 mg/ml). Data are from 3 experiments in triplicate; values are relative to untreated macrophages from both genotypes. (F) MyD88 protein in WT and 5-LO–/– macrophages incubated for 24 hours as indicated. Immunoblot results are from 2–3 independent experiments (relative MyD88 density shown by numbers beneath). Lanes were run on the same gel but were noncontiguous (white line). (G) Nitrite production in WT and 5-LO–/– macrophages pretreated for 24 hours with or without LTB4, followed by LPS for another 24 hours. Data are representative of 3 experiments. *P < 0.05 versus control; #P < 0.05 versus non–LTB4-treated stimulated WT; &P < 0.01 versus LPS or IL-1β alone.