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 7

LTB4/BLT1 signaling is required to restrain SOCS1 expression.

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LTB4/BLT1 signaling is required to restrain SOCS1 expression. (A) WT...
(A) WT and 5-LO–/– or BLT1–/– macrophages were treated for 24 hours with or without LTB4 and SOCS1 expression was determined by immunoblotting. Immunoblots are representative of 3 independent experiments. Mean ± SEM densitometric values for SOCS1 protein in 5-LO–/– and BLT1–/– macrophages from 3 independent experiments were normalized for actin and expressed relative to untreated WT control (dashed line). (B) Socs1 mRNA expression by real-time RT-PCR in 5-LO–/– and BLT1–/– macrophages treated for 24 hours with or without LTB4, expressed relative to untreated WT control (dashed line). Data are mean ± SEM from 3 individual experiments, each performed in triplicate. (C) WT and 5-LO–/– macrophages were pretreated with PTX (600 ng/ml) for 48 hours, after which RNA was isolated for Socs1 mRNA determination by real-time RT-PCR. Data are mean ± SEM from 3 individual experiments, each performed in triplicate. (D) Socs1 mRNA decay in WT and 5-LO–/– macrophages. Cells were pretreated with or without LTB4 for 5 minutes, followed by addition of actinomycin D (2.5 mg/ml); cells were harvested at the indicated times and Socs1 mRNA was measured by real-time RT-PCR. Data are mean ± SEM from 3 individual experiments, each performed in triplicate; values are relative to untreated macrophages of the appropriate genotype. *P < 0.05 versus WT control; #P < 0.05 versus untreated 5-LO–/–.