Hemorrhagic shock recruits Toll-like receptor 4 to the plasma membrane in macrophages: A novel mechanism of cell priming for LPS signaling

Oxidative stress generated by ischemia/reperfusion is known to prime inflammatory cells for increased responsiveness to subsequent stimuli, such as lipopolysaccharide (LPS). The mechanism(s) underlying this effect remains poorly elucidated. These studies show that alveolar macrophages recovered from rodents subjected to hemorrhagic shock/resuscitation expressed increased surface levels of Toll-like receptor 4 (TLR4), an effect inhibited by adding the antioxidant N-acetylcysteine to the resuscitation fluid. Consistent with a role for oxidative stress in this effect, in vitro H2O2 treatment of RAW 264.7 macrophages similarly caused an increase in surface TLR4. The H2O2-induced increase in surface TLR4 was prevented by depleting intracellular calcium or disrupting the cytoskeleton, suggesting the involvement of receptor exocytosis. Further, fluorescent resonance energy transfer between TLR4 and the raft marker GM1 as well as biochemical analysis of the raft components demonstrated that oxidative stress redistributes TLR4 to lipid rafts in the plasma membrane. Preventing the oxidant-induced movement of TLR4 to lipid rafts using methyl-β-cyclodextrin precluded the increased responsiveness of cells to LPS after H2O2 treatment. Collectively, these studies suggest a novel mechanism whereby oxidative stress might prime the responsiveness of cells of the innate immune system.

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Oxidative stress generated by hemorrhagic shock recruits Toll-like receptor 4 to the plasma membrane in macrophages

The Journal of Cell Biology ◽

10.1083/jcb1743oia6 ◽

2006 ◽

Vol 174 (3) ◽

pp. i6-i6

Author(s):

Kinga A. Powers ◽

Katalin Szászi ◽

Rachel G. Khadaroo ◽

Patrick S. Tawadros ◽

John C. Marshall ◽

...

Keyword(s):

Oxidative Stress ◽

Plasma Membrane ◽

Hemorrhagic Shock ◽

Toll Like Receptor ◽

Toll Like Receptor 4

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Signaling for myocardial depression in hemorrhagic shock: roles of Toll-like receptor 4 and p55 TNF-α receptor

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00182.2004 ◽

2005 ◽

Vol 288 (3) ◽

pp. R600-R606 ◽

Cited By ~ 35

Author(s):

Xianzhong Meng ◽

Lihua Ao ◽

Yong Song ◽

Christopher D. Raeburn ◽

David A. Fullerton ◽

...

Keyword(s):

Hemorrhagic Shock ◽

Gene Knockout ◽

Left Ventricular ◽

Toll Like Receptor ◽

Myocardial Depression ◽

Toll Like Receptor 4 ◽

Proinflammatory Mediators ◽

Cellular Expression ◽

Tnf Α ◽

Myocardial Contractile

Hemorrhagic shock causes myocardial contractile depression. Although this myocardial disorder is associated with increased expression of tumor necrosis factor-α (TNF-α), the role of TNF-α as a myocardial depressant factor in hemorrhagic shock remains to be determined. Moreover, it is unclear which TNF-α receptor mediates the myocardial depressive effects of TNF-α. Toll-like receptor 4 (TLR4) regulates cellular expression of proinflammatory mediators following lipopolysaccharide stimulation and may be involved in the tissue inflammatory response to injury. The contribution of TLR4 signaling to tissue TNF-α response to hemorrhagic shock and TLR4’s role in myocardial depression during hemorrhagic shock are presently unknown. We examined the relationship of TNF-α production to myocardial depression in a mouse model of nonresuscitated hemorrhagic shock, assessed the influence of TLR4 mutation, resulting in defective signaling, on TNF-α production and myocardial depression, and determined the roles of TNF-α and TNF-α receptors in myocardial depression using a gene knockout (KO) approach. Hemorrhagic shock resulted in increased plasma and myocardial TNF-α (4.9- and 4.5-fold, respectively) at 30 min and induced myocardial contractile depression at 4 h. TLR4 mutation abolished the TNF-α response and attenuated myocardial depression (left ventricular developed pressure of 43.0 ± 6.2 mmHg in TLR4 mutant vs. 30.0 ± 3.6 mmHg in wild type, P < 0.05). TNF-α KO also attenuated myocardial depression in hemorrhagic shock, and the p55 receptor KO, but not the p75 receptor KO, mimicked the effect of TNF-α KO. The results suggest that TLR4 plays a novel role in signaling to the TNF-α response during hemorrhagic shock and that TNF-α through the p55 receptor activates a pathway leading to myocardial depression. Thus TLR4 and the p55 TNF-α receptor represent therapeutic targets for preservation of cardiac mechanical function during hemorrhagic shock.

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The Small GTPase Arf6 Is Essential for the Tram/Trif Pathway in TLR4 Signaling

Journal of Biological Chemistry ◽

10.1074/jbc.m113.499194 ◽

2013 ◽

Vol 289 (3) ◽

pp. 1364-1376 ◽

Cited By ~ 19

Author(s):

Tim Van Acker ◽

Sven Eyckerman ◽

Lieselotte Vande Walle ◽

Sarah Gerlo ◽

Marc Goethals ◽

...

Keyword(s):

Plasma Membrane ◽

Critical Role ◽

Adaptor Proteins ◽

Small Gtpase ◽

Toll Like Receptor ◽

Toll Like Receptor 4 ◽

Tlr4 Signaling ◽

Mouse Macrophages ◽

Adp Ribosylation Factor ◽

Irf3 Activation

Recognition of lipopolysaccharides (LPS) by Toll-like receptor 4 (TLR4) at the plasma membrane triggers NF-κB activation through recruitment of the adaptor proteins Mal and MyD88. Endocytosis of the activated TLR4 allows recruitment of the adaptors Tram and Trif, leading to activation of the transcription factor IRF3 and interferon production. The small GTPase ADP-ribosylation factor 6 (Arf6) was shown to regulate the plasma membrane association of Mal. Here we demonstrate that inhibition of Arf6 also markedly reduced LPS-induced cytokine production in Mal−/− mouse macrophages. In this article, we focus on a novel role for Arf6 in the MyD88-independent TLR4 pathway. MyD88-independent IRF3 activation and IRF3-dependent gene transcription were strictly dependent on Arf6. Arf6 was involved in transport of Tram to the endocytic recycling compartment and internalization of LPS, possibly explaining its requirement for LPS-induced IRF3 activation. Together, these results show a critical role for Arf6 in regulating Tram/Trif-dependent TLR4 signaling.

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Critical Role of Toll-Like Receptor 4 in Hypoxia-Inducible Factor 1α Activation During Trauma/Hemorrhagic Shock–Induced Acute Lung Injury After Lymph Infusion in Mice

Shock ◽

10.1097/shk.0000000000000212 ◽

2014 ◽

Vol 42 (3) ◽

pp. 271-278 ◽

Cited By ~ 8

Author(s):

Hong Jiang ◽

Rong Hu ◽

Lulu Sun ◽

Dongdong Chai ◽

Zhendong Cao ◽

...

Keyword(s):

Acute Lung Injury ◽

Lung Injury ◽

Hemorrhagic Shock ◽

Critical Role ◽

Hypoxia Inducible Factor ◽

Toll Like Receptor ◽

Toll Like Receptor 4 ◽

Hypoxia Inducible Factor 1Α

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Syntaxin 11 regulates the stimulus-dependent transport of Toll-like receptor 4 to the plasma membrane by cooperating with SNAP-23 in macrophages

Molecular Biology of the Cell ◽

10.1091/mbc.e18-10-0653 ◽

2019 ◽

Vol 30 (9) ◽

pp. 1085-1097 ◽

Cited By ~ 6

Author(s):

Daiki Kinoshita ◽

Chiye Sakurai ◽

Maya Morita ◽

Masashi Tsunematsu ◽

Naohiro Hori ◽

...

Keyword(s):

Plasma Membrane ◽

Intracellular Transport ◽

Resonance Energy Transfer ◽

Resonance Energy ◽

Interferon Γ ◽

Toll Like Receptor ◽

Toll Like Receptor 4 ◽

Protein Receptor ◽

Syntaxin 11 ◽

Dependent Transport

Syntaxin 11 (stx11) is a soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) that is selectively expressed in immune cells; however, its precise role in macrophages is unclear. We showed that stx11 knockdown reduces the phagocytosis of Escherichia coli in interferon-γ–activated macrophages. stx11 knockdown decreased Toll-like receptor 4 (TLR4) localization on the plasma membrane without affecting total expression. Plasma membrane–localized TLR4 was primarily endocytosed within 1 h by lipopolysaccharide (LPS) stimulation and gradually relocalized 4 h after removal of LPS. This relocalization was significantly impaired by stx11 knockdown. The lack of TLR4 transport to the plasma membrane is presumably related to TLR4 degradation in acidic endosomal organelles. Additionally, an immunoprecipitation experiment suggested that stx11 interacts with SNAP-23, a plasma membrane–localized SNARE protein, whose depletion also inhibits TLR4 replenishment in LPS-stimulated cells. Using an intramolecular Förster resonance energy transfer (FRET) probe for SNAP-23, we showed that the high FRET efficiency caused by LPS stimulation is reduced by stx11 knockdown. These findings suggest that stx11 regulates the stimulus-dependent transport of TLR4 to the plasma membrane by cooperating with SNAP-23 in macrophages. Our results clarify the regulatory mechanisms underlying intracellular transport of TLR4 and have implications for microbial pathogenesis and immune responses.

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