Powers KA, Szaszi K, Khadaroo RG, Tawadros PS, Marshall JC, Kapus A, Rotstein ODOxidative stress generated by hemorrhagic shock recruits Toll-like receptor 4 to the plasma membrane in macrophages. J Exp Med 203:1951-1961

Departments of Surgery, St. Michael's Hospital and University Health Network, and Department of Surgery, University of Toronto, Toronto, Ontario, M5G 2C1, Canada
Journal of Experimental Medicine (Impact Factor: 12.52). 09/2006; 203(8):1951-61. DOI: 10.1084/jem.20060943
Source: PubMed


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-beta-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.

Download full-text


Available from: Katalin Szaszi, Jul 24, 2014
1 Follower
45 Reads
  • Source
    • "TLRs can either be activated by microbial compounds or cellular debris in the context of IR injury [42, 45–47]. One of the most widely investigated pattern recognition molecules is TLR4 usually mediating inflammatory response to gram negative lipopolysaccharide particles (LPS); however, TLR4 activation is significantly enhanced by oxidative stress occurring during IR injury [59]. TAK-242, an inhibitor of TLR4, shows efficacy in reduction of IR injury in large animal trials [60] (Table 4). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The idea of protecting the heart from ischemic insult during heart surgery to allow elective cardiac arrest is as old as the idea of cardiac surgery itself. The current gold standard in clinical routine is a high potassium regimen added either to crystalloid or blood cardioplegic solutions inducing depolarized arrest. Ongoing patient demographic changes with increasingly older, comorbidly ill patients and increasing case complexity with increasingly structurally abnormal hearts as morphological correlate paired with evolutions in pediatric cardiac surgery allowing more complex procedures than ever before redefine requirements for cardioprotection. Many, in part adversarial, regimens to protect the myocardium from ischemic insults have entered clinical routine; however, functional recovery of the heart is still often impaired due to perfusion injury. Myocardial reperfusion damage is a key determinant of postoperative organ functional recovery, morbidity, and mortality in adult and pediatric patients. There is a discrepancy between what current protective strategies are capable of and what they are expected to do in a rapidly changing cardiac surgery community. An increased understanding of the molecular players of ischemia reperfusion injury offers potential seeds for new cardioprotective regimens and may further displace boundaries of what is technically feasible.
    BioMed Research International 09/2014; 2014:325725. DOI:10.1155/2014/325725 · 2.71 Impact Factor
  • Source
    • "It has also been shown that lipid raft formation is involved in cell activation induced by oxidized lipids[38], production of pro-inflammatory cytokines[39] and uptake of acetyl LDL[40]. The following results indicate that the interaction of CD36 and PAFR occurs within lipid raft domains of the BMDM membrane: a) Disruption of lipid rafts by treatment with MβCD reduced the oxLDL uptake and IL-10 production; b) oxLDL induced co-immunoprecipitation of PAFR and CD36 with the constitutive raft protein, flotillin-1[23] and colocalization of PAFR and CD36 with the lipid raft marker GM1-ganglioside[41]. Data presented by others have been shown that CD36 is recruited to lipid rafts in a ligand-dependent manner[22,42]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Macrophage interaction with oxidized low-density lipoprotein (oxLDL) leads to its differentiation into foam cells and cytokine production, contributing to atherosclerosis development. In a previous study, we showed that CD36 and the receptor for platelet-activating factor (PAFR) are required for oxLDL to activate gene transcription for cytokines and CD36. Here, we investigated the localization and physical interaction of CD36 and PAFR in macrophages stimulated with oxLDL. We found that blocking CD36 or PAFR decreases oxLDL uptake and IL-10 production. OxLDL induces IL-10 mRNA expression only in HEK293T expressing both receptors (PAFR and CD36). OxLDL does not induce IL-12 production. The lipid rafts disruption by treatment with βCD reduces the oxLDL uptake and IL-10 production. OxLDL induces co-immunoprecipitation of PAFR and CD36 with the constitutive raft protein flotillin-1, and colocalization with the lipid raft-marker GM1-ganglioside. Finally, we found colocalization of PAFR and CD36 in macrophages from human atherosclerotic plaques. Our results show that oxLDL induces the recruitment of PAFR and CD36 into the same lipid rafts, which is important for oxLDL uptake and IL-10 production. This study provided new insights into how oxLDL interact with macrophages and contributing to atherosclerosis development.
    PLoS ONE 10/2013; 8(10):e76893. DOI:10.1371/journal.pone.0076893 · 3.23 Impact Factor
  • Source
    • "One such pathway is the NFκB (nuclear factor kappa B) pathway, the most potent activator of innate immunity, which induces the expression of various proinflammatory cytokines [36, 37]. ROS also enhance the translocation of TLRs (Toll-like receptors) to lipid rafts, in which signaling molecules cluster to effectively activate downstream signals [38, 39]. TLR accumulation in lipid rafts enhances inflammatory signals through the NFκB and IRF3 (interferon regulatory transcription factor 3) pathways [39]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Keap1-Nrf2 system protects animals from oxidative and electrophilic stresses. Nrf2 is a transcription factor that induces the expression of genes essential for detoxifying reactive oxygen species (ROS) and cytotoxic electrophiles. Keap1 is a stress sensor protein that binds to and ubiquitinates Nrf2 under unstressed conditions, leading to the rapid proteasomal degradation of Nrf2. Upon exposure to stress, Keap1 is modified and inactivated, which allows Nrf2 to accumulate and activate the transcription of a battery of cytoprotective genes. Antioxidative and detoxification activities are important for many types of cells to avoid DNA damage and cell death. Accumulating lines of recent evidence suggest that Nrf2 is also required for the primary functions of myeloid cells, which include phagocytosis, inflammation regulation, and ROS generation for bactericidal activities. In fact, results from several mouse models have shown that Nrf2 expression in myeloid cells is required for the proper regulation of inflammation, antitumor immunity, and atherosclerosis. Moreover, several molecules generated upon inflammation activate Nrf2. Although ROS detoxification mediated by Nrf2 is assumed to be required for anti-inflammation, the entire picture of the Nrf2-mediated regulation of myeloid cell primary functions has yet to be elucidated. In this review, we describe the Nrf2 inducers characteristic of myeloid cells and the contributions of Nrf2 to diseases.
    Oxidative Medicine and Cellular Longevity 06/2013; 2013(2):529219. DOI:10.1155/2013/529219 · 3.36 Impact Factor
Show more