Oxidative stress generated by hemorrhagic shock recruits Toll-like receptor 4 to the plasma membrane in macrophages.
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.
Powers
Kinga A
KA
Department of Surgery, St. Michael's Hospital and University Health Network, Toronto, Ontario, Canada.
Szászi
Katalin
K
Khadaroo
Rachel G
RG
Tawadros
Patrick S
PS
Marshall
John C
JC
Kapus
András
A
Rotstein
Ori D
OD
D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology; D000818:Animals; D002478:Cells, Cultured; D002784:Cholesterol / Q000172:deficiency; D045142:Cross-Priming / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D031541:Fluorescence Resonance Energy Transfer; D006861:Hydrogen Peroxide / Q000494:pharmacology; D016676:Macrophages, Alveolar / Q000166:cytology* / Q000187:drug effects; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D053594:Myeloid Differentiation Factor 88; D018384:Oxidative Stress; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012771:Shock, Hemorrhagic / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D049128:Sphingolipid Activator Proteins / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C507780:Myd88 protein, mouse; C507781:Myd88 protein, rat; D053594:Myeloid Differentiation Factor 88; D049128:Sphingolipid Activator Proteins; D051197:Toll-Like Receptor 4; D002784:Cholesterol; D006861:Hydrogen Peroxide