Volume 11 Supplement 4
Oxidant-induced TLR4 translocation in murine macrophages is Src kinase dependent
© BioMed Central Ltd 2007
Published: 26 September 2007
Multiorgan failure is a major cause of late mortality following trauma. Oxidative stress generated during shock/resuscitation (S/R) contributes to tissue injury by priming the immune system for an exaggerated response to subsequent inflammatory stimuli such as lipopolysaccharide (LPS): the so-called 'two-hit hypothesis'. The mechanisms of oxidant-induced cell priming, however, remain poorly elucidated. Our group has previously reported a role in this priming process for translocation of the LPS receptor TLR4 to the plasma membrane . We have also previously shown that oxidant priming reprograms LPS signaling in macrophages to a Src-dependent pathway leading to PI3k activation . Taken together, we hypothesized that Src activation may play a role in oxidant-induced TLR4 translocation.
Materials and methods
Wild-type (WT) and triple Src (hck/fgr/lyn-/-) knockout (KO) mice were subjected to hemorrhagic shock and resuscitation to generate oxidative stress in vivo. Alveolar macrophages (AMs) were then retrieved by bronchoalveolar lavage and analyzed for TLR4 translocation by immunofluorescence staining and flow cytometry. In a separate in vitro experiment, AMs from WT and KO mice were exposed to 200 μM hydrogen peroxide for 60 minutes and similarly analyzed by flow cytometry for surface expression of TLR4.
Oxidative stress induces TLR4 translocation to the cell surface of macrophages in a Src-dependent manner. Since cellular responsiveness to LPS is known to correlate with surface levels of TLR4, this novel finding may direct future therapies in modulating oxidant-induced cellular priming and subsequent organ failure.
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