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2014 ; 15
(ä): 21
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Neutrophil-derived microparticles induce myeloperoxidase-mediated damage of
vascular endothelial cells
#MMPMID24915973
Pitanga TN
; de Aragão França L
; Rocha VC
; Meirelles T
; Borges VM
; Gonçalves MS
; Pontes-de-Carvalho LC
; Noronha-Dutra AA
; dos-Santos WL
BMC Cell Biol
2014[Jun]; 15
(ä): 21
PMID24915973
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BACKGROUND: Upon activation neutrophil releases microparticles - small plasma
membrane vesicles that contain cell surface proteins and cytoplasmic matter, with
biological activities. In this study we investigated the potential role of
myeloperoxidase in the endothelial cell injury caused by neutrophil-derived
microparticles. RESULTS: Microparticles were produced by activating human
neutrophils with a calcium ionophore and characterized by flow cytometry and
transmission and scanning electron microscopy. Myeloperoxidase activity was
measured by luminol-dependent chemiluminescence. Neutrophil
microparticles-induced injuries and morphological alterations in human umbilical
vein endothelial cells (HUVECs) were evaluated by microscopy and flow cytometry.
Neutrophil microparticles were characterized as structures bounded by lipid
bilayers and were less than 1 ?m in diameter. The microparticles also expressed
CD66b, CD62L and myeloperoxidase, which are all commonly expressed on the surface
of neutrophils, as well as exposition of phosphatidylserine. The activity of the
myeloperoxidase present on the microparticles was confirmed by hypochlorous acid
detection. This compound is only catalyzed by myeloperoxidase in the presence of
hydrogen peroxide and chloride ion. The addition of sodium azide or taurine
inhibited and reduced enzymatic activity, respectively. Exposure of HUVEC to
neutrophil microparticles induced a loss of cell membrane integrity and
morphological changes. The addition of sodium azide or myeloperoxidase-specific
inhibitor-I consistently reduced the injury to the endothelial cells. Taurine
addition reduced HUVEC morphological changes. CONCLUSIONS: We have demonstrated
the presence of active myeloperoxidase in neutrophil microparticles and that the
microparticle-associated myeloperoxidase cause injury to endothelial cells.
Hence, the microparticle-associated myeloperoxidase-hydrogen peroxide-chloride
system may contribute to widespread endothelial cell damage in conditions of
neutrophil activation as observed in vasculitis and sepsis.
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