Increased neutrophil actin production and translocation of myeloperoxidase in patients with acetaminophen-induced acute liver failure may contribute to multiorgan failure

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Background: There is a marked propensity for patients with acetaminophen-induced acute liver failure (AALF) to develop bacterial and fungal infections which may not only hasten the development of brain edema, but also precipitate multiorgan failure (MOF) and death. Neutrophil dysfunction has recently been shown to be an important biomarker of poor prognosis in AALF. Myeloperoxidase (MPO) is abundantly expressed in neutrophil azurophilic granules and generates reactive oxygen species (ROS) which kill invading pathogens but during AALF also induce bystander damage and MOF. Actin, a cytoskeletal globular protein, plays a key role in neutrophil degranulation. Therefore we sought to determine the neutrophil spontaneous oxidative burst (SOB), MPO degranulation and actin produc-tion in AALF (n=11) compared to healthy controls (HC) (n=10). Methods: Neutrophil SOB was measured by the conversion of dihydrorhodamine to rhodamine by peroxidase. Leukocytes were stained with fluorochrome-bound anti-CD16/CD11b/MPO antibodies to determine the neutrophil extracellular (EC) and intracellular (IC) (after permeabilisation) changes following the addition of E. coli, by flow cytometry. Transmission elec-tron microscopy (TEM) was performed on isolated leukocytes from whole blood and stained with primary mouse (anti-actin and anti-MPO) antibodies independently and then with sec-ondary gold-conjugated antibodies. Stained sections were viewed using TEM and images were acquired with a digital camera. The gold particles present in the cells were counted using ImageJ software and relative labelling index (RLI) was calculated to determine the specificity of the stain (<1-random and non-specific labelling). Plasma cytokines were also mea-sured. Results: SOB was increased in AALF neutrophils com-pared to HC (p<0.0001). Baseline EC MPO was increased in AALF patients compared to HC (p<0.0001). Following E. coli stimulation, EC MPO was increased in HC compared to base-line (p<0.05) but not in AALF. There was no difference in the baseline or post stimulation IC MPO between AALF and HC. TEM revealed no difference in the MPO labelling in AALF com-pared to HC. However, actin was increased in the cytoplasm of neutrophils (RLI>1) in AALF compared to HC (p<0.005; degree of freedom 1). Plasma IL-6 and IL-8 were increased in AALF compared to HC (p<0.0001). Conclusion: These data show that there is no deficiency in the production of MPO in AALF. However the increase in neutrophil SOB, degranulation as measured by actin and EC MPO in AALF implies that gran-ules translocate to the cell surface releasing ROS into the tissues thereby contributing to bystander damage and organ failure.
Original languageEnglish
Article number738
Pages (from-to)558A-559A
Number of pages2
Publication statusPublished - 2014
Event65th Annual Meeting of the American-Association-for-the-Study-of-Liver-Diseases - Boston, MA, United Kingdom
Duration: 7 Nov 201411 Nov 2014


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