The effect of verocytotoxin-1 on non-adherent human monocytes : binding characteristics, protein synthesis and induction of cytokine release

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Effects of verocytotoxin-1 on nonadherent human monocytes: Binding characteristics, protein synthesis, and induction of cytokine release

The epidemic form of the hemolytic uremic syndrome (HUS) has been associated with a verocytotoxin producing Escherichia coli infection. Endothelial cell damage of glomeruli and arterioles of the kidney plays a central role in the pathogenesis of HUS. A number of observations in vivo and in vitro indicate that inflammatory mediators contribute to this process. In this study we investigated the binding of 125I-verocytotoxin-1 (VT-1) to freshly isolated human nonadherent monocytes as well as the nature of the ligand to which VT-1 binds on monocytes. On the average, freshly isolated monocytes have 0.07 x 105 specific binding sites for 125I-VT-1 per cell. Preincubation of nonadherent monocytes with bacterial lipopolysaccharide (LPS) caused a 23- to 30-fold increase of specific binding sites for VT-1 as shown by Scatchard plot analysis. Thin-layer chromatography of extracted neutral glycolipids of the cells and subsequent binding of 125I-VT-1 showed that human monocytes bind VT-1 to a globotriaosylceramide (Gb3) species that is different from that found on endothelial cells, probably a short-chain fattyacyl Gb3 or an α-OH-Gb3. In addition, we evaluated the functional consequences of VT-1 binding to human monocytes by investigating the effects of VT-1 on the total protein synthesis and, specifically, the production of the cytokines interleukin-1β (IL-1β), tumor necrosis factor- α (TNF-α), IL-6, and IL-8. We observed that VT-1 did not inhibit overall protein synthesis, nor under basal conditions, neither after stimulation with LPS, in contrast to previous observations with endothelial cells. Furthermore, we found that VT-1 induces the synthesis of the cytokines IL- 1β, TNF-α, IL-6, and IL-8 in nonstimulated monocytes by a LPS-independent cell activation. The increase in the production of cytokines was parallelled by an increase in mRNA, as was demonstrated for IL-6 by reverse transcription-polymerase chain reaction. These data suggest that inflammatory mediators locally produced by VT-1-stimulated monocytes may contribute to the pathogenic mechanism of the HUS. Chemicals/CAS: Bacterial Toxins; globotriaosylceramide, 71965-57-6; Interleukin-1; Interleukin-6; Interleukin-8; Interleukins; Ligands; Lipopolysaccharides; Polytetrafluoroethylene, 9002-84-0; Shiga-Like Toxin I; Trihexosylceramides; Tumor Necrosis Factor-alph

Effect of Recombinant Ifn-Gamma (Rifn-Gamma) on the Mechanism of Human Macrophage Igg Fcri-Mediated Cytotoxicity - Rifn-Gamma Decreases Inhibition by Cytophilic Human-Igg and Changes the Cytolytic Mechanism

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Editorial: addiction studies at Trinity College Dublin

Plans for a special issue of Drugs: Education, Prevention and Policy based on the addiction studies component of what is now the School of Social Work and Social Policy at Trinity College Dublin were initially discussed and agreed during 2009, the 25th anniversary of the first cohort of students through Trinity’s Diploma in Addiction Studies. We had initially thought of holding a one-day conference to which we would invite Irish and international speakers but – with the support and encouragement of Professor Betsy Thom (Editor-in-Chief) – decided it might be more useful and less ephemeral to mark the anniversary by the production of a special issue of this journal. Therefore, the articles in this issue were commissioned from staff and former students with a view, first of all, to allowing us to reflect on the overall experience of teaching addiction studies here at Trinity and, second, to explore a number of themes which, between them, might add to our understanding of addiction policy and practice in contemporary Ireland. The themes covered here are not, of course, unique to Ireland and we trust that the articles will be of interest and relevance to readers in other countries