The novel role of peroxiredoxin-2 in red cell membrane protein homeostasis and senescence.

Peroxiredoxin-2 (Prx2), a typical two-cysteine peroxiredoxin, is the third most abundant protein in red cells. Although progress has been made in the functional characterization of Prx2, its role in red cell membrane protein homeostasis is still under investigation. Here, we studied Prx2-/- mouse red cells. The absence of Prx2 promotes (i) activation of the oxidative-induced Syk pathway; (ii) increased band 3 Tyr phosphorylation, with clustered band 3; and (iii) increased heat shock protein (HSP27 and HSP70) membrane translocation. This was associated with enhanced in vitro erythrophagocytosis of Prx2-/- red cells and reduced Prx2-/- red cell survival, indicating the possible role of Prx2 membrane recruitment in red cell aging and in the clearance of oxidized hemoglobin and damaged proteins through microparticles. Indeed, we observed an increased release of microparticles from Prx2-/- mouse red cells. The mass spectrometric analysis of erythroid microparticles found hemoglobin chains, membrane proteins, and HSPs. To test these findings, we treated Prx2-/- mice with antioxidants in vivo. We observed that N-acetylcysteine reduced (i) Syk activation, (ii) band 3 clusterization, (iii) HSP27 membrane association, and (iv) erythroid microparticle release, resulting in increased Prx2-/- mouse red cell survival. Thus, we propose that Prx2 may play a cytoprotective role in red cell membrane protein homeostasis and senescence

Performance Scores in General Practice: A Comparison between the Clinical versus Medication-Based Approach to Identify Target Populations

CONTEXT: From one country to another, the pay-for-performance mechanisms differ on one significant point: the identification of target populations, that is, populations which serve as a basis for calculating the indicators. The aim of this study was to compare clinical versus medication-based identification of populations of patients with diabetes and hypertension over the age of 50 (for men) or 60 (for women), and any consequences this may have on the calculation of P4P indicators. METHODS: A comparative, retrospective, observational study was carried out with clinical and prescription data from a panel of general practitioners (GPs), the Observatory of General Medicine (OMG) for the year 2007. Two indicators regarding the prescription for statins and aspirin in these populations were calculated. RESULTS: We analyzed data from 21.690 patients collected by 61 GPs via electronic medical files. Following the clinical-based approach, 2.278 patients were diabetic, 8,271 had hypertension and 1.539 had both against respectively 1.730, 8.511 and 1.304 following the medication-based approach (% agreement = 96%, kappa = 0.69). The main reasons for these differences were: forgetting to code the morbidities in the clinical approach, not taking into account the population of patients who were given life style and diet rules only or taking into account patients for whom morbidities other than hypertension could justify the use of antihypertensive drugs in the medication-based approach. The mean (confidence interval) per doctor was 33.7% (31.5-35.9) for statin indicator and 38.4% (35.4-41.4) for aspirin indicator when the target populations were identified on the basis of clinical criteria whereas they were 37.9% (36.3-39.4) and 43.8% (41.4-46.3) on the basis of treatment criteria. CONCLUSION: The two approaches yield very "similar" scores but these scores cover different realities and offer food for thought on the possible usage of these indicators in the framework of P4P programmes

A spiral scaffold underlies cytoadherent knobs in Plasmodium falciparum-infected erythrocytes

Much of the virulence of Plasmodium falciparum malaria is caused by cytoadherence of infected erythrocytes, which promotes parasite survival by preventing clearance in the spleen. Adherence is mediated by membrane protrusions known as knobs, whose formation depends on the parasite-derived, knob-associated histidine-rich protein (KAHRP). Knobs are required for cytoadherence under flow conditions, and they contain both KAHRP and the parasite-derived erythrocyte membrane protein PfEMP1. Using electron tomography, we have examined the three-dimensional structure of knobs in detergent-insoluble skeletons of P. falciparum 3D7 schizonts. We describe a highly organised knob skeleton composed of a spiral structure coated by an electron dense layer underlying the knob membrane. This knob skeleton is connected by multiple links to the erythrocyte cytoskeleton. We used immuno-electron microscopy to locate KAHRP in these structures. The arrangement of membrane proteins in the knobs, visualised by high resolution freeze fracture scanning electron microscopy, is distinct from that in the surrounding erythrocyte membrane, with a structure at the apex that likely represents the adhesion site. Thus, erythrocyte knobs in P. falciparum infection contain a highly organised skeleton structure underlying a specialised region of membrane. We propose that the spiral and dense coat organise the cytoadherence structures in the knob, and anchor them into the erythrocyte cytoskeleton. The high density of knobs and their extensive mechanical linkage suggest an explanation for the rigidification of the cytoskeleton in infected cells, and for the transmission to the cytoskeleton of shear forces experienced by adhering cells

Negative Regulation of Schistosoma japonicum Egg-Induced Liver Fibrosis by Natural Killer Cells

The role of natural killer (NK) cells in infection-induced liver fibrosis remains obscure. In this study, we elucidated the effect of NK cells on Schistosoma japonicum (S. japonicum) egg-induced liver fibrosis. Liver fibrosis was induced by infecting C57BL/6 mice with 18–20 cercariae of S. japonicum. Anti-ASGM1 antibody was used to deplete NK cells. Toll-like receptor 3 ligand, polyinosinic-polycytidylic acid (poly I∶C) was used to enhance the activation of NK cells. Results showed that NK cells were accumulated and activated after S. japonicum infection, as evidenced by the elevation of CD69 expression and IFN-γ production. Depletion of NK cells markedly enhanced S. japonicum egg-induced liver fibrosis. Administration of poly I∶C further activated NK cells to produce IFN-γ and attenuated S. japonicum egg-induced liver fibrosis. The observed protective effect of poly I∶C on liver fibrosis was diminished through depletion of NK cells. Disruption of IFN-γ gene enhanced liver fibrosis and partially abolished the suppression of liver fibrosis by poly I∶C. Moreover, expression of retinoic acid early inducible 1 (RAE 1), the NKG2D ligand, was detectable at high levels on activated hepatic stellate cells derived from S. japonicum-infected mice, which made them more susceptible to hepatic NK cell killing. In conclusion, our findings suggest that the activated NK cells in the liver after S. japonicum infection negatively regulate egg-induced liver fibrosis via producing IFN-γ, and killing activated stellate cells

Transparent sunlight-activated antifogging metamaterials

Counteracting surface fogging to maintain surface transparency is important for a variety of applications including eyewear, windows and displays. Energy-neutral, passive approaches predominantly rely on engineering the surface wettability, but suffer from non-uniformity, contaminant deposition and lack of robustness, all of which substantially degrade durability and performance. Here, guided by nucleation thermodynamics, we design a transparent, sunlight-activated, photothermal coating to inhibit fogging. The metamaterial coating contains a nanoscopically thin percolating gold layer and is most absorptive in the near-infrared range, where half of the sunlight energy resides, thus maintaining visible transparency. The photoinduced heating effect enables sustained and superior fog prevention (4-fold improvement) and removal (3-fold improvement) compared with uncoated samples, and overall impressive performance, indoors and outdoors, even under cloudy conditions. The extreme thinness (~10 nm) of the coating—which can be produced by standard, readily scalable fabrication processes—enables integration beneath other coatings, rendering it durable even on highly compliant substrates.ISSN:1748-3387ISSN:1748-339

Targeting surface voids to counter membrane disorders in lipointoxication-related diseases.

Saturated fatty acids (SFA), which are abundant in the so-called western diet, have been shown to efficiently incorporate within membrane phospholipids and therefore impact on organelle integrity and function in many cell types. In the present study, we have developed a yeast-based two-step assay and a virtual screening strategy to identify new drugs able to counter SFA-mediated lipointoxication. The compounds identified here were effective in relieving lipointoxication in mammalian β-cells, one of the main targets of SFA toxicity in humans. In vitro reconstitutions and molecular dynamics simulations on bilayers revealed that these molecules, albeit according to different mechanisms, can generate voids at the membrane surface. The resulting surface defects correlate with the recruitment of loose lipid packing or void-sensing proteins required for vesicular budding, a central cellular process that is precluded under SFA accumulation. Taken together, the results presented here point at modulation of surface voids as a central parameter to consider in order to counter the impacts of SFA on cell function.This article is freely available from the publisher's site. Click on the Additional Link above to access the full-text

Erythrocyte membrane changes of chorea-acanthocytosis are the result of altered Lyn kinase activity

Acanthocytic RBCs are a peculiar diagnostic feature of chorea-acanthocytosis (ChAc), a rare autosomal recessive neurodegenerative disorder. Although recent years have witnessed some progress in the molecular characterization of ChAc, the mechanism(s) responsible for generation of acanthocytes in ChAc is largely unknown. As the membrane protein composition of ChAc RBCs is similar to that of normal RBCs, we evaluated the tyrosine (Tyr)–phosphorylation profile of RBCs using comparative proteomics. Increased Tyr phosphorylation state of several membrane proteins, including band 3, β-spectrin, and adducin, was noted in ChAc RBCs. In particular, band 3 was highly phosphorylated on the Tyr-904 residue, a functional target of Lyn, but not on Tyr-8, a functional target of Syk. In ChAc RBCs, band 3 Tyr phosphorylation by Lyn was independent of the canonical Syk-mediated pathway. The ChAc-associated alterations in RBC membrane protein organization appear to be the result of increased Tyr phosphorylation leading to altered linkage of band 3 to the junctional complexes involved in anchoring the membrane to the cytoskeleton as supported by coimmunoprecipitation of β-adducin with band 3 only in ChAc RBC-membrane treated with the Lyn-inhibitor PP2. We propose this altered association between membrane skeleton and membrane proteins as novel mechanism in the generation of acanthocytes in ChAc

Soluble Egg Antigen-Stimulated T Helper Lymphocyte Apoptosis and Evidence for Cell Death Mediated by FasL(+) T and B Cells during Murine Schistosoma mansoni Infection

Granuloma formation around schistosomal eggs is induced by soluble egg antigens (SEA) and mediated by the activity of CD4(+) Th lymphocytes and their cytokines. Regulation of the inflammatory Th cell response during infection is still insufficiently understood. The hypothesis of this study was that activation-induced cell death (AICD) of CD4(+) T cells is involved in the immune inflammatory response. This study investigated the dynamics of splenic and granuloma CD4(+) Th cell apoptosis and Fas ligand (FasL) expression during the acute and chronic stages of murine schistosomal infection. Enhanced apoptosis of freshly isolated CD4(+) Th lymphocytes commenced after egg deposition and persisted during the peak and modulated phases of granuloma formation. After oviposition, CD4(+), CD8(+), and CD19(+) splenocytes and granuloma cells expressed elevated levels of FasL but FasL expression declined during the downmodulated stage of infection. In culture, SEA induced splenic and granuloma CD4(+) T-cell apoptosis and stimulated expression of FasL on splenic but not granuloma CD4(+) T cells, CD8(+) T cells, and CD19(+) B cells. SEA-stimulated splenocytes and granuloma cells preferentially lysed a Fas-transfected target cell line. Depletion of B cells from SEA-stimulated splenic cultures decreased CD4(+) T cell apoptosis. Coculture of purified splenic B cells with CD4(+) T cells and adoptive transfer of purified B cells indicated that antigen-stimulated B cells can kill CD4(+) Th cells. However, CD4(+) T cells were the dominant mediators of apoptosis in the granuloma. This study indicates that AICD is involved in the apoptosis of CD4(+) T cells during schistosomal infection