Bystander signals from low- and high-dose irradiated human primary fibroblasts and keratinocytes modulate the inflammatory response of peripheral blood mononuclear cells.

Irradiated cells can propagate signals to neighboring cells. Manifestations of these so-called bystander effects (BEs) are thought to be relatively more important after exposure to low- vs high-dose radiation and can be mediated via the release of secreted molecules, including inflammatory cytokines, from irradiated cells. Thus, BEs can potentially modify the inflammatory environment of irradiated cells. To determine whether these modifications could affect the functionality of bystander immune cells and their inflammatory response, we analyzed and compared the in vitro response of primary human fibroblasts and keratinocytes to low and high doses of radiation and assessed their ability to modulate the inflammatory activation of peripheral blood mononuclear cells (PBMCs). Only high-dose exposure resulted in either up- or down-regulation of selected inflammatory genes. In conditioned culture media transfer experiments, radiation-induced bystander signals elicited from irradiated fibroblasts and keratinocytes were found to modulate the transcription of inflammatory mediator genes in resting PBMCs, and after activation of PBMCs stimulated with lipopolysaccharide (LPS), a strong inflammatory agent. Radiation-induced BEs induced from skin cells can therefore act as a modifier of the inflammatory response of bystander immune cells and affect their functionality.

Influences of Nanoparticles Characteristics on the Cellular Responses: The Example of Iron Oxide and Macrophages.

Iron oxide nanoparticles/microparticles are widely present in a variety of environments, e.g., as a byproduct of steel and iron degradation, as, for example, in railway brakes (e.g., metro station) or in welding fumes. As all particulate material, these metallic nanoparticles are taken up by macrophages, a cell type playing a key role in the innate immune response, including pathogen removal phagocytosis, secretion of free radical species such as nitric oxide or by controlling inflammation via cytokine release. In this paper, we evaluated how macrophages functions were altered by two iron based particles of different size (100 nm and 20 nm). We showed that at high, but subtoxic concentrations (1 mg/mL, large nanoparticles induced stronger perturbations in macrophages functions such as phagocytic capacity (tested with fluorescent latex microspheres) and the ability to respond to bacterial endotoxin lipopolysaccharide stimulus (LPS) in secreting nitric oxide and pro-cytokines (e.g., Interleukin-6 (IL-6) and Tumor Necrosis Factor (TNF)). These stronger effects may correlate with an observed stronger uptake of iron for the larger nanoparticles.

A Combined N-terminomics and Shotgun Proteomics Approach to Investigate the Responses of Human Cells to Rapamycin and Zinc at the Mitochondrial Level.

All but thirteen mammalian mitochondrial proteins are encoded by the nuclear genome, translated in the cytosol and then imported into the mitochondria. For a significant proportion of the mitochondrial proteins, import is coupled with the cleavage of a presequence called the transit peptide, and the formation of a new N-terminus. Determination of the neo N-termini has been investigated by proteomic approaches in several systems, but generally in a static way to compile as many N-termini as possible. In the present study, we have investigated how the mitochondrial proteome and N-terminome react to chemical stimuli that alter mitochondrial metabolism, namely zinc ions and rapamycin. To this end, we have used a strategy that analyzes both internal and N-terminal peptides in a single run, the dN-TOP approach. We used these two very different stressors to sort out what could be a generic response to stress and what is specific to each of these stressors. Rapamycin and zinc induced different changes in the mitochondrial proteome. However, convergent changes to key mitochondrial enzymatic activities such as pyruvate dehydrogenase, succinate dehydrogenase and citrate synthase were observed for both treatments. Other convergent changes were seen in components of the N-terminal processing system and mitochondrial proteases. Investigations into the generation of neo-N-termini in mitochondria showed that the processing system is robust, as indicated by the lack of change in neo N-termini under the conditions tested. Detailed analysis of the data revealed that zinc caused a slight reduction in the efficiency of the N-terminal trimming system and that both treatments increased the degradation of mitochondrial proteins. In conclusion, the use of this combined strategy allowed a detailed analysis of the dynamics of the mitochondrial N-terminome in response to treatments which impact the mitochondria.

Utility of macrophages in an antitumor strategy based on the vectorization of iron oxide nanoparticles.

Many solid tumors and their metastases are still resistant to current cancer treatments such as chemo- and radiotherapy. The presence of a small population of Cancer Stem Cells in tumors is held responsible for relapses. Moreover, the various physical barriers of the organism (e.g. blood-brain barrier) prevent many drugs from reaching the target cells. In order to alleviate this constraint, we suggest a Trojan horse strategy consisting of intravascular injection of macrophages loaded with therapeutic nanoparticles (an iron nanoparticle-based solution marketed under the name of FERINJECT®) to bring a high quantity of the latter to the tumor. The aim of this article is to assess the response of primary macrophages to FERINJECT® via functional assays in order to ensure that the macrophages loaded with these nanoparticles are still relevant for our strategy. Following this first step, we demonstrate that the loaded macrophages injected into the bloodstream are able to migrate to the tumor site using small-animal imaging. Finally, using synchrotron radiation, we validate an improvement of the radiotherapeutic effect when FERINJECT®-laden macrophages are deposited at the vicinity of cancer cells and irradiated.

Differential proteomics highlights macrophage-specific responses to amorphous silica nanoparticles.

The technological and economic benefits of engineered nanomaterials may be offset by their adverse effects on living organisms. One of the highly produced nanomaterials under such scrutiny is amorphous silica nanoparticles, which are known to have an appreciable, although reversible, inflammatory potential. This is due to their selective toxicity toward macrophages, and it is thus important to study the cellular responses of this cell type to silica nanoparticles to better understand the direct or indirect adverse effects of nanosilica. We have here studied the responses of the RAW264.7 murine macrophage cells and of the control MPC11 plasma cells to subtoxic concentrations of nanosilica, using a combination of proteomic and targeted approaches. This allowed us to document alterations in the cellular cytoskeleton, in the phagocytic capacity of the cells as well as their ability to respond to bacterial stimuli. More surprisingly, silica nanoparticles also induce a greater sensitivity of macrophages to DNA alkylating agents, such as styrene oxide, even at doses which do not induce any appreciable cell death.

Culture medium associated changes in the core proteome of macrophages and in their responses to copper oxide nanoparticles.

The physiology of cells cultured in vitro depends obviously on the external conditions, including the nutrients present in the culture medium. In order to test the influence of this parameter, J774 macrophages grown either in RPMI or in DMEM were compared by a combination of targeted analyses and a proteomic approach. The two media differ in their glucose, amino acids, and vitamins concentrations, but there were no significant differences in the cell cycle or in the percentage of phagocytic cells in both media, although the phagocytic capacity (i.e. the number of phagocytized particles) was higher in DMEM. Conversely, we found that J774 cells grown in RPMI produced more nitric oxide in response to lipopolysaccharide. The proteomic study highlighted differences affecting the central metabolism and nucleotide metabolism, cytoskeleton, protein degradation, and cell signaling. Furthermore, proteomics showed that J774 cells grown in RPMI or in DMEM and exposed to copper oxide nanoparticles respond rather differently, with only a few proteins similarly modulated between cells grown in both media. Taken together, our results show that the basal state of cells grown in two different media is different, and this may affect the way they respond to an external stimulus or stress.

Different in vitro exposure regimens of murine primary macrophages to silver nanoparticles induce different fates of nanoparticles and different toxicological and functional consequences.

Silver nanoparticles (Ag-NPs) are used in a variety of consumers' goods. Their toxicological impact is currently intensely studied, mostly upon acute exposure, but their intracellular dissolution and fate is rather poorly documented. In this study, murine primary macrophages were exposed to a single high but non-lethal dose of Ag-NPs or to repeated, low doses of Ag-NPs. Cells were either collected immediately after acute exposure or after 72 h of recovery in the NP-free exposure medium. Ag intracellular content and distribution were analyzed by particle-induced X-ray emission, transmission electron microscopy coupled to energy-dispersive spectroscopy analysis and inductively coupled plasma mass spectrometry. In parallel, macrophage functionality as well as inflammatory and thiol-responses were assessed after Ag-NP exposure. We show that Ag accumulation in macrophages is similar upon acute and repeated exposure to Ag-NPs, and that Ag is partly expelled from cells during the 72 h recovery stage. However, acute exposure leads to a strong response of macrophages, characterized by reduced mitochondrial membrane potential, phagocytic capacity and nitric oxide (NO) production upon lipopolysaccharide (LPS) stimulation. Under this condition, we also show an increased release of proinflammatory cytokines as well as a decreased release of anti-inflammatory cytokines. This response is reversible since these biomarkers reach their basal level after the recovery phase; and is much less intense in repeatedly exposed cells. These results suggest that repeated exposure of macrophages to Ag-NPs, which is a more realistic exposure scenario than acute exposure, leads to significant Ag intracellular accumulation but a much less intense toxicological response.

A combined proteomic and targeted analysis unravels new toxic mechanisms for zinc oxide nanoparticles in macrophages.

The cellular responses of the J774 macrophage cell line to zinc oxide and zirconium oxide nanoparticles have been studied by a comparative quantitative, protein level based proteomic approach. The most prominent results have been validated by targeted approaches. These approaches have been carried out under culture conditions that stimulate mildly the aryl hydrocarbon receptor, thereby mimicking conditions that can be encountered in vivo in complex environments. The comparative approach with two nanoparticles allows to separate the common responses, which can be attributed to the phagocytosis event per se, from the response specific to each type of nanoparticles. The zinc-specific responses are the most prominent ones and include mitochondrial proteins too, but also signaling molecules such as MyD88, proteins associated with methylglyoxal detoxification (glyoxalase 2, aldose reductase) and deoxyribonucleotide hydrolases. The in cellulo inhibition of GAPDH by zinc was also documented, representing a possible source of methylglyoxal in the cells, leading to an increase in methylglyoxal-modified DNA bases. These observations may be mechanistically associated with the genotoxic effect of zinc and its selective effects on cancer cells. BIOLOGICAL SIGNIFICANCE: The responses of the murine J774 macrophage cell lines to two types of metallic oxide nanoparticles (zinc oxide and zirconium dioxide) were studied by a comparative 2D gel based approach. This allows sorting of shared responses from nanoparticle-specific responses. Zinc oxide nanoparticles induced specifically a strong decrease in the mitochondrial function, in phagocytosis and also an increase in the methylglyoxal-associated DNA damage, which may explain the well known genotoxicity of zinc. In conclusion, this study allows highlighting of pathways that may play an important role in the toxicity of the zinc oxide nanoparticles.

Comparative proteomic analysis of the molecular responses of mouse macrophages to titanium dioxide and copper oxide nanoparticles unravels some toxic mechanisms for copper oxide nanoparticles in macrophages.

Titanium dioxide and copper oxide nanoparticles are more and more widely used because of their catalytic properties, of their light absorbing properties (titanium dioxide) or of their biocidal properties (copper oxide), increasing the risk of adverse health effects. In this frame, the responses of mouse macrophages were studied. Both proteomic and targeted analyses were performed to investigate several parameters, such as phagocytic capacity, cytokine release, copper release, and response at sub toxic doses. Besides titanium dioxide and copper oxide nanoparticles, copper ions were used as controls. We also showed that the overall copper release in the cell does not explain per se the toxicity observed with copper oxide nanoparticles. In addition, both copper ion and copper oxide nanoparticles, but not titanium oxide, induced DNA strands breaks in macrophages. As to functional responses, the phagocytic capacity was not hampered by any of the treatments at non-toxic doses, while copper ion decreased the lipopolysaccharide-induced cytokine and nitric oxide productions. The proteomic analyses highlighted very few changes induced by titanium dioxide nanoparticles, but an induction of heme oxygenase, an increase of glutathione synthesis and a decrease of tetrahydrobiopterin in response to copper oxide nanoparticles. Subsequent targeted analyses demonstrated that the increase in glutathione biosynthesis and the induction of heme oxygenase (e.g. by lovastatin/monacolin K) are critical for macrophages to survive a copper challenge, and that the intermediates of the catecholamine pathway induce a strong cross toxicity with copper oxide nanoparticles and copper ions.

Analysis of cellular responses of macrophages to zinc ions and zinc oxide nanoparticles: a combined targeted and proteomic approach.

Two different zinc oxide nanoparticles, as well as zinc ions, are used to study the cellular responses of the RAW 264 macrophage cell line. A proteomic screen is used to provide a wide view of the molecular effects of zinc, and the most prominent results are cross-validated by targeted studies. Furthermore, the alteration of important macrophage functions (e.g. phagocytosis) by zinc is also investigated. The intracellular dissolution/uptake of zinc is also studied to further characterize zinc toxicity. Zinc oxide nanoparticles dissolve readily in the cells, leading to high intracellular zinc concentrations, mostly as protein-bound zinc. The proteomic screen reveals a rather weak response in the oxidative stress response pathway, but a strong response both in the central metabolism and in the proteasomal protein degradation pathway. Targeted experiments confirm that carbohydrate catabolism and proteasome are critical determinants of sensitivity to zinc, which also induces DNA damage. Conversely, glutathione levels and phagocytosis appear unaffected at moderately toxic zinc concentrations.

Molecular responses of mouse macrophages to copper and copper oxide nanoparticles inferred from proteomic analyses.

The molecular responses of macrophages to copper-based nanoparticles have been investigated via a combination of proteomic and biochemical approaches, using the RAW264.7 cell line as a model. Both metallic copper and copper oxide nanoparticles have been tested, with copper ion and zirconium oxide nanoparticles used as controls. Proteomic analysis highlighted changes in proteins implicated in oxidative stress responses (superoxide dismutases and peroxiredoxins), glutathione biosynthesis, the actomyosin cytoskeleton, and mitochondrial proteins (especially oxidative phosphorylation complex subunits). Validation studies employing functional analyses showed that the increases in glutathione biosynthesis and in mitochondrial complexes observed in the proteomic screen were critical to cell survival upon stress with copper-based nanoparticles; pharmacological inhibition of these two pathways enhanced cell vulnerability to copper-based nanoparticles, but not to copper ions. Furthermore, functional analyses using primary macrophages derived from bone marrow showed a decrease in reduced glutathione levels, a decrease in the mitochondrial transmembrane potential, and inhibition of phagocytosis and of lipopolysaccharide-induced nitric oxide production. However, only a fraction of these effects could be obtained with copper ions. In conclusion, this study showed that macrophage functions are significantly altered by copper-based nanoparticles. Also highlighted are the cellular pathways modulated by cells for survival and the exemplified cross-toxicities that can occur between copper-based nanoparticles and pharmacological agents.

Prion protein expression and functional importance in developmental angiogenesis: role in oxidative stress and copper homeostasis.

AIM: It has been convincingly shown that oxidative stress and toxicity by deregulated metals, such as copper (Cu), are tightly linked to the development of pre-eclampsia and intrauterine growth retardation (IUGR), the most threatening pathologies of human pregnancy. However, mechanisms implemented to control these effects are far from being understood. Among proteins that bind Cu and insure cellular protection against oxidative stress is the cellular prion protein (PrP(C)), a glycosyl phosphatidyl inositol-anchored glycoprotein, which we reported to be highly expressed in human placenta. Herein, we investigated the pathophysiological role of PrP(C) in Cu and oxidative stress homeostasis in vitro using human placenta and trophoblast cells, and in vivo using three strains of mice (C57Bl6, PrP(C) knockout mice [PrP(-/-)], and PrP(C) overexpressing mice [Tga20]). RESULTS: At the cellular level, PrP(C) protection against oxidative stress was established in multiple angiogenic processes: proliferation, migration, and tube-like organization. For the animal models, lack (PrP(-/-)) or overexpression (Tga20) of PrP(C) in gravid mice caused severe IUGR that was correlated with a decrease in litter size, changes in Cu homeostasis, increase in oxidative stress response, development of hypoxic environment, failure in placental function, and maintenance of growth defects of the offspring even 7.5 months after delivery. INNOVATION: PrP(C) could serve as a marker for the idiopathic IUGR disease. CONCLUSION: These findings demonstrate the stress-protective role of PrP(C) during development, and propose PrP(C) dysregulation as a novel causative element of IUGR.

Improvements and simplifications in in-gel fluorescent detection of proteins using ruthenium II tris-(bathophenanthroline disulfonate): the poor man's fluorescent detection method.

Fluorescent detection of proteins is a popular method of detection allying sensitivity, linearity and compatibility with mass spectrometry. Among the numerous methods described in the literature, staining with ruthenium II tris(bathophenanthroline disulfonate) is particularly cost-effective, but slightly cumbersome owing to difficulties in the preparation of the complex and complexity of staining protocols. We describe here the modifications on both aspects that allow to perform a higher contrast staining and offer a more robust method of complex preparation, thereby maximizing the advantages of the method.

Enhanced susceptibility of T lymphocytes to oxidative stress in the absence of the cellular prion protein.

The cellular prion glycoprotein (PrP(C)) is ubiquitously expressed but its physiologic functions remain enigmatic, particularly in the immune system. Here, we demonstrate in vitro and in vivo that PrP(C) is involved in T lymphocytes response to oxidative stress. By monitoring the intracellular level of reduced glutathione, we show that PrP(-/-) thymocytes display a higher susceptibility to H(2)O(2) exposure than PrP(+/+) cells. Furthermore, we find that in mice fed with a restricted diet, a regimen known to increase the intracellular level of ROS, PrP(-/-) thymocytes are more sensitive to oxidative stress. PrP(C) function appears to be specific for oxidative stress, since no significant differences are observed between PrP(-/-) and PrP(+/+) mice exposed to other kinds of stress. We also show a marked evolution of the redox status of T cells throughout differentiation in the thymus. Taken together, our results clearly ascribe to PrP(C) a protective function in thymocytes against oxidative stress.

Dual roles for MEF2A and MEF2D during human macrophage terminal differentiation and c-Jun expression.

Recent reports have evidenced a role for MEF2C (myocyte enhancer factor 2C) in myelopoiesis, although the precise functions of this transcription factor are still unclear. We show in the present study that MEF2A and MEF2D, two other MEF2 family members, are expressed in human primary monocytes and in higher amounts in monocyte-derived macrophages. High levels of MEF2A-MEF2D heterodimers are found in macrophage-differentiated HL60 cells. Chromatin immunoprecipitations demonstrate that MEF2A is present on the c-Jun promoter, both in undifferentiated and in macrophage-differentiated cells. Moreover, c-Jun expression is derepressed in undifferentiated cells in the presence of HDAC (histone deacetylase) inhibitor, indicating the importance of chromatin acetylation in this process. We show that MEF2A/D dimers strongly interact with HDAC1, and to a lesser extent with HDAC7 in macrophages, whereas low levels of MEF2A/D-HDAC1 complexes are found in undifferentiated cells or in monocytes. Since trichostatin A does not disrupt MEF2A/D-HDAC1 complexes, we analysed the potential interaction of MEF2A with p300 histone acetyltransferase, whose expression is up-regulated in macrophages. Interestingly, endogenous p300 only associates with MEF2A in differentiated macrophages, indicating that MEF2A/D could activate c-Jun expression in macrophages through a MEF2A/D-p300 activator complex. The targets of MEF2A/D-HDAC1-HDAC7 multimers remain to be identified. Nevertheless, these data highlight for the first time the possible dual roles of MEF2A and MEF2D in human macrophages, as activators or as repressors of gene transcription.

Overexpression of cellular prion protein induces an antioxidant environment altering T cell development in the thymus.

Cellular prion protein (PrP(C)) is an ubiquitously expressed glycoprotein whose roles are still widely discussed, particularly in the field of immunology. Using TgA20- and Tg33-transgenic mice overexpressing PrP(C), we investigated the consequences of this overexpression on T cell development. In both models, overexpression of PrP(C) induces strong alterations at different steps of T cell maturation. On TgA20 mice, we observed that these alterations are cell autonomous and lead to a decrease of alphabeta T cells and a concomitant increase of gammadelta T cell numbers. PrP(C) has been shown to bind and chelate copper and, interestingly, under a copper supplementation diet, TgA20 mice presented a partial restoration of the alphabeta T cell development, suggesting that PrP(C) overexpression, by chelating copper, generates an antioxidant context differentially impacting on alphabeta and gammadelta T cell lineage.

Quantitative and qualitative changes in V-J alpha rearrangements during mouse thymocytes differentiation: implication for a limited T cell receptor alpha chain repertoire.

Knowledge of the complete nucleotide sequence of the mouse TCRAD locus allows an accurate determination V-J rearrangement status. Using multiplex genomic PCR assays and real time PCR analysis, we report a comprehensive and systematic analysis of the V-J recombination of TCR alpha chain in normal mouse thymocytes during development. These respective qualitative and quantitative approaches give rise to four major points describing the control of gene rearrangements. (a) The V-J recombination pattern is not random during ontogeny and generates a limited TCR alpha repertoire; (b) V-J rearrangement control is intrinsic to the thymus; (c) each V gene rearranges to a set of contiguous J segments with a gaussian-like frequency; (d) there are more rearrangements involving V genes at the 3' side than 5' end of V region. Taken together, this reflects a preferential association of V and J gene segments according to their respective positions in the locus, indicating that accessibility of both V and J regions is coordinately regulated, but in different ways. These results provide a new insight into TCR alpha repertoire size and suggest a scenario for V usage during differentiation.