The influence of receptor-ligand interactions on gene expression and phagosome functions in mouse macrophages

Phagocytosis, the cellular uptake of particles and pathogens, is an essential function of the innate immune response. In this study, latex beads conjugated to immunoglobulin G, bacterial lipopolysaccharides, mannan or avidin were used to induce the internalization via different phagocytic receptors. Analysis of uptake and maturation of phagosomes, their proteomes as well as of macrophage gene expression during phagocytosis demonstrated that receptor-ligand interactions at the cell surface trigger a specfic signaling 'signature', which contributes to the intracellular fate of phagosomes

Titanium dioxide nanoparticles induce oxidative stress and DNA-adduct formation but not DNA-breakage in human lung cells

Titanium dioxide (TiO2), also known as titanium (IV) oxide or anatase, is the naturally occurring oxide of titanium. It is also one of the most commercially used form. To date, no parameter has been set for the average ambient air concentration of TiO2 nanoparticles (NP) by any regulatory agency. Previously conducted studies had established these nanoparticles to be mainly non-cyto- and -genotoxic, although they had been found to generate free radicals both acellularly (specially through photocatalytic activity) and intracellularly. The present study determines the role of TiO2-NP (anatase, ∅ < 100 nm) using several parameters such as cyto- and genotoxicity, DNA-adduct formation and generation of free radicals following its uptake by human lung cells in vitro. For comparison, iron containing nanoparticles (hematite, Fe2O3, ∅ < 100 nm) were used. The results of this study showed that both types of NP were located in the cytosol near the nucleus. No particles were found inside the nucleus, in mitochondria or ribosomes. Human lung fibroblasts (IMR-90) were more sensitive regarding cyto- and genotoxic effects caused by the NP than human bronchial epithelial cells (BEAS-2B). In contrast to hematite NP, TiO2-NP did not induce DNA-breakage measured by the Comet-assay in both cell types. Generation of reactive oxygen species (ROS) was measured acellularly (without any photocatalytic activity) as well as intracellularly for both types of particles, however, the iron-containing NP needed special reducing conditions before pronounced radical generation. A high level of DNA adduct formation (8-OHdG) was observed in IMR-90 cells exposed to TiO2-NP, but not in cells exposed to hematite NP. Our study demonstrates different modes of action for TiO2- and Fe2O3-NP. Whereas TiO2-NP were able to generate elevated amounts of free radicals, which induced indirect genotoxicity mainly by DNA-adduct formation, Fe2O3-NP were clastogenic (induction of DNA-breakage) and required reducing conditions for radical formation

Integrated network reconstruction, visualization and analysis using YANAsquare

<p>Abstract</p> <p>Background</p> <p>Modeling of metabolic networks includes tasks such as network assembly, network overview, calculation of metabolic fluxes and testing the robustness of the network.</p> <p>Results</p> <p>YANAsquare provides a software framework for rapid network assembly (flexible pathway browser with local or remote operation mode), network overview (visualization routine and YANAsquare editor) and network performance analysis (calculation of flux modes as well as target and robustness tests). YANAsquare comes as an easy-to-setup program package in Java. It is fully compatible and integrates the programs YANA (translation of gene expression values into flux distributions, metabolite network dissection) and Metatool (elementary mode calculation). As application examples we set-up and model the phospholipid network in the phagosome and genome-scale metabolic maps of <it>S.aureus</it>, <it>S.epidermidis </it>and <it>S.saprophyticus </it>as well as test their robustness against enzyme impairment.</p> <p>Conclusion</p> <p>YANAsquare is an application software for rapid setup, visualization and analysis of small, larger and genome-scale metabolic networks.</p

Aconitate decarboxylase 1 participates in the control of pulmonary Brucella infection in mice

Brucellosis is one of the most widespread bacterial zoonoses worldwide. Here, our aim was to identify the effector mechanisms controlling the early stages of intranasal infection with Brucella in C57BL/6 mice. During the first 48 hours of infection, alveolar macrophages (AMs) are the main cells infected in the lungs. Using RNA sequencing, we identified the aconitate decarboxylase 1 gene ( Acod1 ;also known as Immune responsive gene 1), as one of the genes most upregulated in murine AMs in response to B .melitensis infection at 24 hours post-infection. Upregulation of Acod1 was confirmed by RT-qPCR in lungs infected with B .melitensis and B .abortus .We observed that Acod1 -/- C57BL/6 mice display a higher bacterial load in their lungs than wild-type (wt) mice following B .melitensis or B .abortus infection, demonstrating that Acod1 participates in the control of pulmonary Brucella infection. The ACOD1 enzyme is mostly produced in mitochondria of macrophages, and converts cis-aconitate, a metabolite in the Krebs cycle, into itaconate. Dimethyl itaconate (DMI), a chemically-modified membrane permeable form of itaconate, has a dose-dependent inhibitory effect on Brucella growth in vitro .Interestingly, structural analysis suggests the binding of itaconate into the binding site of B .abortus isocitrate lyase. DMI does not inhibit multiplication of the isocitrate lyase deletion mutant Δ aceA B .abortus in vitro .Finally, we observed that, unlike the wt strain, the Δ aceA B .abortus strain multiplies similarly in wt and Acod1 -/- C57BL/6 mice. These data suggest that bacterial isocitrate lyase might be a target of itaconate in AMs.info:eu-repo/semantics/publishe

Intrinsic antibacterial activity of nanoparticles made of β-cyclodextrins potentiates their effect as drug nanocarriers against tuberculosis

Multi-drug-resistant tuberculosis (TB) is a major public health problem, concerning about half a million cases each year. Patients hardly adhere to the current strict treatment consisting of more than 10 000 tablets over a 2-year period. There is a clear need for efficient and better formulated medications. We have previously shown that nanoparticles made of cross-linked poly-β-cyclodextrins (pβCD) are efficient vehicles for pulmonary delivery of powerful combinations of anti-TB drugs. Here, we report that in addition to being efficient drug carriers, pβCD nanoparticles are endowed with intrinsic antibacterial properties. Empty pβCD nanoparticles are able to impair Mycobacterium tuberculosis (Mtb) establishment after pulmonary administration in mice. pβCD hamper colonization of macrophages by Mtb by interfering with lipid rafts, without inducing toxicity. Moreover, pβCD provoke macrophage apoptosis, leading to depletion of infected cells, thus creating a lung microenvironment detrimental to Mtb persistence. Taken together, our results suggest that pβCD nanoparticles loaded or not with antibiotics have an antibacterial action on their own and could be used as a carrier in drug regimen formulations effective against TB.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Patterns, receptors and signals:regulation of phagosome maturation

Recognition of microbial pathogens and dead cells and their phagocytic uptake by specialized immune cells are essential to maintain host homeostasis. Phagosomes undergo fusion and fission events with endosomal and lysosomal compartments, a process called 'phagosome maturation', which leads to the degradation of the phagosomal content. However, many phagocytic cells also act as antigen-presenting cells and must balance degradation and peptide preservation. Emerging evidence indicates that receptor engagement by phagosomal cargo, as well as inflammatory mediators and cellular activation affect many aspects of phagosome maturation. Unsurprisingly, pathogens have developed strategies to hijack this machinery, thereby interfering with host immunity. Here, we highlight progress in this field, summarize findings on the impact of immune signals, and discuss consequences for pathogen elimination

Infection and immunity : 'There Are Things Out There You (Don't) Need To Know About'

This Special Issue of The FEBS Journal consists of 20 reviews covering various aspects and new developments in 'Infection and Immunity'. The issue includes expert views on the role of different immune cell populations, on the regulation of innate and adaptive immune responses, and novel concepts in host defence and inflammatory signalling. Many reviews in this issue also highlight potential targets for future therapeutic interventions that aim to tackle inflammatory and immune responses in health and diseas

Proteomics of Mycobacterium Infection: Moving towards a Better Understanding of Pathogen-Driven Immunomodulation

Intracellular bacteria are responsible for many infectious diseases in humans and have developed diverse mechanisms to interfere with host defense pathways. In particular, intracellular vacuoles are an essential niche used by pathogens to alter cellular and organelle functions, which facilitate replication and survival. Mycobacterium tuberculosis (Mtb), the pathogen causing tuberculosis in humans, is not only able to modulate its intraphagosomal fate by blocking phagosome maturation but has also evolved strategies to successfully prevent clearance by immune cells and to establish long-term survival in the host. Mass spectrometry (MS)-based proteomics allows the identification and quantitative analysis of complex protein mixtures and is increasingly employed to investigate host–pathogen interactions. Major challenges are limited availability and purity of pathogen-containing compartments as well as the asymmetric ratio in protein abundance when comparing bacterial and host proteins during the infection. Recent advances in purification techniques and MS technology helped to overcome previous difficulties and enable the detailed proteomic characterization of infected host cells and their pathogen-containing vacuoles. Here, we summarize current findings of the proteomic analysis of Mycobacterium-infected host cells and highlight progress that has been made to study the protein composition of mycobacterial vacuoles. Current investigations focus on the pathogenicity during Mtb infection, which will allow to better understand pathogen-induced changes and immunomodulation of infected host cells. Consequently, future research in this field will have important implications on host response, pathogen survival, and persistence, induced adaptive immunity and metabolic changes of immune cells promoting the development of novel host-directed therapies in tuberculosis

A reporter cell line for the automated quantification of SARS-CoV-2 infection in living cells

International audienceThe SARS-CoV-2 pandemic and the urgent need for massive antiviral testing highlighted the lack of a good cell-based assay that allowed for a fast, automated screening of antivirals in high-throughput content with minimal handling requirements in a BSL-3 environment. The present paper describes the construction of a green fluorescent substrate that, upon cleavage by the SARS-CoV-2 main protease, re-localizes from the cytoplasm in non-infected cells to the nucleus in infected cells. The construction was stably expressed, together with a red fluorescent nuclear marker, in a highly susceptible clone derived from Vero-81 cells. With this fluorescent reporter cell line, named F1G-red, SARS-CoV-2 infection can be scored automatically in living cells by comparing the patterns of green and red fluorescence signals acquired by automated confocal microscopy in a 384-well plate format. We show the F1G-red system is sensitive to several SARS-CoV-2 variants of concern and that it can be used to assess antiviral activities of compounds in dose–response experiments. This high-throughput system will provide a reliable tool for antiviral screening against SARS-CoV-2