Publications by authors named "Pedro Escoll"

25 Publications

  • Page 1 of 1

Dichotomous metabolic networks govern human ILC2 proliferation and function.

Nat Immunol 2021 11 22;22(11):1367-1374. Epub 2021 Oct 22.

Innate Immunity Unit, Institut Pasteur, Inserm U1223, Paris, France.

Group 2 innate lymphoid cells (ILC2s) represent innate homologs of type 2 helper T cells (T2) that participate in immune defense and tissue homeostasis through production of type 2 cytokines. While T lymphocytes metabolically adapt to microenvironmental changes, knowledge of human ILC2 metabolism is limited, and its key regulators are unknown. Here, we show that circulating 'naive' ILC2s have an unexpected metabolic profile with a higher level of oxidative phosphorylation (OXPHOS) than natural killer (NK) cells. Accordingly, ILC2s are severely reduced in individuals with mitochondrial disease (MD) and impaired OXPHOS. Metabolomic and nutrient receptor analysis revealed ILC2 uptake of amino acids to sustain OXPHOS at steady state. Following activation with interleukin-33 (IL-33), ILC2s became highly proliferative, relying on glycolysis and mammalian target of rapamycin (mTOR) to produce IL-13 while continuing to fuel OXPHOS with amino acids to maintain cellular fitness and proliferation. Our results suggest that proliferation and function are metabolically uncoupled in human ILC2s, offering new strategies to target ILC2s in disease settings.
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http://dx.doi.org/10.1038/s41590-021-01043-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8553616PMC
November 2021

Polarized mitochondria as guardians of NK cell fitness.

Blood Adv 2021 01;5(1):26-38

INSERM U1223, Paris, France.

Distinct metabolic demands accompany lymphocyte differentiation into short-lived effector and long-lived memory cells. How bioenergetics processes are structured in innate natural killer (NK) cells remains unclear. We demonstrate that circulating human CD56Dim (NKDim) cells have fused mitochondria and enhanced metabolism compared with CD56Br (NKBr) cells. Upon activation, these 2 subsets showed a dichotomous response, with further mitochondrial potentiation in NKBr cells vs paradoxical mitochondrial fission and depolarization in NKDim cells. The latter effect impaired interferon-γ production, but rescue was possible by inhibiting mitochondrial fragmentation, implicating mitochondrial polarization as a central regulator of NK cell function. NKDim cells are heterogeneous, and mitochondrial polarization was associated with enhanced survival and function in mature NKDim cells, including memory-like human cytomegalovirus-dependent CD57+NKG2C+ subsets. In contrast, patients with genetic defects in mitochondrial fusion had a deficiency in adaptive NK cells, which had poor survival in culture. These results support mitochondrial polarization as a central regulator of mature NK cell fitness.
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http://dx.doi.org/10.1182/bloodadvances.2020003458DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7805327PMC
January 2021

Danger-associated metabolic modifications during bacterial infection of macrophages.

Int Immunol 2020 06;32(7):475-483

Institut Pasteur, Unité de Biologie des Bactéries Intracellulaires, Paris, France.

In this review, we propose that certain modifications in cellular metabolism might function as danger signals triggering inflammasome-mediated immune responses. We propose to call them danger-associated metabolic modifications (DAMMs). As intracellular bacteria can actively modulate macrophage metabolism for their benefit, infected host cells might sense bacteria-induced metabolic alterations and activate immune reactions. Here we report the known metabolic interactions that occur during infection of macrophages by intracellular bacteria and discuss the possible emergence of DAMMs upon bacteria-induced alterations of cellular metabolism.
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http://dx.doi.org/10.1093/intimm/dxaa035DOI Listing
June 2020

Legionnaires' Disease: State of the Art Knowledge of Pathogenesis Mechanisms of .

Annu Rev Pathol 2020 01 28;15:439-466. Epub 2019 Oct 28.

Institut Pasteur, Biologie des Bactéries Intracellulaires, CNRS UMR 3525, 75015 Paris, France; email:

species are environmental gram-negative bacteria able to cause a severe form of pneumonia in humans known as Legionnaires' disease. Since the identification of in 1977, four decades of research on biology and Legionnaires' disease have brought important insights into the biology of the bacteria and the molecular mechanisms that these intracellular pathogens use to cause disease in humans. Nowadays, species constitute a remarkable model of bacterial adaptation, with a genus genome shaped by their close coevolution with amoebae and an ability to exploit many hosts and signaling pathways through the secretion of a myriad of effector proteins, many of which have a eukaryotic origin. This review aims to discuss current knowledge of infection mechanisms and future research directions to be taken that might answer the many remaining open questions. This research will without a doubt be a terrific scientific journey worth taking.
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http://dx.doi.org/10.1146/annurev-pathmechdis-012419-032742DOI Listing
January 2020

Metabolic reprogramming: an innate cellular defence mechanism against intracellular bacteria?

Curr Opin Immunol 2019 10 24;60:117-123. Epub 2019 Jun 24.

Institut Pasteur, Biologie des Bactéries Intracellulaires, UMR 3525, CNRS, Paris, France. Electronic address:

The limited metabolic resources of a cell represent an intriguing 'conflict of interest' during host-pathogen interactions, as the battle for nutrients might determine the outcome of an infection. To adapt their metabolic needs, innate immune cells such as monocytes, macrophages or dendritic cells reprogram their metabolism upon activation by microbial compounds. In turn, infection by intracellular bacteria provokes metabolic alterations of the host cell that benefit the pathogen. Here, we discuss the state-of-the-art knowledge on metabolic reprogramming of host cells upon activation or infection with intracellular bacteria. The study of the host-driven and pathogen-driven metabolic alterations that seem to co-exist during infection is an emerging field that will define the metabolic pathways that might be targeted to combat infection.
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http://dx.doi.org/10.1016/j.coi.2019.05.009DOI Listing
October 2019

Mitochondrial Dynamics and Activity in Legionella-Infected Cells.

Methods Mol Biol 2019 ;1921:205-220

Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France.

The study of Legionella pneumophila interactions with host mitochondria during infection has been historically limited by the techniques available to analyze and quantify mitochondrial dynamics and activity in living cells. Recently, new, powerful techniques such as high-content microscopy or mitochondrial respiration assays (Seahorse) have been developed to quantitatively analyze mitochondrial parameters. Here we present state-of-the-art methods adapted to analyze mitochondrial dynamics and activity during Legionella infection of living human primary macrophages.
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http://dx.doi.org/10.1007/978-1-4939-9048-1_13DOI Listing
June 2019

Metabolic reprogramming of host cells upon bacterial infection: Why shift to a Warburg-like metabolism?

FEBS J 2018 06 14;285(12):2146-2160. Epub 2018 Apr 14.

Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France.

The finding that the Warburg effect observed in proliferating cancer cells is also observed during immune responses renewed the interest in the study of metabolic reprogramming of immune cells, a field of investigation called immunometabolism. However, the specific mechanisms and processes underlying metabolic changes of host cells upon bacterial infection remain poorly understood. Several recent reports have reported that mammalian cells infected with intracellular bacteria have an altered metabolism that resembles the Warburg effect seen in cancer cells. In this Review, we will summarize current knowledge on metabolic reprogramming and discuss putative causes underlying the preferential remodelling of host cells to Warburg-like metabolic programs during infection by intracellular bacteria.
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http://dx.doi.org/10.1111/febs.14446DOI Listing
June 2018

CsrA regulates a metabolic switch from amino acid to glycerolipid metabolism.

Open Biol 2017 11;7(11)

Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France

CsrA plays a crucial role in the life-stage-specific expression of virulence phenotypes and metabolic activity. However, its exact role is only partly known. To elucidate how CsrA impacts metabolism we analysed the CsrA depended regulation of metabolic functions by comparative C-isotopologue profiling and oxygen consumption experiments of a wild-type (wt) strain and its isogenic mutant. We show that a mutant has significantly lower respiration rates when serine, alanine, pyruvate, α-ketoglutarate or palmitate is the sole carbon source. By contrast, when grown in glucose or glycerol, no differences in respiration were detected. Isotopologue profiling uncovered that the transfer of label from [U-C]serine via pyruvate into the citrate cycle and gluconeogenesis was lower in the mutant as judged from the labelling patterns of protein-derived amino acids, cell-wall-derived diaminopimelate, sugars and amino sugars and 3-hydroxybutyrate derived from polyhydroxybutyrate (PHB). Similarly, the incorporation of [U-C]glucose via the glycolysis/Entner-Doudoroff (ED) pathway but not via the pentose phosphate pathway was repressed in the mutant. On the other hand, fluxes due to [U-C]glycerol utilization were increased in the mutant. In addition, we showed that exogenous [1,2,3,4-C]palmitic acid is efficiently used for PHB synthesis via C-acetyl-CoA. Taken together, CsrA induces serine catabolism via the tricarboxylic acid cycle and glucose degradation via the ED pathway, but represses glycerol metabolism, fatty acid degradation and PHB biosynthesis, in particular during exponential growth. Thus, CsrA has a determining role in substrate usage and carbon partitioning during the life cycle and regulates a switch from amino acid usage in replicative phase to glycerolipid usage during transmissive growth.
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http://dx.doi.org/10.1098/rsob.170149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717341PMC
November 2017

Manipulation of Autophagy by Bacterial Pathogens Impacts Host Immunity.

Curr Issues Mol Biol 2018 6;25:81-98. Epub 2017 Sep 6.

Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France, and CNRS UMR 3525, Paris, France.

Autophagy is a highly conserved catabolic process, degrading unnecessary or damaged components in the eukaryotic cell to maintain cellular homeostasis, but it is also an intrinsic cellular defence mechanism to remove invading pathogens. A crosstalk between autophagy and innate or adaptive immune responses has been recently reported, whereby autophagy influences both, innate and adaptive immunity like the production and secretion of pro-inflammatory cytokines or MHC class II antigen presentation to T cells. Pathogenic bacteria have evolved diverse strategies to manipulate autophagy, mechanisms that also impact host immune responses at different levels. Here we discuss the influence of autophagy on self-autonomous, innate and adaptive immunity and then focus on how bacterial mechanisms that shape autophagy may impact the host immune system.
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http://dx.doi.org/10.21775/cimb.025.081DOI Listing
August 2018

Legionella pneumophila Modulates Mitochondrial Dynamics to Trigger Metabolic Repurposing of Infected Macrophages.

Cell Host Microbe 2017 Sep 31;22(3):302-316.e7. Epub 2017 Aug 31.

Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris 75724, France; CNRS UMR 3525, Paris 75724, France. Electronic address:

The intracellular bacteria Legionella pneumophila encodes a type IV secretion system (T4SS) that injects effector proteins into macrophages in order to establish and replicate within the Legionella-containing vacuole (LCV). Once generated, the LCV interacts with mitochondria through unclear mechanisms. We show that Legionella uses both T4SS-independent and T4SS-dependent mechanisms to respectively interact with mitochondria and induce mitochondrial fragmentation that ultimately alters mitochondrial metabolism. The T4SS effector MitF, a Ran GTPase activator, is required for fission of the mitochondrial network. These effects of MitF occur through accumulation of mitochondrial DNM1L, a GTPase critical for fission. Furthermore mitochondrial respiration is abruptly halted in a T4SS-dependent manner, while T4SS-independent upregulation of cellular glycolysis remains elevated. Collectively, these alterations in mitochondrial dynamics promote a Warburg-like phenotype in macrophages that favors bacterial replication. Hence the rewiring of cellular bioenergetics to create a replication permissive niche in host cells is a virulence strategy of L. pneumophila.
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http://dx.doi.org/10.1016/j.chom.2017.07.020DOI Listing
September 2017

MAMs are attractive targets for bacterial repurposing of the host cell: MAM-functions might be key for undermining an infected cell.

Bioessays 2017 02 27;39(2). Epub 2016 Dec 27.

Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France.

Pathogenic bacteria frequently target the endoplasmic reticulum (ER) and mitochondria in order to exploit host functions. ER-mitochondria inter-organelle communication is topologically sub-compartmentalized at mitochondria-associated ER membranes (MAMs). MAMs are specific membranous microdomains with unique regulatory functions such as lipid synthesis and trafficking, calcium homeostasis, mitochondrial morphology, inflammasome activation, autophagosome formation, and apoptosis. These important cellular processes are all modulated by pathogens to subvert host functions and promote infection, thus it is tempting to assume that pathogenic bacteria target MAMs to subvert these different pathways in their hosts. First lines of evidence that support this hypothesis come from Legionella pneumophila. This intracellular bacterium secretes an effector that exhibits sphingosine-1 phosphate lyase activity (LpSpl) that seems to target MAMs to modulate the autophagy response to infection. Here we thus propose the concept that MAMs could be targeted by pathogenic bacteria to undermine key host cellular processes.
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http://dx.doi.org/10.1002/bies.201600171DOI Listing
February 2017

Legionella longbeachae Is Immunologically Silent and Highly Virulent In Vivo.

J Infect Dis 2017 Feb;215(3):440-451

Department of Cell Biology.

Background: Legionella longbeachae (Llo) and Legionella pneumophila (Lpn) are the most common pneumonia-causing agents of the genus. Although both species can be lethal to humans and are highly prevalent, little is known about the molecular pathogenesis of Llo infections. In murine models of infection, Lpn infection is self-limited, whereas Llo infection is lethal.

Methods: We used mouse macrophages, human macrophages, human epithelial cells, and mouse infections in vivo to evaluate multiple parameters of the infection.

Results: We determined that the Llo Dot/Icm secretion system is critical for virulence. Different than Lpn, Llo disseminates and the animals develop a severe pulmonary failure, as demonstrated by lung mechanics and blood oxygenation assays. As compared to Lpn, Llo is immunologically silent and fails to trigger the production of cytokines in human pulmonary epithelial cells and in mouse and human macrophages. Infections in Tnfr1-/-, Ifng-/-, and Il12p40-/- mice supported the participation of cytokines for the resistance phenotype.

Conclusions: Both Lpn and Llo require the Dot/Icm system for pathogenesis, but the infection outcome is strikingly different. Llo is immunologically silent, highly virulent, and lethal. The differences reported herein may reflect unappreciated clinical differences in patients infected with Lpn or Llo.
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http://dx.doi.org/10.1093/infdis/jiw560DOI Listing
February 2017

Legionella pneumophila restrains autophagy by modulating the host's sphingolipid metabolism.

Autophagy 2016 06 18;12(6):1053-4. Epub 2016 May 18.

a Institut Pasteur , Biologie des Bactéries Intracellulaires , Paris , France.

Sphingolipids are bioactive molecules playing a key role as membrane components, but they are also central regulators of many intracellular processes including macroautophagy/autophagy. In particular, sphingosine-1-phosphate (S1P) is a critical mediator that controls the balance between sphingolipid-induced autophagy and cell death. S1P levels are adjusted via S1P synthesis, dephosphorylation or degradation, catalyzed by SGPL1 (sphingosine-1-phosphate lyase 1). Intracellular pathogens are able to modulate many different host cell pathways to allow their replication. We have found that infection of eukaryotic cells with the human pathogen Legionella pneumophila triggers a change in the host cell sphingolipid metabolism and specifically affects the levels of sphingosine. Indeed, L. pneumophila secretes a protein highly homologous to eukaryotic SGPL1 (named LpSPL). We solved the crystal structure of LpSPL and showed that it encodes lyase activity, targets the host's sphingolipid metabolism, and plays a role in starvation-induced autophagy during L. pneumophila infection to promote intracellular survival.
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http://dx.doi.org/10.1080/15548627.2016.1166325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4922430PMC
June 2016

Modulation of Host Autophagy during Bacterial Infection: Sabotaging Host Munitions for Pathogen Nutrition.

Front Immunol 2016 3;7:81. Epub 2016 Mar 3.

Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France; CNRS UMR 3525, Paris, France.

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http://dx.doi.org/10.3389/fimmu.2016.00081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4776121PMC
March 2016

Legionella pneumophila S1P-lyase targets host sphingolipid metabolism and restrains autophagy.

Proc Natl Acad Sci U S A 2016 Feb 1;113(7):1901-6. Epub 2016 Feb 1.

Institut Pasteur, Biologie des Bactéries Intracellulaires, 75724 Paris, France; CNRS UMR 3525, 75724 Paris, France;

Autophagy is an essential component of innate immunity, enabling the detection and elimination of intracellular pathogens. Legionella pneumophila, an intracellular pathogen that can cause a severe pneumonia in humans, is able to modulate autophagy through the action of effector proteins that are translocated into the host cell by the pathogen's Dot/Icm type IV secretion system. Many of these effectors share structural and sequence similarity with eukaryotic proteins. Indeed, phylogenetic analyses have indicated their acquisition by horizontal gene transfer from a eukaryotic host. Here we report that L. pneumophila translocates the effector protein sphingosine-1 phosphate lyase (LpSpl) to target the host sphingosine biosynthesis and to curtail autophagy. Our structural characterization of LpSpl and its comparison with human SPL reveals high structural conservation, thus supporting prior phylogenetic analysis. We show that LpSpl possesses S1P lyase activity that was abrogated by mutation of the catalytic site residues. L. pneumophila triggers the reduction of several sphingolipids critical for macrophage function in an LpSpl-dependent and -independent manner. LpSpl activity alone was sufficient to prevent an increase in sphingosine levels in infected host cells and to inhibit autophagy during macrophage infection. LpSpl was required for efficient infection of A/J mice, highlighting an important virulence role for this effector. Thus, we have uncovered a previously unidentified mechanism used by intracellular pathogens to inhibit autophagy, namely the disruption of host sphingolipid biosynthesis.
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http://dx.doi.org/10.1073/pnas.1522067113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763766PMC
February 2016

Targeting of host organelles by pathogenic bacteria: a sophisticated subversion strategy.

Nat Rev Microbiol 2016 Jan 23;14(1):5-19. Epub 2015 Nov 23.

Biologie des Bactéries Intracellulaires, Centre National de la Recherche Scientifique UMR 3525, Institut Pasteur, Biologie des 28 rue du Dr. Roux, 75724 Paris Cedex 15, France.

Many bacterial pathogens have evolved the ability to subvert and exploit host functions in order to enter and replicate in eukaryotic cells. For example, bacteria have developed specific mechanisms to target eukaryotic organelles such as the nucleus, the mitochondria, the endoplasmic reticulum and the Golgi apparatus. In this Review, we highlight the most recent advances in our understanding of the mechanisms that bacterial pathogens use to target these organelles. We also discuss how these strategies allow bacteria to manipulate host functions and to ultimately enable bacterial infection.
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http://dx.doi.org/10.1038/nrmicro.2015.1DOI Listing
January 2016

Sustained interleukin-1β exposure modulates multiple steps in glucocorticoid receptor signaling, promoting split-resistance to the transactivation of prominent anti-inflammatory genes by glucocorticoids.

Mediators Inflamm 2015 22;2015:347965. Epub 2015 Apr 22.

Immunology and Individualized Medicine, IMMPA CSIC/UAH Joint Unit, Alcalá de Henares, 28805 Madrid, Spain.

Clinical treatment with glucocorticoids (GC) can be complicated by cytokine-induced glucocorticoid low-responsiveness (GC-resistance, GCR), a condition associated with a homogeneous reduction in the expression of GC-receptor- (GR-) driven anti-inflammatory genes. However, GR level and phosphorylation changes modify the expression of individual GR-responsive genes differently. As sustained IL-1β exposure is key in the pathogenesis of several major diseases with prevalent GCR, we examined GR signaling and the mRNA expression of six GR-driven genes in cells cultured in IL-1β and afterwards challenged with GC. After a GC challenge, sustained IL-1β exposure reduced the cytoplasmic GR level, GR(Ser203) and GR(Ser211) phosphorylation, and GR nuclear translocation and led to selective GCR in the expression of the studied genes. Compared to GC alone, in a broad range of GC doses plus sustained IL-1β, FKBP51 mRNA expression was reduced by 1/3, TTP by 2/3, and IRF8 was completely knocked down. In contrast, high GC doses did not change the expression of GILZ and DUSP1, while IGFBP1 was increased by 5-fold. These effects were cytokine-selective, IL-1β dose- and IL-1R1-dependent. The integrated gain and loss of gene functions in the "split GCR" model may provide target cells with a survival advantage by conferring resistance to apoptosis, chemotherapy, and GC.
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http://dx.doi.org/10.1155/2015/347965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4421076PMC
February 2016

TLR9 activation is triggered by the excess of stimulatory versus inhibitory motifs present in Trypanosomatidae DNA.

PLoS Negl Trop Dis 2014 Nov 13;8(11):e3308. Epub 2014 Nov 13.

Institut Pasteur, Département Infection et Epidémiologie, Unité Cytokines & Inflammation, Paris, France.

DNA sequences purified from distinct organisms, e.g. non vertebrate versus vertebrate ones, were shown to differ in their TLR9 signalling properties especially when either mouse bone marrow-derived- or human dendritic cells (DCs) are probed as target cells. Here we found that the DC-targeting immunostimulatory property of Leishmania major DNA is shared by other Trypanosomatidae DNA, suggesting that this is a general trait of these eukaryotic single-celled parasites. We first documented, in vitro, that the low level of immunostimulatory activity by vertebrate DNA is not due to its limited access to DCs' TLR9. In addition, vertebrate DNA inhibits the activation induced by the parasite DNA. This inhibition could result from the presence of competing elements for TLR9 activation and suggests that DNA from different species can be discriminated by mouse and human DCs. Second, using computational analysis of genomic DNA sequences, it was possible to detect the presence of over-represented inhibitory and under-represented stimulatory sequences in the vertebrate genomes, whereas L. major genome displays the opposite trend. Interestingly, this contrasting features between L. major and vertebrate genomes in the frequency of these motifs are shared by other Trypanosomatidae genomes (Trypanosoma cruzi, brucei and vivax). We also addressed the possibility that proteins expressed in DCs could interact with DNA and promote TLR9 activation. We found that TLR9 is specifically activated with L. major HMGB1-bound DNA and that HMGB1 preferentially binds to L. major compared to mouse DNA. Our results highlight that both DNA sequence and vertebrate DNA-binding proteins, such as the mouse HMGB1, allow the TLR9-signaling to be initiated and achieved by Trypanosomatidae DNA.
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http://dx.doi.org/10.1371/journal.pntd.0003308DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4230925PMC
November 2014

Neuronal injury external to the retina rapidly activates retinal glia, followed by elevation of markers for cell cycle re-entry and death in retinal ganglion cells.

PLoS One 2014 1;9(7):e101349. Epub 2014 Jul 1.

Lady Davis Institute-Jewish General Hospital, Montreal, Quebec, Canada; Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada; Department of Oncology and the Cancer Center, McGill University, Montreal, Quebec, Canada.

Retinal ganglion cells (RGCs) are neurons that relay visual signals from the retina to the brain. The RGC cell bodies reside in the retina and their fibers form the optic nerve. Full transection (axotomy) of the optic nerve is an extra-retinal injury model of RGC degeneration. Optic nerve transection permits time-kinetic studies of neurodegenerative mechanisms in neurons and resident glia of the retina, the early events of which are reported here. One day after injury, and before atrophy of RGC cell bodies was apparent, glia had increased levels of phospho-Akt, phospho-S6, and phospho-ERK1/2; however, these signals were not detected in injured RGCs. Three days after injury there were increased levels of phospho-Rb and cyclin A proteins detected in RGCs, whereas these signals were not detected in glia. DNA hyperploidy was also detected in RGCs, indicative of cell cycle re-entry by these post-mitotic neurons. These events culminated in RGC death, which is delayed by pharmacological inhibition of the MAPK/ERK pathway. Our data show that a remote injury to RGC axons rapidly conveys a signal that activates retinal glia, followed by RGC cell cycle re-entry, DNA hyperploidy, and neuronal death that is delayed by preventing glial MAPK/ERK activation. These results demonstrate that complex and variable neuro-glia interactions regulate healthy and injured states in the adult mammalian retina.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0101349PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4077807PMC
November 2015

From amoeba to macrophages: exploring the molecular mechanisms of Legionella pneumophila infection in both hosts.

Curr Top Microbiol Immunol 2013 ;376:1-34

Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR, 3525, Paris, France.

Legionella pneumophila is a Gram-negative bacterium and the causative agent of Legionnaires' disease. It replicates within amoeba and infects accidentally human macrophages. Several similarities are seen in the L. pneumophila-infection cycle in both hosts, suggesting that the tools necessary for macrophage infection may have evolved during co-evolution of L. pneumophila and amoeba. The establishment of the Legionella-containing vacuole (LCV) within the host cytoplasm requires the remodeling of the LCV surface and the hijacking of vesicles and organelles. Then L. pneumophila replicates in a safe intracellular niche in amoeba and macrophages. In this review we will summarize the existing knowledge of the L. pneumophila infection cycle in both hosts at the molecular level and compare the factors involved within amoeba and macrophages. This knowledge will be discussed in the light of recent findings from the Acanthamoeba castellanii genome analyses suggesting the existence of a primitive immune-like system in amoeba.
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http://dx.doi.org/10.1007/82_2013_351DOI Listing
July 2014

Ordering human CD34+CD10-CD19+ pre/pro-B-cell and CD19- common lymphoid progenitor stages in two pro-B-cell development pathways.

Proc Natl Acad Sci U S A 2010 Mar 15;107(13):5925-30. Epub 2010 Mar 15.

Departamento de Medicina, Universidad de Alcalá, Alcalá de Henares 28805, Spain.

Studies here respond to two long-standing questions: Are human "pre/pro-B" CD34(+)CD10(-)CD19(+) and "common lymphoid progenitor (CLP)/early-B" CD34(+)CD10(+)CD19(-) alternate precursors to "pro-B" CD34(+)CD19(+)CD10(+) cells, and do the pro-B cells that arise from these progenitors belong to the same or distinct B-cell development pathways? Using flow cytometry, gene expression profiling, and Ig V(H)-D-J(H) sequencing, we monitor the initial 10 generations of development of sorted cord blood CD34(high)Lineage(-) pluripotential progenitors growing in bone marrow S17 stroma cocultures. We show that (i) multipotent progenitors (CD34(+)CD45RA(+)CD10(-)CD19(-)) directly generate an initial wave of Pax5(+)TdT(-) "unilineage" pre/pro-B cells and a later wave of "multilineage" CLP/early-B cells and (ii) the cells generated in these successive stages act as precursors for distinct pro-B cells through two independent layered pathways. Studies by others have tracked the origin of B-lineage leukemias in elderly mice to the mouse B-1a pre/pro-B lineage, which lacks the TdT activity that diversifies the V(H)-D-J(H) Ig heavy chain joints found in the early-B or B-2 lineage. Here, we show a similar divergence in human B-cell development pathways between the Pax5(+)TdT(-) pre/pro-B differentiation pathway that gives rise to infant B-lineage leukemias and the early-B pathway.
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http://dx.doi.org/10.1073/pnas.0907942107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851857PMC
March 2010

Somatic tetraploidy in specific chick retinal ganglion cells induced by nerve growth factor.

Proc Natl Acad Sci U S A 2010 Jan 14;107(1):109-14. Epub 2009 Dec 14.

Department of Molecular, Cellular and Developmental Neurobiology, Instituto Cajal, Consejo Superior de Investigaciones Cientificas, Avenida Doctor Arce 37, E-28002 Madrid, Spain.

A subset of neurons in the normal vertebrate nervous system contains double the normal amount of DNA in their nuclei. These neurons are all thought to derive from aberrant mitoses in neuronal precursor cells. Here we show that endogenous NGF induces DNA replication in a subpopulation of differentiating chick retinal ganglion cells that express both the neurotrophin receptor p75 and the E2F1 transcription factor, but that lack the retinoblastoma protein. Many of these neurons avoid G2/M transition and remain alive in the retina as tetraploid cells with large cell somas and extensive dendritic trees, and most of them express beta2 nicotinic acetylcholine receptor subunits, a specific marker of retinal ganglion cells innervating lamina F in the stratum-griseum-et-fibrosum-superficiale of the tectal cortex. Tetraploid neurons were also observed in the adult mouse retina. Thus, a developmental program leading to somatic tetraploidy in specific retinal neurons exists in vertebrates. This program might occur in other vertebrate neurons during normal or pathological situations.
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http://dx.doi.org/10.1073/pnas.0906121107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2806721PMC
January 2010

Tumor cells deactivate human monocytes by up-regulating IL-1 receptor associated kinase-M expression via CD44 and TLR4.

J Immunol 2005 Mar;174(5):3032-40

Research Unit, Department of Surgical Research, La Paz Hospital, Madrid, Spain.

Although blood monocytes possess significant cytotoxic activity against tumor cells, tumor-infiltrating monocytes are commonly deactivated in cancer patients. Monocytes pre-exposed to tumor cells show significantly decreased expression levels of TNF-alpha, IL-12p40, and IL-1R-associated kinase (IRAK)-1. Activation of the Ser/Thr kinase IRAK-1 is an important event in several inflammatory processes. By contrast, another IRAK family member, IRAK-M, negatively regulates this pathway, and is up-regulated in cultures of endotoxin-tolerant monocytes and in monocytes from septic patients within the timeframe of tolerance. In this study, we show that IRAK-M expression is enhanced at the mRNA and protein level in human monocytes cultured in the presence of tumor cells. IRAK-M was induced in monocytes upon coculturing with different tumor cells, as well as by fixed tumor cells and medium supplemented with the supernatant from tumor cell cultures. Moreover, blood monocytes from patients with chronic myeloid leukemia and patients with metastasis also overexpressed IRAK-M. Low concentrations of hyaluronan, a cell surface glycosaminoglycan released by tumor cells, also up-regulated IRAK-M. The induction of IRAK-M by hyaluronan and tumor cells was abolished by incubation with anti-CD44 or anti-TLR4 blocking Abs. Furthermore, down-regulation of IRAK-M expression by small interfering RNAs specific for IRAK-M reinstates both TNF-alpha mRNA expression and protein production in human monocytes re-exposed to a tumor cell line. Altogether, our findings indicate that deactivation of human monocytes in the presence of tumor cells involves IRAK-M up-regulation, and this effect appears to be mediated by hyaluronan through the engagement of CD44 and TLR4.
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http://dx.doi.org/10.4049/jimmunol.174.5.3032DOI Listing
March 2005

Nitric oxide activates the expression of IRAK-M via the release of TNF-alpha in human monocytes.

Nitric Oxide 2004 Jun;10(4):213-20

Research Unit, Department of Surgical Research, La Paz Hospital, Madrid 28046, Spain.

The activation of interleukin receptor associated kinases (IRAK) is an important event in several inflammatory processes. However, exposing monocytes to a nitric oxide (NO) donor inhibits the activity of IRAK-1 and its molecular interaction with TNF receptor associated factor-6 (TRAF6). Despite the fact that NO is known to regulate many events in the immune and vascular system, the mechanism that underlies this inhibition remains unknown. We have recently demonstrated that IRAK-M inhibits the TLR/IRAK pathway during endotoxin tolerance and thus, we hypothesized that IRAK-M may be involved in the inhibition of IRAK-1 activity in the presence of NO. Hence, we have analyzed the expression of IRAK-M in human monocytes following exposure to a NO donor (GSNO) and we have observed that GSNO was capable of inducing IRAK-M mRNA and protein expression 8 and 20 h after stimulation, respectively. It is known that NO induces the expression of TNF-alpha in monocytes and we found that exposure to TNF-alpha induced IRAK-M mRNA expression in human monocytes within 2 h of stimulation. Furthermore, the expression of IRAK-M induced by GSNO was inhibited by the presence of a blocking antibody raised against TNF-alpha. Thus, our data indicate that stimulation of human monocytes with a NO donor results in a clear induction of IRAK-M and this is dependent on the release of TNF-alpha by this kind of cells.
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http://dx.doi.org/10.1016/j.niox.2004.04.007DOI Listing
June 2004

Rapid up-regulation of IRAK-M expression following a second endotoxin challenge in human monocytes and in monocytes isolated from septic patients.

Biochem Biophys Res Commun 2003 Nov;311(2):465-72

Research Unit, Department of Surgical Research, La Paz Hospital, Madrid 28046, Spain.

The exposure of human monocytes to the gram-negative endotoxin LPS provokes them to enter a transient state in which they are refractory to further stimulation by LPS. This phenomenon is known as 'endotoxin tolerance' (ET) and it is characterized by a decrease in leukocyte proinflammatory cytokine production in response to LPS. In the present study, we have analyzed the expression of IRAK-M mRNA and protein in a human model of ET using human monocytes isolated from peripheral blood. In these monocyte cultures, IRAK-M mRNA was expressed 6h after stimulation with different doses of LPS. However, endotoxin pretreatment induced a more immediate up-regulation of IRAK-M gene expression, transcripts appearing only one hour after a second LPS-challenge, and the production of high levels of IRAK-M protein in these tolerant monocytes. We also analyzed the response of monocytes isolated from septic patients within a temporal tolerance timeframe when stimulated ex vivo with LPS. In contrast to monocytes from healthy volunteers and patients outside of the tolerance timeframe, monocytes from septic patients rapidly expressed IRAK-M mRNA when stimulated with LPS ex vivo. Moreover, the expression of IRAK-M mRNA was more rapidly induced in the presence of a PI3K inhibitor, suggesting a connection between these two kinases. Thus, our data indicate that IRAK-M could play a pivotal role in the process of ET in human monocytes and provide evidence that PI3K is involved in regulating its expression.
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http://dx.doi.org/10.1016/j.bbrc.2003.10.019DOI Listing
November 2003
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