Disruption of GCN2 Pathway Aggravates Vascular and Parenchymal Remodeling during Pulmonary Fibrosis.

Pulmonary fibrosis (PF) and pulmonary hypertension (PH) are chronic diseases of the pulmonary parenchyma and circulation, respectively, which may coexist, but underlying mechanisms remain elusive. Mutations in the GCN2 (general control nonderepressible 2) gene (EIF2AK4 [eukaryotic translation initiation factor 2 alpha kinase 4]) were recently associated with pulmonary veno-occlusive disease. The aim of this study is to explore the involvement of the GCN2/eIF2α (eukaryotic initiation factor 2α) pathway in the development of PH during PF, in both human disease and in a laboratory animal model. Lung tissue from patients with PF with or without PH was collected at the time of lung transplantation, and control tissue was obtained from tumor resection surgery. Experimental lung disease was induced in either male wild-type or EIF2AK4-mutated Sprague-Dawley rats, randomly receiving a single intratracheal instillation of bleomycin or saline. Hemodynamic studies and organ collection were performed 3 weeks after instillation. Only significant results (P < 0.05) are presented. In PF lung tissue, GCN2 protein expression was decreased compared with control tissue. GCN2 expression was reduced in CD31+ endothelial cells. In line with human data, GCN2 protein expression was decreased in the lung of bleomycin rats compared with saline. EIF2AK4-mutated rats treated with bleomycin showed increased parenchymal fibrosis (hydroxyproline concentrations) and vascular remodeling (media wall thickness) as well as increased right ventricular systolic pressure compared with wild-type animals. Our data show that GCN2 is dysregulated in both humans and in an animal model of combined PF and PH. The possibility of a causative implication of GCN2 dysregulation in PF and/or PH development should be further studied.

Usefulness of FAPα assessment in bronchoalveolar lavage as a marker of fibrogenesis: results of a preclinical study and first report in patients with idiopathic pulmonary fibrosis.

BACKGROUND: Fibroblast activation protein-α (FAPα) is a marker of activated fibroblasts that can be selectively targeted by an inhibitor (FAPI) and visualised by PET/CT imaging. We evaluated whether the measurement of FAPα in bronchoalveolar lavage fluids (BALF) and the uptake of FAPI by PET/CT could be used as biomarkers of fibrogenesis. METHODS: The dynamics of lung uptake of 18F-labeled FAPI ([18F]FAPI-74) was assessed in the bleomycin mouse model at various time points and using different concentrations of bleomycin by PET/CT. FAPα was measured in BALFs from these bleomycin-treated and control mice. FAPα levels were also assessed in BALFs from controls and patients with idiopathic pulmonary fibrosis (IPF). RESULTS: Bleomycin-treated mice presented a significantly higher uptake of [18F]FAPI-74 during lung fibrinogenesis (days 10 and 16 after instillation) compared to control mice. No significant difference was observed at initial inflammatory phase (3 days) and when fibrosis was already established (28 days). [18F]FAPI-74 tracer was unable to show a dose-response to bleomycin treatment. On the other hand, BALF FAPα levels were steeply higher in bleomycin-treated mice at day 10 and a significant dose-response effect was observed. Moreover, FAPα levels were strongly correlated with lung fibrosis as measured by the modified Aschroft histological analysis, hydroxyproline and the percentage of weight loss. Importantly, higher levels of FAPα were observed in IPF patients where the disease was progressing as compared to stable patients and controls. Moreover, patients with FAPα BALF levels higher than 192.5 pg/mL presented a higher risk of progression, transplantation or death compared to patients with lower levels. CONCLUSIONS: Our preclinical data highlight a specific increase of [18F]FAPI-74 lung uptake during the fibrotic phase of the bleomycin murine model. The measurement of FAPα in BALF appears to be a promising marker of the fibrotic activity in preclinical models of lung fibrosis and in IPF patients. Further studies are required to confirm the role of FAPα in BALF as biomarker of IPF activity and assess the relationship between FAPα levels in BALF and [18F]FAPI-74 uptake on PET/CT in patients with fibrotic lung disease.

Gasdermin D membrane pores orchestrate IL-1α secretion from necrotic macrophages after NFS-rich silica exposure.

IL-1α is an intracellular danger signal (DAMP) released by macrophages contributing to the development of silica-induced lung inflammation. The exact molecular mechanism orchestrating IL-1α extracellular release from particle-exposed macrophages is still unclear. To delineate this process, murine J774 and bone-marrow derived macrophages were exposed to increasing concentrations (1-40 cm2/ml) of a set of amorphous and crystalline silica particles with different surface chemical features. In particular, these characteristics include the content of nearly free silanols (NFS), a silanol population responsible for silica cytotoxicity recently identified. We first observed de novo stocks of IL-1α in macrophages after silica internalization regardless of particle physico-chemical characteristics and cell stress. IL-1α intracellular production and accumulation were observed by exposing macrophages to biologically-inert or cytotoxic crystalline and amorphous silicas. In contrast, only NFS-rich reactive silica particles triggered IL-1α release into the extracellular milieu from necrotic macrophages. We demonstrate that IL-1α is actively secreted through the formation of gasdermin D (GSDMD) pores in the plasma membrane and not passively released after macrophage plasma membrane lysis. Our findings indicate that the GSDMD pore-dependent secretion of IL-1α stock from macrophages solely depends on cytotoxicity induced by NFS-rich silica. This new regulated process represents a key first event in the mechanism of silica toxicity, suitable to refine the existing adverse outcome pathway (AOP) for predicting the inflammatory activity of silicas.

Distinct Pro-Inflammatory Mechanisms Elicited by Short and Long Amosite Asbestos Fibers in Macrophages.

While exposure to long amphibolic asbestos fibers (L > 10 µm) results in the development of severe diseases including inflammation, fibrosis, and mesothelioma, the pathogenic activity associated with short fibers (L < 5 µm) is less clear. By exposing murine macrophages to short (SFA) or long (LFA) fibers of amosite asbestos different in size and surface chemistry, we observed that SFA internalization resulted in pyroptotic-related immunogenic cell death (ICD) characterized by the release of the pro-inflammatory damage signal (DAMP) IL-1α after inflammasome activation and gasdermin D (GSDMD)-pore formation. In contrast, macrophage responses to non-internalizable LFA were associated with tumor necrosis factor alpha (TNF-α) release, caspase-3 and -7 activation, and apoptosis. SFA effects exclusively resulted from Toll-like receptor 4 (TLR4), a pattern-recognition receptor (PRR) recognized for its ability to sense particles, while the response to LFA was elicited by a multifactorial ignition system involving the macrophage receptor with collagenous structure (SR-A6 or MARCO), reactive oxygen species (ROS) cascade, and TLR4. Our findings indicate that asbestos fiber size and surface features play major roles in modulating ICD and inflammatory pathways. They also suggest that SFA are biologically reactive in vitro and, therefore, their inflammatory and toxic effects in vivo should not be underestimated.

Mouse innate-like B-1 lymphocytes promote inhaled particle-induced in vitro granuloma formation and inflammation in conjunction with macrophages.

The current paradigm for explaining lung granulomatous diseases induced by inhaled particles is mainly based on macrophages. This mechanism is now challenging because B lymphocytes also infiltrate injured tissue, and the deficiency in B lymphocytes is associated with limited lung granulomas in silica-treated mice. Here, we investigated how B lymphocytes respond to micro- and nanoparticles by combining in vivo and in vitro mouse models. We first demonstrated that innate-like B-1 lymphocytes (not conventional B-2 lymphocytes or plasma cells) specifically accumulated during granuloma formation in mice instilled with crystalline silica (DQ12, 2.5 mg/mouse) and carbon nanotubes (CNT Mitsui, 0.2 mg/mouse). In comparison to macrophages, peritoneal B-1 lymphocytes purified from naïve mice were resistant to the pyroptotic activity of reactive particles (up to 1 mg/mL) but clustered to establish in vitro cell/particle aggregates. Mouse B-1 lymphocytes (not B-2 lymphocytes) in coculture with macrophages and CNT (0.1 µg/mL) organized three-dimensional spheroid structures in Matrigel and stimulated the release of TIMP-1. Furthermore, purified B-1 lymphocytes are sensitive to nanosilica toxicity through radical generation in culture. Nanosilica-exposed B-1 lymphocytes released proinflammatory cytokines and alarmins. In conclusion, our data indicate that in addition to macrophages, B-1 lymphocytes participate in micrometric particle-induced granuloma formation and display inflammatory functions in response to nanoparticles.

Aggregated Tau activates NLRP3-ASC inflammasome exacerbating exogenously seeded and non-exogenously seeded Tau pathology in vivo.

Brains of Alzheimer's disease patients are characterized by the presence of amyloid plaques and neurofibrillary tangles, both invariably associated with neuroinflammation. A crucial role for NLRP3-ASC inflammasome [NACHT, LRR and PYD domains-containing protein 3 (NLRP3)-Apoptosis-associated speck-like protein containing a CARD (ASC)] in amyloid-beta (Aß)-induced microgliosis and Aß pathology has been unequivocally identified. Aß aggregates activate NLRP3-ASC inflammasome (Halle et al. in Nat Immunol 9:857-865, 2008) and conversely NLRP3-ASC inflammasome activation exacerbates amyloid pathology in vivo (Heneka et al. in Nature 493:674-678, 2013), including by prion-like ASC-speck cross-seeding (Venegas et al. in Nature 552:355-361, 2017). However, the link between inflammasome activation, as crucial sensor of innate immunity, and Tau remains unexplored. Here, we analyzed whether Tau aggregates acting as prion-like Tau seeds can activate NLRP3-ASC inflammasome. We demonstrate that Tau seeds activate NLRP3-ASC-dependent inflammasome in primary microglia, following microglial uptake and lysosomal sorting of Tau seeds. Next, we analyzed the role of inflammasome activation in prion-like or templated seeding of Tau pathology and found significant inhibition of exogenously seeded Tau pathology by ASC deficiency in Tau transgenic mice. We furthermore demonstrate that chronic intracerebral administration of the NLRP3 inhibitor, MCC950, inhibits exogenously seeded Tau pathology. Finally, ASC deficiency also decreased non-exogenously seeded Tau pathology in Tau transgenic mice. Overall our findings demonstrate that Tau-seeding competent, aggregated Tau activates the ASC inflammasome through the NLRP3-ASC axis, and we demonstrate an exacerbating role of the NLRP3-ASC axis on exogenously and non-exogenously seeded Tau pathology in Tau mice in vivo. The NLRP3-ASC inflammasome, which is an important sensor of innate immunity and intensively explored for its role in health and disease, hence presents as an interesting therapeutic approach to target three crucial pathogenetic processes in AD, including prion-like seeding of Tau pathology, Aß pathology and neuroinflammation.

Absence of early metabolic response assessed by 18F-FDG PET/CT after initiation of antifibrotic drugs in IPF patients.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is characterized by a progressive and irreversible respiratory failure. Non-invasive markers of disease activity are essential for prognosis and evaluation of early response to anti-fibrotic treatments. OBJECTIVES: The aims of this study were to determine whether fluorodeoxyglucose ([18F]-FDG) lung uptake is reduced after initiation of pirfenidone or nintedanib and to assess its possible use as a prognostic factor. METHODS: [18F]-FDG PET/CT was performed in IPF patients and in a murine model of pulmonary fibrosis. PET/CTs were performed at day 8 and day 15 post-instillation of bleomycin in pirfenidone- or vehicule-treated mice. In IPF patients, PET-CT was performed before and 3 months after the initiation of pirfenidone or nintedanib. RESULTS: In bleomycin-treated mice, pirfenidone significantly reduced the [18F]-FDG uptake compared to vehicule-treated mice at day 15 (p < 0.001), whereas no difference was observed at day 8 after bleomycin administration. In IPF patients, [18F]-FDG lung uptake before and after 3 months of treatment by nintedanib (n = 11) or pirfenidone (n = 14) showed no significant difference regardless the antifibrotic treatment. Moreover, no difference was noticed between patients with progressive or non-progressive disease at one year of follow up. CONCLUSIONS: Pirfenidone significantly reduces the lung [18F]-FDG uptake during the fibrotic phase in a mouse model of IPF. However, these preclinical data were not confirmed in IPF patients 3 months after the initiation of antifibrotic therapy. [18F]-FDG seems therefore not useful in clinical practice to assess the early response of IPF patients to nintedanib or pirfenidone.

Cationic Nanoliposomes Are Efficiently Taken up by Alveolar Macrophages but Have Little Access to Dendritic Cells and Interstitial Macrophages in the Normal and CpG-Stimulated Lungs.

The purpose of this study was to assess whether cationic nanoliposomes could address tumor vaccines to dendritic cells in the lungs in vivo. Nanoliposomes were prepared using a cationic lipid, dimethylaminoethanecarbamoyl-cholesterol (DC-cholesterol) or dioleoyltrimethylammoniumpropane (DOTAP), and dipalmitoylphosphatidylcholine (DPPC), the most abundant phospholipid in lung surfactant. The liposomes presented a size below 175 nm and they effectively entrapped tumor antigens, an oligodeoxynucletotide containing CpG motifs (CpG) and the fluorescent dye calcein used as a tracer. Although the liposomes could permanently entrap a large fraction of the actives, they could not sustain their release in vitro. Liposomes made of DOTAP were safe to respiratory cells in vitro, while liposomes composed of DC-cholesterol were cytotoxic. DOTAP nanoliposomes were mainly taken up by alveolar macrophages following delivery to the lungs in mice. Few dendritic cells took up the liposomes, and interstitial macrophages did not take up liposomal calcein more than they took up soluble calcein. Stimulation of the innate immune system using liposomal CpG strongly enhanced uptake of calcein liposomes by all phagocytes in the lungs. Although a small percentage of dendritic cells took up the nanoliposomes, alveolar macrophages represented a major barrier to dendritic cell access in the lungs.

HIF-1α is a key mediator of the lung inflammatory potential of lithium-ion battery particles.

BACKGROUND: Li-ion batteries (LIB) are increasingly used worldwide. They are made of low solubility micrometric particles, implying a potential for inhalation toxicity in occupational settings and possibly for consumers. LiCoO2 (LCO), one of the most used cathode material, induces inflammatory and fibrotic lung responses in mice. LCO also stabilizes hypoxia-inducible factor (HIF) -1α, a factor implicated in inflammation, fibrosis and carcinogenicity. Here, we investigated the role of cobalt, nickel and HIF-1α as determinants of toxicity, and evaluated their predictive value for the lung toxicity of LIB particles in in vitro assays. RESULTS: By testing a set of 5 selected LIB particles (LCO, LiNiMnCoO2, LiNiCoAlO2) with different cobalt and nickel contents, we found a positive correlation between their in vivo lung inflammatory activity, and (i) Co and Ni particle content and their bioaccessibility and (ii) the stabilization of HIF-1α in the lung. Inhibition of HIF-1α with chetomin or PX-478 blunted the lung inflammatory response to LCO in mice. In IL-1ß deficient mice, HIF-1α was the upstream signal of the inflammatory lung response to LCO. In vitro, the level of HIF-1α stabilization induced by LIB particles in BEAS-2B cells correlated with the intensity of lung inflammation induced by the same particles in vivo. CONCLUSIONS: We conclude that HIF-1α, stabilized in lung cells by released Co and Ni ions, is a mechanism-based biomarker of lung inflammatory responses induced by LIB particles containing Co/Ni. Documenting the Co/Ni content of LIB particles, their bioaccessibility and their capacity to stabilize HIF-1α in vitro can be used to predict the lung inflammatory potential of LIB particles.

The puzzling issue of silica toxicity: are silanols bridging the gaps between surface states and pathogenicity?

BACKGROUND: Silica continues to represent an intriguing topic of fundamental and applied research across various scientific fields, from geology to physics, chemistry, cell biology, and particle toxicology. The pathogenic activity of silica is variable, depending on the physico-chemical features of the particles. In the last 50 years, crystallinity and capacity to generate free radicals have been recognized as relevant features for silica toxicity. The 'surface' also plays an important role in silica toxicity, but this term has often been used in a very general way, without defining which properties of the surface are actually driving toxicity. How the chemical features (e.g., silanols and siloxanes) and configuration of the silica surface can trigger toxic responses remains incompletely understood. MAIN BODY: Recent developments in surface chemistry, cell biology and toxicology provide new avenues to improve our understanding of the molecular mechanisms of the adverse responses to silica particles. New physico-chemical methods can finely characterize and quantify silanols at the surface of silica particles. Advanced computational modelling and atomic force microscopy offer unique opportunities to explore the intimate interactions between silica surface and membrane models or cells. In recent years, interdisciplinary research, using these tools, has built increasing evidence that surface silanols are critical determinants of the interaction between silica particles and biomolecules, membranes, cell systems, or animal models. It also has become clear that silanol configuration, and eventually biological responses, can be affected by impurities within the crystal structure, or coatings covering the particle surface. The discovery of new molecular targets of crystalline as well as amorphous silica particles in the immune system and in epithelial lung cells represents new possible toxicity pathways. Cellular recognition systems that detect specific features of the surface of silica particles have been identified. CONCLUSIONS: Interdisciplinary research bridging surface chemistry to toxicology is progressively solving the puzzling issue of the variable toxicity of silica. Further interdisciplinary research is ongoing to elucidate the intimate mechanisms of silica pathogenicity, to possibly mitigate or reduce surface reactivity.

CCR2+ monocytic myeloid-derived suppressor cells (M-MDSCs) inhibit collagen degradation and promote lung fibrosis by producing transforming growth factor-ß1.

Monocytes infiltrating scar tissue are predominantly viewed as progenitor cells. Here, we show that tissue CCR2+ monocytes have specific immunosuppressive and profibrotic functions. CCR2+ monocytic cells are acutely recruited to the lung before the onset of silica-induced fibrosis in mice. These tissue monocytes are defined as monocytic myeloid-derived suppressor cells (M-MDSCs) because they significantly suppress T-lymphocyte proliferation in vitro. M-MDSCs collected from silica-treated mice also express transforming growth factor (TGF)-ß1, which stimulates lung fibroblasts to release tissue inhibitor of metalloproteinase (TIMP)-1, an inhibitor of metalloproteinase collagenolytic activity. By using LysMCreCCR2loxP/loxP mice, we show that limiting CCR2+ M-MDSC accumulation reduces the pulmonary contents of TGF-ß1, TIMP-1 and collagen after silica treatment. M-MDSCs do not differentiate into lung macrophages, granulocytes or fibrocytes during pulmonary fibrogenesis. Collectively, our data indicate that M-MDSCs contribute to lung fibrosis by specifically promoting a non-degrading collagen microenvironment. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

New interplay between interstitial and alveolar macrophages explains pulmonary alveolar proteinosis (PAP) induced by indium tin oxide particles.

Occupational exposure to indium tin oxide (ITO) particles has been associated with the development of severe lung diseases, including pulmonary alveolar proteinosis (PAP). The mechanisms of this lung toxicity remain unknown. Here, we reveal the respective roles of resident alveolar (Siglec-Fhigh AM) and recruited interstitial (Siglec-Flow IM) macrophages contributing in concert to the development of PAP. In mice treated with ITO particles, PAP is specifically associated with IL-1α (not GM-CSF) deficiency and Siglec-Fhigh AM (not Siglec-Flow IM) depletion. Mechanistically, ITO particles are preferentially phagocytosed and dissolved to soluble In3+ by Siglec-Flow IM. In contrast, Siglec-Fhigh AM weakly phagocytose or dissolve ITO particles, but are sensitive to released In3+ through the expression of the transferrin receptor-1 (TfR1). Blocking pulmonary Siglec-Flow IM recruitment in CCR2-deficient mice reduces ITO particle dissolution, In3+ release, Siglec-Fhigh AM depletion, and PAP formation. Restoration of IL-1-related Siglec-Fhigh AM also prevented ITO-induced PAP. We identified a new mechanism of secondary PAP development according to which metal ions released from inhaled particles by phagocytic IM disturb IL-1α-dependent AM self-maintenance and, in turn, alveolar clearance.

The NLRP3 Inflammasome Has a Critical Role in Peritoneal Dialysis-Related Peritonitis.

Bacterial peritonitis remains the main cause of technique failure in peritoneal dialysis (PD). During peritonitis, the peritoneal membrane undergoes structural and functional alterations that are mediated by IL-1ß The NLRP3 inflammasome is a caspase-1-activating multiprotein complex that links sensing of microbial and stress products to activation of proinflammatory cytokines, including IL-1ß The potential roles of the NLRP3 inflammasome and IL-1ß in the peritoneal membrane during acute peritonitis have not been investigated. Here, we show that the NLRP3 inflammasome is activated during acute bacterial peritonitis in patients on PD, and this activation associates with the release of IL-1ß in the dialysate. In mice, lipopolysaccharide- or Escherichia coli-induced peritonitis led to IL-1ß release in the peritoneal membrane. The genetic deletion of Nalp3, which encodes NLRP3, abrogated defects in solute transport during acute peritonitis and restored ultrafiltration. In human umbilical vein endothelial cells, IL-1ß treatment directly enhanced endothelial cell proliferation and increased microvascular permeability. These in vitro effects require endothelial IL-1 receptors, shown by immunofluorescence to be expressed in peritoneal capillaries in mice. Furthermore, administration of the IL-1ß receptor antagonist, anakinra, efficiently decreased nitric oxide production and vascular proliferation and restored peritoneal function in mouse models of peritonitis, even in mice treated with standard-of-care antibiotherapy. These data demonstrate that NLRP3 activation and IL-1ß release have a critical role in solute transport defects and tissue remodeling during PD-related peritonitis. Blockade of the NLRP3/IL-1ß axis offers a novel method for rescuing morphologic alterations and transport defects during acute peritonitis.

Vardenafil reduces macrophage pro-inflammatory overresponses in cystic fibrosis through PDE5- and CFTR-dependent mechanisms.

Chronic inflammation that progressively disrupts the lung tissue is a hallmark of cystic fibrosis (CF). In mice, vardenafil, an inhibitor of phosphodiesterase type 5 (PDE5), restores transepithelial ion transport and corrects mislocalization of the most common CF mutation, F508del-CFTR. It also reduces lung pro-inflammatory responses in mice and in patients with CF. To test the hypothesis that macrophages are target effector cells of the immunomo-dulatory effect of vardenafil, we isolated lung macrophages from mice homozygous for the F508del mutation or invalidated for the cftr gene and from their corresponding wild-type (WT) littermates. We then evaluated the effect of vardenafil on the classical M1 polarization, mirroring release of pro-inflammatory cytokines. We confirmed that macrophages from different body compartments express CF transmembrane conductance regulator (CFTR) and showed that vardenafil targets the cells through PDE5- and CFTR-dependent mechanisms. In the presence of the F508del mutation, vardenafil down-regulated overresponses of the M1 markers, tumour necrosis factor (TNF)-α and inducible nitric oxide synthase (NOS)-2. Our study identifies lung macrophages as target cells of the anti-inflammatory effect of vardenafil in CF and supports the view that the drug is potentially beneficial for treating CF as it combines rescue of CFTR protein and anti-inflammatory properties.

Can serum cytokine profile discriminate irritant-induced and allergen-induced symptoms? A cross-sectional study in workers mostly exposed to laboratory animals.

BACKGROUND: In workers exposed mostly to laboratory animals (LA), symptoms may be due to irritants or allergens. Correct aetiological diagnosis is important for health surveillance. OBJECTIVES: This study aims to test whether work-related (WR) allergen-induced symptoms are associated with a cytokine profile distinct from that due to irritants. METHODS: In a cross-sectional study (n=114), WR respiratory and/or skin symptoms were assessed through a standardised clinical examination and sensitisation to rat and/or mouse allergen determined by serum immunoglobulin E. Serum cytokine concentrations were measured by multiplex assays. The predefined cytokine profiles 'sensitiser' (interleukin (IL)-4, IL-5, IL-13, eotaxin-1) and 'irritation' (IL-8, IL-17A, IL-17F, IL-22) were considered positive, when ≥3 concentrations exceeded the 95th percentile of the asymptomatic non-sensitised group. Results were examined by hierarchical clustering analyses (HCA) and multiple linear regression. Explorative analyses were carried out for nine additional cytokines. Exposure to allergens and endotoxin was assessed in a subpopulation. RESULTS: The prevalence of the profile 'irritation' was comparable in 28 symptomatic non-sensitised workers and 71 asymptomatic non-sensitised workers. HCA showed that nearly all symptomatic non-sensitised workers were gathered in two subclusters, characterised by high IL-17A levels, but different IL-8 levels. Multiple linear regression identified drug consumption and current complaints as confounders. Sensitised subjects were too few (n=14) for testing the profile 'sensitiser'. CONCLUSIONS: In this unselected population of LA workers, the profile 'irritation' did not prove to be a valuable health surveillance tool. Low power precluded assessment of the profile 'sensitiser'. The increased IL-17A concentration may originate from irritative constituents of organic dust.

Activation of phagocytic activity in astrocytes by reduced expression of the inflammasome component ASC and its implication in a mouse model of Alzheimer disease.

BACKGROUND: The proinflammatory cytokine interleukin-1ß (IL-1ß) is overexpressed in Alzheimer disease (AD) as a key regulator of neuroinflammation. Amyloid-ß (Aß) peptide triggers activation of inflammasomes, protein complexes responsible for IL-1ß maturation in microglial cells. Downregulation of NALP3 (NACHT, LRR, and PYD domains-containing protein 3) inflammasome has been shown to decrease amyloid load and rescue cognitive deficits in a mouse model of AD. Whereas activation of inflammasome in microglial cells has been described in AD, no data are currently available concerning activation of inflammasome in astrocytes, although they are involved in inflammatory response and phagocytosis. Here, by targeting the inflammasome adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD domain), we investigated the influence of activation of the inflammasome on the phagocytic activity of astrocytes. METHODS: We used an ASC knockout mouse model, as ASC is a central protein in the inflammasome, acting as an adaptor and stabilizer of the complex and thus critical for its activation. Lipopolysaccharide (LPS)-primed primary cultures of astrocytes from newborn mice were utilized to evaluate Aß-induced inflammasome activation by measuring IL-1ß release by ECLIA (electro-chemiluminescence immunoassay). Phagocytosis efficiency was measured by incorporation of bioparticles, and the release of the chemokine CCL3 (C-C motif ligand 3) was measured by ECLIA. ASC mice were crossbred with 5xFAD (familial Alzheimer disease) mice and tested for spatial reference memory using the Morris water maze (MWM) at 7-8 months of age. Amyloid load and CCL3 were quantified by thioflavine S staining and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. RESULTS: Cultured astrocytes primed with LPS and treated with Aß showed an ASC-dependent production of IL-1ß resulting from inflammasome activation mediated by Aß phagocytosis and cathepsin B enzymatic activity. ASC+/- astrocytes displayed a higher phagocytic activity as compared to ASC+/+ and ASC -/- cells, resulting from a higher release of the chemokine CCL3. A significant decrease in amyloid load was measured in the brain of 7-8-month-old 5xFAD mice carrying the ASC +/- genotype, correlated with an increase in CCL3 gene expression. In addition, the ASC +/- genotype rescued spatial reference memory deficits observed in 5xFAD mice. CONCLUSIONS: Our results demonstrate that Aß is able to activate astrocytic inflammasome. Downregulation of inflammasome activity increases phagocytosis in astrocytes due to the release of CCL3. This could explain why downregulation of inflammasome activity decreases amyloid load and rescues memory deficits in a mouse model of AD.

Glufosinate aerogenic exposure induces glutamate and IL-1 receptor dependent lung inflammation.

Glufosinate-ammonium (GLA), the active component of an herbicide, is known to cause neurotoxicity. GLA shares structural analogy with glutamate. It is a powerful inhibitor of glutamine synthetase (GS) and may bind to glutamate receptors. Since these potentials targets of GLA are present in lung and immune cells, we asked whether airway exposure to GLA may cause lung inflammation in mice. A single GLA exposure (1 mg/kg) induced seizures and inflammatory cell recruitment in the broncho-alveolar space, and increased myeloperoxidase (MPO), inducible NO synthase (iNOS), interstitial inflammation and disruption of alveolar septae within 6-24 h. Interleukin 1ß (IL-1ß) was increased and lung inflammation depended on IL-1 receptor 1 (IL-1R1). We demonstrate that glutamate receptor pathway is central, since the N-methyl-D-aspartate (NMDA) receptor inhibitor MK-801 prevented GLA-induced lung inflammation. Chronic exposure (0.2 mg/kg 3× per week for 4 weeks) caused moderate lung inflammation and enhanced airway hyperreactivity with significant increased airway resistance. In conclusion, GLA aerosol exposure causes glutamate signalling and IL-1R-dependent pulmonary inflammation with airway hyperreactivity in mice.

IL-1α induces CD11b(low) alveolar macrophage proliferation and maturation during granuloma formation.

Macrophages play a central role in immune and tissue responses of granulomatous lung diseases induced by pathogens and foreign bodies. Circulating monocytes are generally viewed as central precursors of these tissue effector macrophages. Here, we provide evidence that granulomas derive from alveolar macrophages serving as a local reservoir for the expansion of activated phagocytic macrophages. By exploring lung granulomatous responses to silica particles in IL-1-deficient mice, we found that the absence of IL-1α, but not IL-1ß, was associated with reduced CD11b(high) phagocytic macrophage accumulation and fewer granulomas. This defect was associated with impaired alveolar clearance and resulted in the development of pulmonary alveolar proteinosis (PAP). Reconstitution of IL-1α(-/-) mice with recombinant IL-1α restored lung clearance functions and the pulmonary accumulation of CD11b(high) phagocytic macrophages. Mechanistically, IL-1α induced the proliferation of CD11b(low) alveolar macrophages and differentiated these cells into CD11b(high) macrophages which perform critical phagocytic functions and organize granuloma. We newly discovered here that IL-1α triggers lung responses requiring macrophage proliferation and maturation from tissue-resident macrophages.

The complex cascade of cellular events governing inflammasome activation and IL-1ß processing in response to inhaled particles.

The innate immune system is the first line of defense against inhaled particles. Macrophages serve important roles in particle clearance and inflammatory reactions. Following recognition and internalization by phagocytes, particles are taken up in vesicular phagolysosomes. Intracellular phagosomal leakage, redox unbalance and ionic movements induced by toxic particles result in pro-IL-1ß expression, inflammasome complex engagement, caspase-1 activation, pro-IL-1ß cleavage, biologically-active IL-1ß release and finally inflammatory cell death termed pyroptosis. In this review, we summarize the emerging signals and pathways involved in the expression, maturation and secretion of IL-1ß during these responses to particles. We also highlight physicochemical characteristics of particles (size, surface and shape) which determine their capacity to induce inflammasome activation and IL-1ß processing.

Mesothelioma response to carbon nanotubes is associated with an early and selective accumulation of immunosuppressive monocytic cells.

BACKGROUND: The asbestos-like toxicity of some engineered carbon nanotubes (CNT), notably their capacity to induce mesothelioma, is a serious cause of concern for public health. Here we show that carcinogenic CNT induce an early and sustained immunosuppressive response characterized by the accumulation of monocytic Myeloid Derived Suppressor Cells (M-MDSC) that counteract effective immune surveillance of tumor cells. METHODS: Wistar rats and C57BL/6 mice were intraperitoneally injected with carcinogenic multi-walled Mitsui-7 CNT (CNT-7) or crocidolite asbestos. Peritoneal mesothelioma development and immune cell accumulation were assessed until 12 months. Leukocyte sub-populations were identified by recording expression of CD11b/c and His48 by flow cytometry. The immunosuppressive activity on T lymphocytes of purified peritoneal leukocytes was assessed in a co-culture assay with activated spleen cells. RESULTS: We demonstrate that long and short mesotheliomagenic CNT-7 injected in the peritoneal cavity of rats induced, like asbestos, an early and selective accumulation of monocytic cells (CD11b/c(int) and His48(hi)) which possess the ability to suppress polyclonal activation of T lymphocytes and correspond to M-MDSC. Peritoneal M-MDSC persisted during the development of peritoneal mesothelioma in CNT-7-treated rats but were only transiently recruited after non-carcinogenic CNT (CNT-M, CNT-T) injection. Peritoneal M-MDSC did not accumulate in mice which are resistant to mesothelioma development. CONCLUSIONS: Our data provide new insights into the initial pathogenic events induced by CNT, adding a new component to the adverse outcome pathway leading to mesothelioma development. The specificity of the M-MDSC response after carcinogenic CNT exposure highlights the interest of this response for detecting the ability of new nanomaterials to cause cancer.