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Cited by 41Inflammasome and immune disordersImmune Response and InflammationOccupational and environmental lung diseases

Volcanic Ash Activates the NLRP3 Inflammasome in Murine and Human Macrophages

Open access
Damby, David E., Horwell, Claire J., Baxter, Peter J., Kueppers, Ulrich, Schnurr, Max, Dingwell, Donald B., Duewell, Peter·2018·Frontiers in Immunology
DOI 10.3389/fimmu.2017.02000PMC PMC5786523
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Abstract

Volcanic ash is a heterogeneous mineral dust that is typically composed of a mixture of amorphous (glass) and crystalline (mineral) fragments. It commonly contains an abundance of the crystalline silica (SiO2) polymorph cristobalite. Inhalation of crystalline silica can induce inflammation by stimulating the NLRP3 inflammasome, a cytosolic receptor complex that plays a critical role in driving inflammatory immune responses. Ingested material results in the assembly of NLRP3, ASC and caspase-1 with subsequent secretion of the interleukin 1 family cytokine IL-1. Previous toxicology work suggests that cristobalite-bearing volcanic ash is minimally reactive, calling into question the reactivity of volcanically derived crystalline silica, in general. In this study, we target the NLRP3 inflammasome as a crystalline-silica responsive element to clarify volcanic cristobalite reactivity. We expose immortalized bone marrow-derived macrophages of genetically engineered mice and primary human peripheral blood mononuclear cells (PBMC) to ash from the Soufrière Hills volcano as well as representative, pure-phase samples of its primary componentry (volcanic glass, feldspar, cristobalite) and measure NLRP3 inflammasome activation. We demonstrate that respirable Soufrière Hills volcanic ash induces the activation of caspase-1 with subsequent release of mature IL-1β in a NLRP3 inflammasome-dependent manner. Macrophages deficient in NLRP3 inflammasome components are incapable of secreting IL-1β in response to volcanic ash ingestion. Cellular uptake induces lysosomal destabilization involving cysteine proteases. Furthermore, the response involves activation of mitochondrial stress pathways leading to the generation of reactive oxygen species (ROS). Considering ash componentry, cristobalite is the most reactive pure-phase with other components inducing only low-level IL-1β secretion. Inflammasome activation mediated by inhaled ash and its potential relevance in chronic pulmonary disease was further evidenced in PBMC using the NLRP3 small-molecule inhibitor CP-456,773 (CRID3, MCC950). Our data indicate the functional activation of the NLRP3 inflammasome by volcanic ash in murine and human macrophages in vitro. Cristobalite is identified as the apparent driver, thereby contesting previous assertions that chemical and structural imperfections may be sufficient to abrogate the reactivity of volcanically derived cristobalite. This is a novel mechanism for the stimulation of a pro-inflammatory response by volcanic particulate and provides new insight regarding chronic exposure to environmentally occurring particles.

AI snapshot

Written from the paper’s full text.

TL;DR

Respirable Soufrière Hills volcanic ash activates the NLRP3 inflammasome in LPS-primed murine macrophages and human PBMCs, inducing caspase-1 activation and mature IL-1β release. Cristobalite is the apparent driver among ash components, and the response involves lysosomal uptake, cathepsin B, and reactive oxygen species.

Key findings

  • Ash sample MRA5/6/99 induced dose-dependent IL-1β secretion only in LPS-primed wild-type macrophages; NLRP3−/−, ASC−/−, and Caspase-1/11−/− cells failed to secrete IL-1β. Human PBMCs also secreted IL-1α and IL-1β after LPS priming, and the NLRP3 inhibitor CP-456,773 potently inhibited IL-1β and, to a lesser extent, IL-1α.
  • Cristobalite triggered the strongest dose-dependent IL-1β release among pure-phase componentry; feldspar, volcanic glass, and pumice induced only low-level IL-1β and active caspase-1 p20. The ash contains ~15 wt.% crystalline silica as cristobalite, with particles <5 µm and a mode of 2 µm; surface area is 3.6 m²/g.
  • Endocytosis inhibitor latrunculin A, cathepsin B inhibitor CA-074-Me, and ROS scavenger APDC each completely inhibited ash-induced IL-1β secretion. Confocal imaging showed ash and DQ-OVA translocated to the cytosol, and ash did not induce TNFα or IL-6 without LPS priming.

Methods

  • In vitro exposures used immortalized wild-type and NLRP3−/−, ASC−/−, Caspase-1/11−/− murine bone marrow-derived macrophages and primary human PBMCs. Cells were primed with LPS (200 ng/ml for iMΦ; 100 pg/ml for PBMC) for 2 h, then stimulated with ash/componentry or controls (ATP, dAdT, nigericin, Leu-Leu-OMe); IL-1α, IL-1β, IL-6, and TNFα were measured by ELISA and western blot.
  • Particles included Soufrière Hills ash MRA5/6/99 respirable fraction, pure-phase cristobalite, labradorite feldspar, synthetic andesite glass, and cristobalite-free pumice. Samples were characterized by particle sizing, BET surface area, SEM, and XRD.
  • Inhibitor studies used latrunculin A, CA-074-ME, APDC, and CP-456,773 at 20 µM applied 1 h before stimulation. Imaging used light and confocal microscopy; statistics used Student’s t-test with significance at p ≤ 0.05, and representative data came from two independent experiments performed as triplicates.

Limitations

  • Stated: the exact mechanism by which crystalline structures act on inflammasome activation remains elusive; a link to the initial priming step is still missing; volcanic ash exposure rarely occurs in isolation, and other phases may initiate signaling.
  • Stated: clinical manifestations of exposure are presently unknown, and few epidemiological studies exist; the paper cites a clinical study that found no hilar node enlargement in chest X-rays of 37 children exposed to Soufrière Hills ash for 10 years.
  • Evident: all experiments are in vitro (murine iMΦ and human PBMC), so there is no in vivo confirmation of chronic pulmonary disease; human PBMC donors are described only as randomly selected, with no demographic or health details.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3389/fimmu.2017.02000

Cites

62 of 62 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 64 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Respirable Soufrière Hills volcanic ash induces activation of caspase-1 with subsequent release of mature IL-1β in a NLRP3 inflammasome-dependent manner in murine and human macrophages in vitro.

    “We demonstrate that respirable Soufrière Hills volcanic ash induces the activation of caspase-1 with subsequent release of mature IL-1β in a NLRP3 inflammasome-dependent manner.”
    • Also stated in: § Abstract · hedged
      “Our data indicate the functional activation of the NLRP3 inflammasome by volcanic ash in murine and human macrophages in vitro.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The in vitro responses of murine macrophages and human PBMCs to volcanic ash are relevant to human respiratory health hazard from inhaled ash.
  • Findingown data

    Volcanic ash induces activation of mature IL-1β (p17) in a moderate way compared to nigericin.

    “As expected, volcanic ash was able to induce activation of mature IL-1β, however, in a moderate way compared to the positive control nigericin, a highly potent pore-forming toxin (Figure 3B).”
    Quote in the paperSubstantial claim
  • Findingown data

    CP-456,773 potently inhibits IL-1β release and to a lesser extent IL-1α from ash-treated human PBMC.

    “The data show that CP-456,773 potently inhibited the release of IL-1β and, to a lesser extent, IL-1α (Figures 3E,F).”
    Quote in the paperSubstantial claim
  • Findingown data

    Inflammasome activation mediated by volcanic ash and its potential relevance in chronic pulmonary disease was evidenced in human PBMC using the NLRP3 small-molecule inhibitor CP-456,773 (CRID3, MCC950).

    “Inflammasome activation mediated by inhaled ash and its potential relevance in chronic pulmonary disease was further evidenced in PBMC using the NLRP3 small-molecule inhibitor CP-456,773 (CRID3, MCC950).”
    • Also stated in: § Volcanic Ash-Induced IL-1β Secretion Involves the NLRP3 Inflammasome and Caspase-1 Activation · plain
      “The data show that CP-456,773 potently inhibited the release of IL-1β and, to a lesser extent, IL-1α (Figures 3E,F).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The in vitro responses of murine macrophages and human PBMCs to volcanic ash are relevant to human respiratory health hazard from inhaled ash.
  • Findingown data

    Macrophages deficient in NLRP3 inflammasome components (NLRP3, ASC, or caspase-1/11) are incapable of secreting IL-1β in response to volcanic ash ingestion.

    “Macrophages deficient in NLRP3 inflammasome components are incapable of secreting IL-1β in response to volcanic ash ingestion.”
    • Also stated in: § Volcanic Ash-Induced IL-1β Secretion Involves the NLRP3 Inflammasome and Caspase-1 Activation · plain
      “cells with defects in NLRP3 signaling (NLRP3−/−, ASC−/−, and Caspase-1/11−/−) components failed to secrete IL-1β in response to volcanic ash exposure”
    Quote in the paperSubstantial claim
  • May combine two claims. 22
  • Classified as probably not a substantial claim. 29

  • May combine two claims.

    Findingown data

    Cristobalite is the most reactive pure-phase component of volcanic ash, with other components inducing only low-level IL-1β secretion.

    “Considering ash componentry, cristobalite is the most reactive pure-phase with other components inducing only low-level IL-1β secretion.”
    • Also stated in: § Cristobalite Is the Apparent Driver of IL-1β Secretion by Volcanic Ash · hedged
      “Of the componentry samples, the silica compound cristobalite triggered the strongest dose-dependent release of IL-1β (Figure 4A), suggesting it is the predominant driver behind production of IL-1β by volcanic ash.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The synthetic pure-phase componentry samples (cristobalite, feldspar, volcanic glass) are representative of the corresponding phases in the volcanic ash sample.

  • May combine two claims.

    Findingown data

    The ash sample MRA5/6/99 is particularly fine-grained, with particles <5 μm and a mode of 2 μm.

    “The ash sample is particularly fine-grained: scanning electron microscopy and particle sizing data of the isolated sample show that the particles are <5 µm, with a mode of 2 µm (Figure 1B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Volcanic ash was internalized by macrophages after 4 h incubation, with massive clustering of particles within the cells.

    “The material was taken up by the cells, resulting in massive clustering of particles within the cell, and the intensity of optical refraction (darker cells) illustrates the capacity of the macrophages in particle clearance.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Backscatter SEM imaging reveals a heterogeneous distribution of volcanic glass, feldspar, and cristobalite as the predominant phases in the ash sample.

    “Backscatter SEM imaging reveals a heterogeneous distribution of volcanic glass, feldspar, and cristobalite as the predominant phases (Figure 1C).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    DQ-OVA showed a distinct vesicular distribution in the absence of ash.

    “As expected, DQ-OVA showed a distinct vesicular distribution in the absence of ash.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Lat A completely inhibited ash-induced IL-1β release, whereas it had no influence on cytokine secretion mediated by nigericin.

    “Lat A completely inhibited ash-induced IL-1β release, whereas it had no influence on cytokine secretion mediated by the pore-forming toxin nigericin, strengthening the role of lysosomal uptake in response to volcanic ash.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Ash and DQ-OVA translocated to the cytosol and showed partial co-localization.

    “Furthermore, ash and DQ-OVA translocated to the cytosol and showed partial co-localization.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Ash-induced IL-1β secretion is caspase-1 and ASC dependent, identifying involvement of an inflammasome-mediated pathway.

    “This secretion is caspase-1 and ASC dependent, identifying the involvement of an inflammasome-mediated pathway.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Ash-treated cells showed enlarged vesicles with enhanced particle uptake.

    “In contrast, ash-treated cells showed enlarged vesicles with enhanced particle uptake (Figure 5B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Silencing of murine NLRP3 and inhibition of human NLRP3 completely abolished ash-induced IL-1β secretion.

    “Critically, silencing of the murine NLRP3 gene as well as inhibition of human NLRP3 completely abolished ash-induced IL-1β secretion.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Inhibition of cathepsin B completely inhibited IL-1β secretion, compared to partial effects observed with the lysosomotropic agent Leu-Leu-OMe.

    “Inhibition of cathepsin B completely inhibited IL-1β secretion, compared to partial effects observed with the lysosomotropic agent l-leucyl-l-leucine methyl ester (Leu-Leu-OMe).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    IL-1α is biologically active, in contrast to IL-1β, and represents a key alarmin from dying cells, playing a pivotal role in acute particle-induced lung inflammation.

    “The closely related homolog IL-1α is, in contrast to IL-1β, biologically active, although little is known about its activation and secretion. IL-1α represents a key alarmin from dying cells and plays a pivotal role in acute particle-induced lung inflammation (37).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [37] Rabolli, 2014, The alarmin IL-1α is a master cytokine in acute lung inflammation induced by silica micro- and nanoparticles, Part Fibre Toxicol source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    IL-1 cytokines are potent mediators of innate immunity in response to crystalline silica exposure and have been implicated in the pathophysiology of human and experimental diseases.

    “IL-1 cytokines are potent mediators of innate immunity in response to crystalline silica exposure (23, 24) and have been implicated in the pathophysiology of human and experimental diseases (25, 26).”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [23] Driscoll, 1991, Cytokine and growth factor release by alveolar macrophages: potential biomarkers of pulmonary toxicity, Toxicol Pathol source

      Not checked in the free run.

    • cites [24] Davis, 1998, Persistent overexpression of interleukin-1beta and tumor necrosis factor-alpha in murine silicosis, J Environ Pathol Toxicol Oncol

      Not checked in the free run.

    • cites [25] Rimal, 2005, Basic pathogenetic mechanisms in silicosis: current understanding, Curr Opin Pulm Med source

      Not checked in the free run.

    • cites [26] Huaux, 2007, New developments in the understanding of immunology in silicosis, Curr Opin Allergy Clin Immunol source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Volcanic ash is successfully phagocytosed by macrophages with little associated decrease in cell viability.

    “This aligns with other recent observations of successful phagocytosis of volcanic ash by macrophages with little associated decrease in cell viability (10, 46).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [10] Damby, 2016, The in vitro respiratory toxicity of cristobalite-bearing volcanic ash, Environ Res source

      Not checked in the free run.

    • cites [46] Monick, 2013, Effects of Eyjafjallajökull volcanic ash on innate immune system responses and bacterial growth in vitro, Environ Health Perspect source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Particle size is important for entering the endosomal compartment, as reported for silica crystals with an average size of 1-2 μm.

    “However, particle size is known to be important for entering the endosomal compartment, as reported for silica crystals with an average size of 1–2 µm (22).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [22] Hornung, 2008, Silica crystals and aluminum salts activate the NALP3 inflammasome through phagosomal destabilization, Nat Immunol source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Inflammation plays a pivotal role in crystal-driven disease progression and can be observed in patients with particle-induced lung diseases.

    “Inflammation plays a pivotal role in crystal-driven disease progression and can be observed in patients with particle-induced lung diseases (17).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [17] Kamp, 1999, The molecular basis of asbestos induced lung injury, Thorax source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The inhalation and deposition of particulate pollutants such as diesel exhaust, asbestos, or silica in the small airways is known to induce inflammatory responses leading to sustained inflammation, lung fibrosis, and cancer.

    “The inhalation and deposition of particulate pollutants, such as diesel exhaust, asbestos, or silica, in the small airways is known to induce inflammatory responses leading to sustained inflammation, lung fibrosis, and cancer (22, 25).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [22] Hornung, 2008, Silica crystals and aluminum salts activate the NALP3 inflammasome through phagosomal destabilization, Nat Immunol source

      Not checked in the free run.

    • cites [25] Rimal, 2005, Basic pathogenetic mechanisms in silicosis: current understanding, Curr Opin Pulm Med source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Previous toxicology work suggests that cristobalite-bearing volcanic ash is minimally reactive.

    “Previous toxicology work suggests that cristobalite-bearing volcanic ash is minimally reactive, calling into question the reactivity of volcanically derived crystalline silica, in general.”
    • Also stated in: § Introduction · hedged
      “Experimentally, cristobalite-bearing volcanic ash has incited granuloma formation in vivo (1, 11), but it is consistently less inflammatory and fibrogenic than would be expected for a crystalline silica-bearing dust (3, 12).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [3] Horwell, 2006, The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation, Bull Volcanol source

      Not checked in the free run.

    • cites [12] Wilson, 2000, In vitro toxicology of respirable Montserrat volcanic ash, Occup Environ Med source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The ash sample MRA5/6/99 comprises ~15 wt.% crystalline silica as cristobalite, with other major constituents being volcanic glass and plagioclase feldspar.

    “The sample comprises ~15 wt.% crystalline silica as cristobalite, with the other major constituents being volcanic glass (amorphous silica) and plagioclase feldspar; additional minor phases identified were hornblende, orthopyroxene, titanomagnetite, and oxides (10, 29).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [10] Damby, 2016, The in vitro respiratory toxicity of cristobalite-bearing volcanic ash, Environ Res source

      Not checked in the free run.

    • cites [29] Horwell, 2003, The characterisation of respirable volcanic ash from the Soufriere Hills Volcano, Montserrat, with implications for health hazard, Bull Volcanol source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Caspase-1 belongs to the inflammatory caspases and leads to the processing and secretion of IL-1β and IL-18 into their active forms.

    “Caspase-1 belongs to the inflammatory caspases and leads to the processing and secretion of the pro-inflammatory cytokines interleukin-1 beta (IL-1β) and IL-18 into their active forms (21).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [21] Martinon, 2002, The inflammasome: a molecular platform triggering activation of inflammatory caspases and processing of proIL-beta, Mol Cell source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    The capacity of volcanic cristobalite to incite disease remains enigmatic.

    “These discoveries have defined the environmental side of the hazard; however, the capacity of volcanic cristobalite to incite disease remains enigmatic (7, 8).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [7] Damby, 2012

      Not checked in the free run.

    • cites [8] Horwell, 2012, The structure of volcanic cristobalite in relation to its toxicity; relevance for the variable crystalline silica hazard, Part Fibre Toxicol source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Inhalation of crystalline silica can induce inflammation by stimulating the NLRP3 inflammasome.

    “Inhalation of crystalline silica can induce inflammation by stimulating the NLRP3 inflammasome, a cytosolic receptor complex that plays a critical role in driving inflammatory immune responses.”
    • Also stated in: § Introduction · plain
      “it has been shown that danger-associated molecular patterns, such as endogenous uric acid (gout) or cholesterol (atherosclerosis) as well as exogenous particles like asbestos (asbestosis) or crystalline silica (silicosis), share features of crystalline particles that activate the NLRP3 inflammasome (also known as CIAS1, NALP3, or cryopyrin) (18–20).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [18] Martinon, 2006, Gout-associated uric acid crystals activate the NALP3 inflammasome, Nature source

      Not checked in the free run.

    • cites [19] Dostert, 2008, Innate immune activation through Nalp3 inflammasome sensing of asbestos and silica, Science source

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    • cites [20] Duewell, 2010, NLRP3 inflammasomes are required for atherogenesis and activated by cholesterol crystals, Nature source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Instigation of chronic disease by crystalline silica is NLRP3-dependent.

    “the observation that instigation of chronic disease by crystalline silica is NLRP3-dependent (27, 28)”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [27] Mossman, 2013, Bioreactivity of the crystalline silica polymorphs, quartz and cristobalite, and implications for occupational exposure limits (OELs), Crit Rev Toxicol source

      Not checked in the free run.

    • cites [28] Cassel, 2008, The Nalp3 inflammasome is essential for the development of silicosis, Proc Natl Acad Sci U S A source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Diverse crystalline material activates the NLRP3 inflammasome via phagosomal destabilization with lysosomal content leaking into the cytosol.

    “Diverse crystalline material has been reported to activate the NLRP3 inflammasome via phagosomal destabilization with lysosomal content leaking into the cytosol.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [22] Hornung, 2008, Silica crystals and aluminum salts activate the NALP3 inflammasome through phagosomal destabilization, Nat Immunol source

      Not checked in the free run.

    • cites [34] Zhou, 2010, Thioredoxin-interacting protein links oxidative stress to inflammasome activation, Nat Immunol source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Ongoing work has constrained the presence of cristobalite in ash to eruptions that involve lava domes or incorporate pre-existing, altered flow-units.

    “Ongoing work has constrained the presence of cristobalite in ash to eruptions that involve lava domes or incorporate pre-existing, altered flow-units (5, 6).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [5] Baxter, 1999, Cristobalite in volcanic ash of the Soufriere Hills Volcano, Montserrat, British West Indies, Science source

      Not checked in the free run.

    • cites [6] Horwell, 2013, The nature and formation of cristobalite at the Soufrière Hills volcano, Montserrat: implications for the petrology and stability of silicic lava domes, Bull Volcanol source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Structural and chemical defects of volcanic cristobalite, together with its presence in a heterogeneous dust, have been implicated in its reduced potency.

    “indeed, structural and chemical defects of volcanic cristobalite (which contains up to 3 wt.% aluminum) together with its presence in a heterogeneous dust have all been previously implicated in its reduced potency (8, 14, 15).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [8] Horwell, 2012, The structure of volcanic cristobalite in relation to its toxicity; relevance for the variable crystalline silica hazard, Part Fibre Toxicol source

      Not checked in the free run.

    • cites [14] Damby, 2014, The alpha-beta phase transition in volcanic cristobalite, J Appl Crystallogr source

      Not checked in the free run.

    • cites [15] Nattrass, 2017, The effect of aluminium and sodium impurities on the in vitro toxicity and pro-inflammatory potential of cristobalite, Environ Res source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Crystalline silica in other mixed-mineral dusts is variably reactive, and its pathogenicity may be altered by inherent structural and chemical defects and by other constituents in the dust.

    “Crystalline silica in other mixed-mineral dusts is known to be variably reactive (13), whereby its pathogenicity may be altered by inherent structural and chemical defects along with effects imparted by other constituents in a mixed-phase dust”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Donaldson, 1998, The quartz hazard: a variable entity, Ann Occup Hyg source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The ash sample MRA5/6/99 has been previously reported to be successfully internalized by differentiated THP-1 cells.

    “The ash sample has been previously reported to be successfully internalized by differentiated THP-1 cells, the human monocytic cell line (10).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [10] Damby, 2016, The in vitro respiratory toxicity of cristobalite-bearing volcanic ash, Environ Res source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    The NLRP3 inflammasome senses crystalline danger signals that can occur during autoinflammatory diseases and environmental diseases.

    “The NLRP3 inflammasome senses crystalline danger signals that can occur during autoinflammatory diseases, such as gout or atherosclerosis, and environmental diseases, such as silicosis or asbestosis (18, 20, 22).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [18] Martinon, 2006, Gout-associated uric acid crystals activate the NALP3 inflammasome, Nature source

      Not checked in the free run.

    • cites [20] Duewell, 2010, NLRP3 inflammasomes are required for atherogenesis and activated by cholesterol crystals, Nature source

      Not checked in the free run.

    • cites [22] Hornung, 2008, Silica crystals and aluminum salts activate the NALP3 inflammasome through phagosomal destabilization, Nat Immunol source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Volcanic ash can contain a substantial respirable component.

    “Volcanic ash comprises a wide range of particle sizes depending on the fragmentation efficiency of the eruption (35), but can contain a substantial respirable component (31).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [31] Horwell, 2007, Grain size analysis of volcanic ash for the rapid assessment of respiratory health hazard, J Environ Monit source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Cristobalite forms by secondary mineralization or hydrothermal alteration in these environments and is not present in primary magmatic ejecta.

    “This is because cristobalite forms by secondary mineralization or hydrothermal alteration in these environments and, therefore, is not present in primary magmatic ejecta.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [5] Baxter, 1999, Cristobalite in volcanic ash of the Soufriere Hills Volcano, Montserrat, British West Indies, Science source

      Not checked in the free run.

    • cites [6] Horwell, 2013, The nature and formation of cristobalite at the Soufrière Hills volcano, Montserrat: implications for the petrology and stability of silicic lava domes, Bull Volcanol source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Cathepsin B is a well-described player involved in NLRP3 activation.

    “The cathepsin family comprises multiple proteins involved in IL-1β processing with cathepsin B being a well-described player involved in NLRP3 activation (22, 47).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [22] Hornung, 2008, Silica crystals and aluminum salts activate the NALP3 inflammasome through phagosomal destabilization, Nat Immunol source

      Not checked in the free run.

    • cites [47] Hoegen, 2011, The NLRP3 inflammasome contributes to brain injury in pneumococcal meningitis and is activated through ATP-dependent lysosomal cathepsin B release, J Immunol source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The funding bodies had no input into the design of the study, collection, analysis and interpretation of data, or writing of the manuscript.

    “The funding bodies had no input into the design of the study, collection, analysis and interpretation of data, or writing of the manuscript.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The authors declare no conflict of interest.

    “The authors declare no conflict of interest.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Endocytosis and cathepsins are involved in the induction of IL-1β secretion, indicating that lysosomal maturation with subsequent rupture and loss of lysosomal contents into the cytosol is one major mechanism of volcanic ash-induced inflammation in vitro.

    “We show that endocytosis and cathepsins are involved in the induction of IL-1β secretion, which indicates that lysosomal maturation, with subsequent rupture and loss of lysosomal contents into the cytosol, is one major mechanism of volcanic ash-induced inflammation in vitro.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Volcanic ash exposure can result in general insult with the potential for chronic toxicity by inciting a low but significant pro-inflammatory response and resulting in delayed inflammation in vivo.

    “There is mounting evidence that, while not overtly toxic, volcanic ash exposure can result in general insult with the potential for chronic toxicity by inciting a low, but significant, pro-inflammatory response and resulting in delayed inflammation in vivo (10, 11).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [10] Damby, 2016, The in vitro respiratory toxicity of cristobalite-bearing volcanic ash, Environ Res source

      Not checked in the free run.

    • cites [11] Lee, 2004, Montserrat volcanic ash induces lymph node granuloma and delayed lung inflammation, Toxicology source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Internalization of volcanic ash by macrophages induces lysosomal damage and reactive oxygen species (ROS).

    “Internalization of volcanic ash by macrophages induces lysosomal damage and reactive oxygen species (ROS).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The presence of a reactive cristobalite surface has been implicated in the binding of similar proteins by cristobalite-rich volcanic ash and a crystalline silica standard.

    “Nano-scale chemical and structural investigations of surface-exposed cristobalite crystals reveal no evidence for occlusion (8), and the presence of a reactive cristobalite surface has been implicated in the binding of similar proteins by cristobalite-rich volcanic ash and a crystalline silica standard (61).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [61] Jones, 2011, The bioreactivity of the sub-10 µm component of volcanic ash: Soufrière Hills volcano, Montserrat, J Hazard Mater source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Crystalline silica reactivity may be contingent on fracturing the surfaces of crystals in equilibrium.

    “Crystalline silica reactivity may be contingent on fracturing the surfaces of crystals in equilibrium (60).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [60] Turci, 2015, Revisiting the paradigm of silica pathogenicity with synthetic quartz crystals: the role of crystallinity and surface disorder, Part Fibre Toxicol source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Particulate substances or fibers are likely candidates for the initiation of ROS.

    “Particulate substances or fibers are likely candidates for the initiation of ROS (19).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [19] Dostert, 2008, Innate immune activation through Nalp3 inflammasome sensing of asbestos and silica, Science source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Lysosomal uptake is the main uptake mechanism leading to lysosomal rupture with subsequent IL-1β release.

    “The data further reveal that lysosomal uptake seems to be the main uptake mechanism leading to lysosomal rupture with subsequent IL-1β release.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Incorporation of structural aluminum at an equivalent dopant concentration suppresses cristobalite reactivity.

    “incorporation of structural aluminum at an equivalent dopant concentration has been shown to suppress cristobalite reactivity (15), and may affect the presence of certain surface moieties (i.e., silanols) deemed critical for crystalline silica reactivity (62).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [15] Nattrass, 2017, The effect of aluminium and sodium impurities on the in vitro toxicity and pro-inflammatory potential of cristobalite, Environ Res source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    This study was carried out in accordance with the Ethics Committee of the Ludwig-Maximilians-University of Munich.

    “This study was carried out in accordance with the Ethics Committee of the Ludwig-Maximilians-University of Munich (24.02.2006GP/cp).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The NLRP3 inflammasome as an ash-responsive element appears to be predominantly mediated by the crystalline silica phase (cristobalite), although other phases induced a low-level response.

    “The NLRP3 inflammasome as an ash-responsive element appears to be predominantly mediated by the crystalline silica phase (cristobalite), although other phases induced a low-level response.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Volcanic ash has the capacity to generate large amounts of ROS, largely due to the presence of non-crystalline-silica minerals.

    “Previous work has shown that volcanic ash has the capacity to generate large amounts of ROS, largely due to the presence of non-crystalline-silica minerals (33, 51);”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [33] Horwell, 2003, Surface reactivity of volcanic ash from the eruption of Soufrière Hills volcano, Montserrat, West Indies with implications for health hazards, Environ Res source

      Not checked in the free run.

    • cites [51] Horwell, 2007, Iron-induced hydroxyl radical generation from basalitic volcanic ash, Earth Planet Sci Lett source

      Not checked in the free run.

45 of 45

  • The paper relies on this without support.

    The synthetic pure-phase componentry samples (cristobalite, feldspar, volcanic glass) are representative of the corresponding phases in the volcanic ash sample.

    “Pure-phase mineral samples of the primary components were analyzed alongside MRA5/6/99 to constrain their reactivity in the NLRP3 inflammasome model.”
    “As a representative feldspar, we sourced labradorite (feldspar), an intermediate member of the plagioclase series, from the Bavarian State Collection for Mineralogy (Munich, Germany).”

  • The paper relies on this without support.

    The in vitro responses of murine macrophages and human PBMCs to volcanic ash are relevant to human respiratory health hazard from inhaled ash.

    “Inflammasome activation mediated by inhaled ash and its potential relevance in chronic pulmonary disease was further evidenced in PBMC using the NLRP3 small-molecule inhibitor CP-456,773 (CRID3, MCC950).”
    “A mechanistic understanding of the hazard posed by volcanic ash is needed to resolve the existing conundrum and provide appropriate public health advice during future volcanic eruptions.”

  • The paper relies on this without support.

    In most scenarios, ROS are associate stimulators of particle-induced NLRP3 inflammasome activation.

    “It has been shown that, in most scenarios, ROS are associate stimulators of particle-induced NLRP3 inflammasome activation.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • It is expected that inhaled lunar dust will trigger a cytokine-mediated inflammatory cascade, a process also observed in acute volcanic dust exposure, but whether the effects will include chronic fibrotic changes is unknown.

    “Though it is expected that inhaled LD will trigger a cytokine-mediated inflammatory cascade, a process also observed in acute volcanic dust exposure, whether the effects will include chronic fibrotic changes is unknown36.”

    From Overview of lunar dust toxicity risk (2022) · cites this paper as [36]

    The Discussion reports that volcanic ash induces inflammasome-dependent IL-1β secretion in macrophages, supporting the cytokine-mediated inflammation comparison. But this is principally an in vitro finding, not an observation of a cytokine cascade during acute inhaled volcanic-dust exposure. The paper does not examine lunar dust or establish whether it causes chronic fibrosis; it says the clinical manifestations of volcanic-ash exposure remain unknown. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Light-microscopy ash exposure is reported as both 6 and 4 hours

    Minor

    The Light Microscopy method specifies a 6-hour ash treatment, whereas the Results describe a 4-hour treatment before light-microscopy imaging.

1 of 1

Cites

Flagged first, then by citations

1 of the 63 references couldn’t be matched to a known paper.

Research works printed but not linked: 1

  1. Kerr, 1977, Optical Mineralogy

Cited by

Sorted by citations

Related

Authors
Damby, D. E., Horwell, C. J., Baxter, P. J., Kueppers, U., Schnurr, M., Dingwell, D. B., & Duewell, P.
Affiliations
  • United States Geological Survey (US)
  • Durham University (GB)
  • University of Cambridge (GB)
  • Ludwig-Maximilians-Universität München (DE)
  • LMU Klinikum (DE)
Corresponding author
  • Damby, David E.
  • Duewell, Peter
ORCID
Venue
Frontiers in Immunology
Publisher
Frontiers Media SA
Published
2018-01-22
Volume
8
Pages
2000-2000
ISSN
1664-3224 (ISSN-L)
DOI
10.3389/fimmu.2017.02000
PMC
PMC5786523
OpenAlex
W2787591700
Semantic Scholar
36ce61bb241dc01384d14bdee22a398624ca7b27
Cited by
41
References
63
Citations by year
2026: 2 · 2025: 6 · 2024: 5 · 2023: 4 · 2022: 7 · 2021: 5 · 2020: 2 · 2019: 6 · 2018: 2 · 2017: 2
FWCI
1.33
Type
journal article
Language
en
Open access
Licence
Locations
  • Frontiers in Immunology (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Durham Research Online (Durham University) (acceptedVersion, other-oa)
  • Durham Research Online (Durham University) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Open access LMU (Ludwid Maxmilian's Universitat Munchen) (submittedVersion, cc-by)
Funders
  • European Research Council (247076)
  • FP7 People: Marie-Curie Actions (607905)
  • Deutsche Forschungsgemeinschaft (CRC 1123)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Inflammasome and immune disorders
  • Life Sciences › Immunology and Microbiology › Immunology › Immune Response and Inflammation
  • Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Occupational and environmental lung diseases
Keywords
volcanic ash, NLRP3 inflammasome, cristobalite, crystalline silica, caspase-1, IL-1β, macrophages, lysosomal destabilization, cysteine protease, mitochondrial stress, reactive oxygen species, Soufrière Hills volcano, MCC950, lung inflammation

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-08.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-08.

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