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Effects of Eyjafjallajökull volcanic ash on innate immune system responses and bacterial growth in vitro.

Monick MM, Baltrusaitis J, Powers LS, Borcherding JA, Caraballo JC, Mudunkotuwa I, Peate DW, Walters K, Thompson JM, Grassian VH, Gudmundsson G, Comellas AP - Environ. Health Perspect. (2013)

Bottom Line: In alveolar macrophages, volcanic ash disrupted pathogen-killing and inflammatory responses.In in vitro bacterial growth models, volcanic ash increased bacterial replication and decreased bacterial killing by antimicrobial peptides.These data suggest that volcanic ash exposure, while not seriously compromising lung cell function, may be able to impair innate immunity responses in exposed individuals.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.

ABSTRACT

Background: On 20 March 2010, the Icelandic volcano Eyjafjallajökull erupted for the first time in 190 years. Despite many epidemiological reports showing effects of volcanic ash on the respiratory system, there are limited data evaluating cellular mechanisms involved in the response to ash. Epidemiological studies have observed an increase in respiratory infections in subjects and populations exposed to volcanic eruptions.

Methods: We physicochemically characterized volcanic ash, finding various sizes of particles, as well as the presence of several transition metals, including iron. We examined the effect of Eyjafjallajökull ash on primary rat alveolar epithelial cells and human airway epithelial cells (20-100 µg/cm(2)), primary rat and human alveolar macrophages (5-20 µg/cm(2)), and Pseudomonas aeruginosa (PAO1) growth (3 µg/104 bacteria).

Results: Volcanic ash had minimal effect on alveolar and airway epithelial cell integrity. In alveolar macrophages, volcanic ash disrupted pathogen-killing and inflammatory responses. In in vitro bacterial growth models, volcanic ash increased bacterial replication and decreased bacterial killing by antimicrobial peptides.

Conclusions: These results provide potential biological plausibility for epidemiological data that show an association between air pollution exposure and the development of respiratory infections. These data suggest that volcanic ash exposure, while not seriously compromising lung cell function, may be able to impair innate immunity responses in exposed individuals.

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Effects of volcanic ash exposure on macrophage function. (A,B) Results of Western blot analysis of whole-cell proteins from human alveolar macro­phages cultured for 5 hr with media alone (control) or with ash (20 µg/cm2) from batch A, B, or C. (A) LC3‑II levels indicate an accumulation of auto­phagosomes. (B) Increased ubiquitin (Ub) conjugates are present at all molecular weights. (C) Western blot analysis of human alveolar macrophages exposed to ash (batch B; 20 µg/cm2) for 30 min and then to LPS (100 ng/mL) for 30 min; Phosphorylated (activated) MAP kinases decrease in LPS activation with ash exposure. Ash exposure reduced LPS activation of phospho-ERK, phospho-JNK, and phospho-p38. For (A–C), blots shown are representative of three experiments. (D) Real-time RT-PCR analysis showing TNFα mRNA in human alveolar macrophages exposed to ash (20 µg/cm2) for 30 min and then exposed to LPS (100 ng/mL) for 3 hr; data represent mean ± SE of three experiments. (E,F) Phagocytosis (E) and bacterial killing (F) in rat alveolar macrophages exposed to media alone (control) or to 25 µg/mL ash for 2 hr, primed with 10 ng/mL LPS for 1 hr, and then exposed to PAO1 (2.5 × 106 CFU) for 20 min (phagocytosis) or 110 min (bacterial killing); data shown are mean ± SE of four experiments in triplicate. (E) Phagocytosis was similar in control and ash-exposed macrophages. (F) Bacterial killing was inhibited in ash-exposed macrophages, although not statistically significantly (p = 0.07).
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f2: Effects of volcanic ash exposure on macrophage function. (A,B) Results of Western blot analysis of whole-cell proteins from human alveolar macro­phages cultured for 5 hr with media alone (control) or with ash (20 µg/cm2) from batch A, B, or C. (A) LC3‑II levels indicate an accumulation of auto­phagosomes. (B) Increased ubiquitin (Ub) conjugates are present at all molecular weights. (C) Western blot analysis of human alveolar macrophages exposed to ash (batch B; 20 µg/cm2) for 30 min and then to LPS (100 ng/mL) for 30 min; Phosphorylated (activated) MAP kinases decrease in LPS activation with ash exposure. Ash exposure reduced LPS activation of phospho-ERK, phospho-JNK, and phospho-p38. For (A–C), blots shown are representative of three experiments. (D) Real-time RT-PCR analysis showing TNFα mRNA in human alveolar macrophages exposed to ash (20 µg/cm2) for 30 min and then exposed to LPS (100 ng/mL) for 3 hr; data represent mean ± SE of three experiments. (E,F) Phagocytosis (E) and bacterial killing (F) in rat alveolar macrophages exposed to media alone (control) or to 25 µg/mL ash for 2 hr, primed with 10 ng/mL LPS for 1 hr, and then exposed to PAO1 (2.5 × 106 CFU) for 20 min (phagocytosis) or 110 min (bacterial killing); data shown are mean ± SE of four experiments in triplicate. (E) Phagocytosis was similar in control and ash-exposed macrophages. (F) Bacterial killing was inhibited in ash-exposed macrophages, although not statistically significantly (p = 0.07).

Mentions: Effects of volcanic ash on cell function. Autophagy is an important cellular homeostatic mechanism that clears particulates, protein aggregates, old and damaged mitochondria, and cytosolic bacteria (Gutierrez et al. 2004; Monick et al. 2010). Thus, we examined the effect of ash on homeostatic mechanisms (autophagic vesicles and clearance of ubiquitin-tagged proteins) in human alveolar macrophages exposed to volcanic ash (batch A, B, or C; 20 µg/cm2) using Western blot analysis. Figure 2A shows increased levels of LC3-II with each ash exposure, suggesting that ash either increases generation of autophagosomes or blocks progression of autophagosomes to fuse with lysosomes. To determine which of these was occurring, we analyzed total ubiquitin levels by Western blot analysis. We observed an accumulation of ubiquitin-conjugated proteins in ash-exposed cells (Figure 2B), suggesting that ash exposure may interfere with autophagy in human alveolar macrophages.


Effects of Eyjafjallajökull volcanic ash on innate immune system responses and bacterial growth in vitro.

Monick MM, Baltrusaitis J, Powers LS, Borcherding JA, Caraballo JC, Mudunkotuwa I, Peate DW, Walters K, Thompson JM, Grassian VH, Gudmundsson G, Comellas AP - Environ. Health Perspect. (2013)

Effects of volcanic ash exposure on macrophage function. (A,B) Results of Western blot analysis of whole-cell proteins from human alveolar macro­phages cultured for 5 hr with media alone (control) or with ash (20 µg/cm2) from batch A, B, or C. (A) LC3‑II levels indicate an accumulation of auto­phagosomes. (B) Increased ubiquitin (Ub) conjugates are present at all molecular weights. (C) Western blot analysis of human alveolar macrophages exposed to ash (batch B; 20 µg/cm2) for 30 min and then to LPS (100 ng/mL) for 30 min; Phosphorylated (activated) MAP kinases decrease in LPS activation with ash exposure. Ash exposure reduced LPS activation of phospho-ERK, phospho-JNK, and phospho-p38. For (A–C), blots shown are representative of three experiments. (D) Real-time RT-PCR analysis showing TNFα mRNA in human alveolar macrophages exposed to ash (20 µg/cm2) for 30 min and then exposed to LPS (100 ng/mL) for 3 hr; data represent mean ± SE of three experiments. (E,F) Phagocytosis (E) and bacterial killing (F) in rat alveolar macrophages exposed to media alone (control) or to 25 µg/mL ash for 2 hr, primed with 10 ng/mL LPS for 1 hr, and then exposed to PAO1 (2.5 × 106 CFU) for 20 min (phagocytosis) or 110 min (bacterial killing); data shown are mean ± SE of four experiments in triplicate. (E) Phagocytosis was similar in control and ash-exposed macrophages. (F) Bacterial killing was inhibited in ash-exposed macrophages, although not statistically significantly (p = 0.07).
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f2: Effects of volcanic ash exposure on macrophage function. (A,B) Results of Western blot analysis of whole-cell proteins from human alveolar macro­phages cultured for 5 hr with media alone (control) or with ash (20 µg/cm2) from batch A, B, or C. (A) LC3‑II levels indicate an accumulation of auto­phagosomes. (B) Increased ubiquitin (Ub) conjugates are present at all molecular weights. (C) Western blot analysis of human alveolar macrophages exposed to ash (batch B; 20 µg/cm2) for 30 min and then to LPS (100 ng/mL) for 30 min; Phosphorylated (activated) MAP kinases decrease in LPS activation with ash exposure. Ash exposure reduced LPS activation of phospho-ERK, phospho-JNK, and phospho-p38. For (A–C), blots shown are representative of three experiments. (D) Real-time RT-PCR analysis showing TNFα mRNA in human alveolar macrophages exposed to ash (20 µg/cm2) for 30 min and then exposed to LPS (100 ng/mL) for 3 hr; data represent mean ± SE of three experiments. (E,F) Phagocytosis (E) and bacterial killing (F) in rat alveolar macrophages exposed to media alone (control) or to 25 µg/mL ash for 2 hr, primed with 10 ng/mL LPS for 1 hr, and then exposed to PAO1 (2.5 × 106 CFU) for 20 min (phagocytosis) or 110 min (bacterial killing); data shown are mean ± SE of four experiments in triplicate. (E) Phagocytosis was similar in control and ash-exposed macrophages. (F) Bacterial killing was inhibited in ash-exposed macrophages, although not statistically significantly (p = 0.07).
Mentions: Effects of volcanic ash on cell function. Autophagy is an important cellular homeostatic mechanism that clears particulates, protein aggregates, old and damaged mitochondria, and cytosolic bacteria (Gutierrez et al. 2004; Monick et al. 2010). Thus, we examined the effect of ash on homeostatic mechanisms (autophagic vesicles and clearance of ubiquitin-tagged proteins) in human alveolar macrophages exposed to volcanic ash (batch A, B, or C; 20 µg/cm2) using Western blot analysis. Figure 2A shows increased levels of LC3-II with each ash exposure, suggesting that ash either increases generation of autophagosomes or blocks progression of autophagosomes to fuse with lysosomes. To determine which of these was occurring, we analyzed total ubiquitin levels by Western blot analysis. We observed an accumulation of ubiquitin-conjugated proteins in ash-exposed cells (Figure 2B), suggesting that ash exposure may interfere with autophagy in human alveolar macrophages.

Bottom Line: In alveolar macrophages, volcanic ash disrupted pathogen-killing and inflammatory responses.In in vitro bacterial growth models, volcanic ash increased bacterial replication and decreased bacterial killing by antimicrobial peptides.These data suggest that volcanic ash exposure, while not seriously compromising lung cell function, may be able to impair innate immunity responses in exposed individuals.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.

ABSTRACT

Background: On 20 March 2010, the Icelandic volcano Eyjafjallajökull erupted for the first time in 190 years. Despite many epidemiological reports showing effects of volcanic ash on the respiratory system, there are limited data evaluating cellular mechanisms involved in the response to ash. Epidemiological studies have observed an increase in respiratory infections in subjects and populations exposed to volcanic eruptions.

Methods: We physicochemically characterized volcanic ash, finding various sizes of particles, as well as the presence of several transition metals, including iron. We examined the effect of Eyjafjallajökull ash on primary rat alveolar epithelial cells and human airway epithelial cells (20-100 µg/cm(2)), primary rat and human alveolar macrophages (5-20 µg/cm(2)), and Pseudomonas aeruginosa (PAO1) growth (3 µg/104 bacteria).

Results: Volcanic ash had minimal effect on alveolar and airway epithelial cell integrity. In alveolar macrophages, volcanic ash disrupted pathogen-killing and inflammatory responses. In in vitro bacterial growth models, volcanic ash increased bacterial replication and decreased bacterial killing by antimicrobial peptides.

Conclusions: These results provide potential biological plausibility for epidemiological data that show an association between air pollution exposure and the development of respiratory infections. These data suggest that volcanic ash exposure, while not seriously compromising lung cell function, may be able to impair innate immunity responses in exposed individuals.

Show MeSH
Related in: MedlinePlus