Production of reactive oxygen intermediates by human macrophages exposed to soot particles and asbestos fibers and increase in NF-kappa B p50/p105 mRNA

Our plain-English summary of Production of reactive oxygen intermediates by human macrophages exposed to soot particles and asbestos fibers and increase in NF-kappa B p50/p105 mRNA, by R. Oettinger, K. Drumm, M. Knorst, et al (Lung, 1999).

The study

• Authors: R. Oettinger, K. Drumm, M. Knorst, P. Krinyak, R. Smolarski, K. Kienast
• Journal: Lung
• Published: 1999;177(6):343-54
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Alveolar macrophages (AM) play a decisive role in the immunologic defense system of the lung and in inflammatory pulmonary pathomechanisms. AM and blood monocytes (BM) were exposed to chrysotile B, soot FR 101, and Printex 90 (P 90). We evaluated the reactive oxygen intermediate (ROI) release of AM and BM after particle exposure. ROI release was measured by chemiluminescence. Thirty-minute exposure caused a significant (up to 2.5-fold) increase in ROI release of AM (100 micrograms/10(6) cells) compared with control experiments (p < 0.01). Identical exposure conditions for BM resulted in a similar reaction pattern (maximum 2.2-fold increase in ROI release; p < 0.05). After a 90-min particle exposure at concentrations of 10 and 100 micrograms/10(6) cells, we investigated the steady-state level of p50/p105 mRNA encoding for the precursor protein of the p50 subunit of nuclear factor kappa B (NF-kappa B) by semiquantitative reverse transcription-polymerase chain reaction. One hundred micrograms Chrysotile B, FR 101, or P 90 induced a significant maximum 4.0-fold up-regulation of NF-kappa B gene expression in AM and a 3.3-fold up-regulation in BM (p < 0.05). The addition of superoxide dismutase (200 U/ml) to particle- and fiber-exposed macrophages resulted in inhibition of ROI release and a decrease in NF-kappa B mRNA expression (70%). NF-kappa B is an important transcription factor involved in the regulation of numerous genes (e.g., for inflammatory cytokines, and cytokine receptors). These cytokines are supposed to be involved in inflammatory pathomechanisms in bronchial epithelial cells, which result, for example, in chronic obstructive pulmonary disease. Our results suggest that particle-induced ROI release is associated with an increase in NF-kappa B (p50/p105) mRNA steady-state level.

In plain English

This was a laboratory study of human cells, not of people's health. The authors collected alveolar macrophages (scavenger cells from the lung) by lung washing from 7 nonsmoking patients who had had surgery for bronchial carcinoma. They also took blood monocytes from 7 healthy volunteers. In test tubes, cells were exposed at two doses to chrysotile B asbestos fibers and two soot products, FR 101 and Printex 90. After 30 minutes, chrysotile B raised reactive oxygen release up to 2.5-fold in lung cells (p less than 0.01) and 2.2-fold in blood cells (p less than 0.05). FR 101's 1.4-fold rise in lung cells was not statistically significant. After 90 minutes, chrysotile B raised the lung cells' p50/p105 mRNA, the genetic message for a precursor of one part of NF-kappa B, 3.4-fold and 3.5-fold at the two doses. NF-kappa B helps regulate inflammation-related genes, but only this message was measured, not the protein or its activity. Adding the antioxidant enzyme superoxide dismutase reduced both effects. The authors concluded that particle-induced oxygen-radical release is associated with increased NF-kappa B message and may alter inflammatory signalling in the lung.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) experiment on human cells exposed to fibers and particles in test tubes, compared with unexposed control cells
• Who was studied: Alveolar macrophages obtained by bronchoalveolar lavage from 7 nonsmoking patients (1 female, 6 male, mean age 66) with operated bronchial carcinoma (2 small cell, 5 non-small cell) undergoing restaging bronchoscopy in Mainz, Germany. Blood monocytes came from 7 healthy volunteers (5 male, 2 female, mean age 26).
• Exposure: Chrysotile B asbestos fibers and two soot (amorphous carbon) products, FR 101 and Printex 90. Each was tested at concentrations of 10 and 100 per million cells (micrograms per 10^6 cells according to the PubMed abstract), for 30 minutes (oxygen-radical release) or 90 minutes (NF-kappa B p50/p105 mRNA). Some experiments added superoxide dismutase at 200 U/ml.
• Main results:
  • In alveolar macrophages, 30-minute chrysotile B exposure produced a maximum 2.5-fold increase in reactive oxygen intermediate release (p < 0.01).
  • In alveolar macrophages, FR 101 produced a 1.4-fold increase in reactive oxygen release that was not statistically significant (p > 0.05). Printex 90 produced a 2.1-fold increase (p < 0.05).
  • In blood monocytes, chrysotile B produced the largest increase in reactive oxygen release (2.2-fold; p < 0.05).
  • Superoxide dismutase almost completely blocked the oxygen-radical release in alveolar macrophages. With chrysotile B at the higher dose, release was 76,633 ± 10,834 cpm without the enzyme, 28,144 ± 4,322 cpm with it, and 30,187 ± 4,821 cpm in unexposed controls.
  • After 90 minutes, chrysotile B raised p50/p105 mRNA (the message encoding p105, a precursor of the p50 subunit of NF-kappa B) 3.4-fold at the lower dose and 3.5-fold at the higher dose in alveolar macrophages, and up to 2.9-fold in blood monocytes (all p < 0.05).
  • For the soot products in alveolar macrophages, FR 101 gave 2.8-fold (p < 0.05) and 4.4-fold (p > 0.05) increases in p50/p105 mRNA at the lower and higher doses. Printex 90 gave 2.0-fold (p > 0.05) and 4.0-fold (p < 0.05) increases.
  • With superoxide dismutase added at the higher dose, p50/p105 mRNA expression in alveolar macrophages was 36% for chrysotile B, 28% for FR 101 and 36% for Printex 90.
  • Cell damage from the exposures was low: at the higher dose, LDH release by alveolar macrophages and blood monocytes rose by up to 7% compared with controls.
• The authors' conclusion: The authors concluded that their results support the hypothesis that particle-induced oxygen-radical release is associated with increased NF-kappa B mRNA expression, and that this may lead to changes in the cytokine network of the lung. They described this as a possible mechanism suggested by in vitro experiments.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Macrophage, Alveolar Macrophage, Chrysotile, Nuclear Factor kappa B (NF-κB), Superoxide, Cytokine.

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• Cytotoxicity and reactive oxygen species generation from aggregated carbon and carbonaceous nanoparticulate materials — K.M. Garza, K.F. Soto, et al. (2008)

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