Production of Reactive Oxygen Intermediates by Human Macrophages Exposed to Soot Particles and Asbestos Fibers and Increase in NF-kappa B p50/p105 mRNA
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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 μg/106 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 μg/106 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-κB) by semiquantitative reverse transcription–polymerase chain reaction. One hundred μg Chrysotile B, FR 101, or P 90 induced a significant maximum 4.0-fold up-regulation of NF-κB 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-κB mRNA expression (70%). NF-κB 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-κB (p50/p105) mRNA steady-state level.
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