ABSTRACT
We hypothesized that aggregates of ultrafine carbon and washed diesel particles impair the ability of alveolar macrophages (AM) to kill bacteria and enhance the AM lipid peroxidation (LPO) of lung surfactant. Rat AM were exposed, 5h, to particles 20 microg/ml. The AM, containing carbon or washed diesel particles, were incubated 2h, with Streptococcus pneumoniae, an American Type Culture Collection (ATCC) strain or clinical isolates. Surviving bacteria were quantified. Surfactant was incubated, 5h, with carbon or washed diesel loaded AM and LPO was measured. The particle load was approximately 1 microg/10(6) AM, representing accepted exposure to ambient particles in Europe. Metal concentrations were 10 to 100 fold higher in washed diesel--than in carbon particles. There was a dose dependent increase in bacterial survival with carbon-loaded macrophages, but not with washed diesel-loaded AM. Clinical isolates had a higher survival rate with carbon-loaded macrophages than the ATCC strain. Surfactant LPO was increased with washed diesel-loaded macrophages (95%) and with carbon-loaded macrophages (55%) compared to controls. High LPO caused by washed diesel-loaded AM reflects their increased oxidative metabolism, probably caused by particle metals. The additional oxygen metabolites maintained bactericidal activity of AM, while corresponding activity was decreased in carbon-loaded AM. Altered functions of AM may explain health problems related to air pollution.
Subject(s)
Carbon/toxicity , Lipid Peroxidation/drug effects , Macrophages, Alveolar , Particulate Matter/toxicity , Streptococcus pneumoniae/growth & development , Animals , Carbon/chemistry , Cells, Cultured , Macrophages, Alveolar/drug effects , Macrophages, Alveolar/metabolism , Macrophages, Alveolar/microbiology , Male , Particle Size , Particulate Matter/chemistry , Phagocytosis/drug effects , Rats , Rats, Sprague-DawleyABSTRACT
We investigated whether exposure of alveolar macrophages to aggregates of ultrafine carbon particles affected subsequent phagocytosis of microorganisms. Human alveolar macrophages were obtained by bronchoalveolar lavage and exposed to aggregates of ultrafine carbon particles or diesel exhaust particles (DEP) for 20 h before measurements of phagocytosis. The particle loads were estimated to be comparable to those of air pollution exposure with established health effects in humans. Phagocytotic activity was measured as attachment and ingestion of four different test particles (amorphous silica particles, yeast cells from Candida albicans, and Cryptococcus neoformans opsonized with specific IgG or fresh serum) that bind to scavenger, mannose, Fc, and complement receptors, respectively. Carbon preloading significantly impaired the attachment and ingestion process (P<0.01) for all particles, except for yeast cells from C. neoformans opsonized with specific IgG. On the average, the accumulated attachment decreased by 30% and the ingested fraction decreased by 10%. Loading of alveolar macrophages with either aggregates of ultrafine DEP or carbon particles impaired the phagocytosis of silica test particles in a similar way. Exposure of human alveolar macrophages to aggregates of carbon or DEP, in concentrations relevant to human environmental exposures, caused significant impairment of phagocytosis of silica particles and microorganisms. The inhibitory effect on particle phagocytosis mediated by four different receptors suggests that air pollution particles cause a general inhibition of macrophage phagocytosis. Such an effect may contribute to increased susceptibility to infections and, for example, result in more exacerbations of asthma and chronic obstructive pulmonary disease.
Subject(s)
Air Pollutants/poisoning , Carbon , Macrophages, Alveolar/drug effects , Macrophages, Alveolar/immunology , Phagocytosis/drug effects , Vehicle Emissions , Adult , Candida albicans/immunology , Cryptococcus neoformans/immunology , Female , Humans , Lectins, C-Type/immunology , Male , Mannose Receptor , Mannose-Binding Lectins/immunology , Middle Aged , Particle Size , Receptors, Cell Surface/immunology , Receptors, Complement/immunology , Receptors, Fc/immunology , Receptors, Scavenger/immunology , Silicon DioxideABSTRACT
Phagocytosis of three types of fluorescein-labeled test particles by rat alveolar macrophages (AM) were studied: spherical silica (3.2 microm), heat-killed Candida albicans (3.8 microm), and heat-killed Cryptococcus neoformans (6.1 microm) opsonized with specific IgG. These particles should attach to scavenger, mannose, and Fc receptors, respectively. Both control AM and AM pretreated for 20 h with interferon-gamma (12.5 or 50 U/ml) were studied. The sum of the number of attached and ingested particles per AM (accumulated attachment) was used as a measure of the attachment process, and the number of ingested particles per AM divided by the accumulated attachment (ingested fraction) was used as a measure of the ingestion process. The average ingestion time (IT), which is also a measure of the ingestion process, was calculated from the experimental data. The ingestion process was independent of the attachment process. IT increased with the time of observation. This is explained by the fact that IT determined from observation times shorter than the whole distribution of IT for a certain particle results in a shorter IT than the real average IT. C. albicans (mannose receptor) had the fastest ingestion process, C. neoformans opsonized with specific IgG (Fc receptor) had ingestion that was nearly as fast, and the silica particles (scavenger receptors) had the slowest ingestion process. Treatment with interferon-gamma markedly impaired the attachment process for all three types of particles (and three types of receptors) but clearly impaired the ingestion process only for silica particles (scavenger receptors).
