Related Experiment Videos
Dog pulmonary macrophage metabolism of free and particle-associated [14C]benzo[a]pyrene
Abstract:
Pulmonary macrophages (PM) are involved in the clearance of inhaled particulate matter from the lung. PM also are capable of metabolizing xenobiotics such as benzo[a]pyrene (BaP). The objective of this investigation was to measure the ability of PM isolated from dogs to metabolize BaP coated onto diesel exhaust particles and to compare this metabolism with that of BaP in solution. PM were isolated from male beagle dogs and incubated with 1 microM [14C]BaP (solution or diesel particle coated) for select times up to 48 h. After incubation of PM with [14C]BaP, both the cells and the media were individually analyzed for [14C]BaP metabolites by high-performance liquid chromatography. Total quantities of [14C]BaP metabolites in both the media (125 pmol/10(6) cells) and cells (45 pmol/10(6) cells) increased with incubation time for up to 48 h. BaP-9,10-diol and BaP-7,8-diol were the major metabolites in organic extracts from the culture media, whereas BaP-7,8-diol and BaP-4,5-diol were the major metabolites in extracts of cells. Small quantities of BaP phenols and BaP quinones were detected in both the cells and media. Total quantities of BaP metabolites (20-30 pmol/10(6) cells) were not significantly different when PM were incubated for 24 h with either [14C]BaP in solution or [14C]BaP coated on diesel particles. The data suggest that particles retained in lungs are capable of being acted upon by PM metabolizing enzymes and that the ensuing metabolism may play an important role in the metabolic fate of organic material inhaled on particulate matter.
Insights
Pulmonary macrophages metabolize benzo[a]pyrene (BaP) on diesel particles similarly to BaP in solution. This indicates lung macrophages can process inhaled pollutants, influencing their metabolic fate.
Area of Science:
- Environmental Toxicology
- Cellular Biology
- Respiratory Medicine
Background:
- Pulmonary macrophages (PM) are key immune cells in the lungs responsible for clearing inhaled foreign substances.
- These macrophages possess the enzymatic machinery to metabolize xenobiotics, including polycyclic aromatic hydrocarbons like benzo[a]pyrene (BaP).
- Diesel exhaust particles are a common source of inhaled particulate matter carrying adsorbed organic compounds.
Purpose of the Study:
- To quantify the metabolic capacity of canine pulmonary macrophages for benzo[a]pyrene (BaP) adsorbed onto diesel exhaust particles.
- To compare the metabolism of particle-bound BaP with BaP dissolved in solution.
- To understand the role of PM in the metabolic fate of inhaled pollutants.
Main Methods:
- Isolation of pulmonary macrophages from male beagle dogs.
- Incubation of PM with [14C]BaP, either in solution or coated onto diesel particles, for up to 48 hours.
- Analysis of [14C]BaP metabolites in both cellular extracts and culture media using high-performance liquid chromatography (HPLC).
Main Results:
- Metabolite concentrations in both cells and media increased over the 48-hour incubation period.
- Major metabolites identified in media were BaP-9,10-diol and BaP-7,8-diol; in cells, they were BaP-7,8-diol and BaP-4,5-diol.
- No significant difference in total BaP metabolite quantities was observed between PM exposed to solution-phase BaP versus particle-bound BaP after 24 hours.
Conclusions:
- Pulmonary macrophages can effectively metabolize benzo[a]pyrene adsorbed onto diesel exhaust particles.
- The metabolic activity of PM suggests these cells play a crucial role in processing xenobiotics present on inhaled particulate matter.
- These findings highlight the importance of considering particle-associated contaminants in lung toxicology studies.