Metabolic Response of RAW 264.7 Macrophages to Exposure to Crude Particulate Matter and a Reduced Content of Organic Matter

Abstract

Exposure to air pollution from various airborne particulate matter (PM) is regarded as a potential health risk. Airborne PM penetrates the lungs, where it is taken up by macrophages, what results in macrophage activation and can potentially lead to negative consequences for the organism. In the present study, we assessed the effects of direct exposure of RAW 264.7 macrophages to crude PM (NIST1648a) and to a reduced content of organic matter (LAp120) for up to 72 h on selected parameters of metabolic activity. These included cell viability and apoptosis, metabolic activity and cell number, ROS synthesis, nitric oxide (NO) release, and oxidative burst. The results indicated that both NIST1648a and LAp120 negatively influenced the parameters of cell viability and metabolic activity due to increased ROS synthesis. The negative effect of PM was concentration-dependent; i.e., it was the most pronounced for the highest concentration applied. The impact of PM also depended on the time of exposure, so at respective time points, PM induced different effects. There were also differences in the impact of NIST1648a and LAp120 on almost all parameters tested. The negative effect of LAp120 was more pronounced, what appeared to be associated with an increased content of metals.

Gene Expression Changes Induced by Exposure of RAW 264.7 Macrophages to Particulate Matter of Air Pollution: The Role of Endotoxins

“…The assessment of the selected parameters was performed after both short-term (4–6 h) and long-term (48 h) exposure. Differentiation of short-term time points in the range of 4–6 h, to our knowledge, does not affect the results of the study, as both our unpublished results and data from the literature [ 23 , 31 ] showed that no significant qualitative changes occurred in in vitro cultures exposed to PM during this time interval.…”

“…Organic components were removed at the Faculty of Chemistry of the Jagiellonian University in Kraków. The acronym, LAp120, was formed for the obtained material with a reduced content of organic carbon (from 9.12 to 1.68 wt%) [ 23 ].…”

“…Our previous experiments showed that PM at a final concentration of 1 µg/mL of the culture medium caused only slight changes in the viability and metabolic activity parameters of the RAW 264.7 cells after both 4–6 and 48 h of exposure. On the other hand, PM at a final concentration of 100 µg/mL caused clear changes after both short-term (4–6 h) and long-term (48 h) exposure [ 23 ]. Thus, the abovementioned concentrations of PM and exposure times were used in this work.…”

“…Cell viability was assessed cytometrically following supravital staining of cells with PI as previously described [ 23 ]. PI is a water-soluble fluorescent probe that diffuses into cells when the plasma membrane has been compromised and stains only damaged cells.…”

“…Our previous studies showed that the standard urban particulate air pollutant material, NIST1648a, depending on the concentration and duration of exposure, induced the synthesis of reactive oxygen species (ROS) and the release of nitric oxide (NO) as well as increased macrophagal cell death in in vitro cultures [ 23 ]. NIST1648a devoid of the majority of its organic compounds, as a result of 2 h of cold plasma treatment, referred to as LAp120, had a greater effect on ROS synthesis and cell death but did not induce NO release.…”